Rest In Pieces: MESSENGER Ends Orbital Operations, Impacts Mercury's Surface

Rest In Pieces: MESSENGER Ends Orbital Operations, Impacts Mercury's Surface

The MESSENGER spacecraft, depicted in this artist’s rendering, began studying Mercury in 2011. Today, its mission ended with its impact on the far side of the planet. Image Credit: NASA

Here’s MESSENGER by the numbers:
Years since launching: 10+;
Years in Mercury’s orbit: Four;
Number of orbits: 4,105;
Size of its impact crater: Estimated to be 52 feet wide;
Other spacecraft to orbit Mercury in spaceflight history: Zero.

What a long, strange trip it has been: NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft is no more. The space agency’s flagship Mercury mission ended at 3:26 p.m. EDT, as it struck the planet’s surface on its far side at an approximate speed of 8,750 miles per hour. By 3:38 p.m., no signal was detected by the Deep Space Network (DSN) station in Goldstone, Calif.; if MESSENGER had somehow survived, it would’ve emerged from behind Mercury at that time. The mission was declared at its end at 3:40 p.m. The time of impact and end of mission were confirmed by mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.

NASA’s John Grunsfeld, associate administrator for the agency’s Science Mission Directorate, stated: “Going out with a bang as it impacts the surface of Mercury, we are celebrating MESSENGER as more than a successful mission. The MESSENGER mission will continue to provide scientists with a bonanza of new results as we begin the next phase of this mission— analyzing the exciting data already in the archives, and unraveling the mysteries of Mercury.”

MESSENGER’s final image. From the MESSENGER website: “This afternoon, the spacecraft succumbed to the pull of solar gravity and impacted Mercury’s surface. The image shown here is the last one acquired and transmitted back to Earth by the mission. The image is located within the floor of the 93-kilometer-diameter crater Jokai. The spacecraft struck the planet just north of Shakespeare basin.” Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

The impact comes after a brief “stay of execution,” as last month, according to the MESSENGER website, “the team embarked on a hover campaign that allowed the spacecraft at its closest approach to operate within a narrow band of altitudes, five to 35 kilometers above the planet’s surface.” This allowed the spacecraft to collect extra scientific data concerning the planet’s polar ice and magnetic qualities. MESSENGER’s mission was intended to last only a year, but adjustments in fuel economy extended the spacecraft’s life by three more. Its final orbital correction maneuver was conducted Tuesday, April 28.
During its four years of orbital operations, MESSENGER shed light upon one of the Solar System’s most enigmatic planets. Mercury, due to its temperature extremes, proximity to the Sun, and exposure to solar radiation, poses a challenge to spacecraft. The planet was previously only explored in three flybys performed by the Mariner 10 spacecraft during the mid-1970s. Up until 2011, no other spacecraft dared to tackle Mercury as its subject of study.

Enter MESSENGER, launched aboard a Delta II 7925 rocket from Cape Canaveral Air Force Station’s SLC-17B on Aug. 3, 2004. Traveling 6.5 years before it entered Mercury’s orbit, the spacecraft mapped Mercury extensively, and also returned evidence of ice water present near its poles.
MESSENGER also proved itself to be tough enough to brave the harsh conditions of an alien world: “In addition to its momentous scientific findings, MESSENGER also represented a technological breakthrough in spacecraft design, as it survived a harsh environment for a period much longer than its original lifetime. It employed an innovative ceramic cloth sunshade, designed to protect sensitive spacecraft instruments from extreme temperature excursions. In addition, its orientation was fine-tuned to balance heating conditions.”
Sean Solomon, MESSENGER’s principal investigator and director of Columbia University’s Lamont-Doherty Earth Observatory, gave his thoughts about the end of the mission, while underscoring the intrepid spacecraft’s accomplishments:

An artist’s depiction of BepiColombo, ESA and JAXA’s joint Mercury explorers, scheduled to launch in 2017. Image Credit: ESA

“Today we bid a fond farewell to one of the most resilient and accomplished spacecraft ever to have explored our neighboring planets. Our craft set a record for planetary flybys, spent more than four years in orbit about the planet closest to the Sun, and survived both punishing heat and extreme doses of radiation. Among its other achievements, MESSENGER determined Mercury’s surface composition, revealed its geological history, discovered that its internal magnetic field is offset from the planet’s center, taught us about Mercury’s unusual internal structure, followed the chemical inventory of its exosphere with season and time of day, discovered novel aspects of its extraordinarily active magnetosphere, and verified that its polar deposits are dominantly water ice. A resourceful and committed team of engineers, mission operators, scientists, and managers can be extremely proud that the MESSENGER mission has surpassed all expectations and delivered a stunningly long list of discoveries that have changed our views not only of one of Earth’s sibling planets, but of the entire inner Solar System,” he related.

While MESSENGER’s time has come to an end, the spacecraft has left researchers with a treasure trove of data concerning the Solar System’s least-explored planet. Its findings will be available in NASA’s Planetary Data System for years to come. In addition, a new Mercury mission is scheduled to launch in late-January 2017 from Europe’s Spaceport in Kourou, French Guiana, aboard an Ariane 5 launch vehicle. BepiColombo, a joint European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) mission consisting of two orbiters, will identify the impact crater left by MESSENGER when it commences orbital operations in 2024, twenty years after the launch of its U.S. predecessor.

'The Lord Proctected Grandpa': 30 Years Since Mission 51B (Part 2)

'The Lord Protected Grandpa': 30 Years Since Mission 51B (Part 2)

During the majority of the seven-day mission, Challenger operated in a gravity gradient orientation, with her vertical stabilizer directed Earthward and her starboard wing pointing in the direction of travel. Image Credit: NASA, via Joachim Becker/SpaceFacts.de

Thirty years ago, this week, a seven-man crew with a combined age of 340 years rocketed into orbit aboard Shuttle Challenger on Mission 51B. For seven days, the astronauts—Commander Bob Overmyer, Pilot Fred Gregory, Mission Specialists Don Lind, Norm Thagard, and Bill Thornton, and Payload Specialists Lodewijk van den Berg and Taylor Wang—worked around the clock in two shifts to support 15 life and microgravity science experiments from U.S., European, and Indian researchers in the pressurized Spacelab-3 module. As described in yesterday’s AmericaSpace history article, they became the first U.S. crew to include as many as three over-50s, including the then-oldest man in space, but unbeknownst at the time they came within milliseconds of disaster, soon after liftoff.


For Gregory, his first launch proved exhilarating. “I was very excited,” he told the NASA Oral History Project. “I think I was probably anxious, but certainly not afraid. It was similar to the simulations, but they left out the 5 percent, and that was the ‘wow’! I remember the feeling inside when the main engines started; how it was almost a non-event. I could hear it and I was aware of it, but I looked out the window and saw the tower move back. At least that’s what I thought, but then I realized the orbiter was moving forward and then back, and when it came back to vertical, that’s when those solids ignited and there was no doubt about it: we were going to go someplace pretty fast! I just watched the tower kind of drop down below me and was probably laughing during this timeframe. Since we had trained constantly for failures, I anticipated failures and was somewhat disappointed that there were no failures. That was Challenger and she went uphill, just as sweet as advertised. The sensation of zero-G was like a moment on a roller coaster, when you go over the top and everything just floats. Once we got there, it was business as usual, just as we had practised and performed on the ground.”

For Overmyer, Gregory, and Thagard, the first order of business was pulsing their spacecraft’s twin Orbital Maneuvering System (OMS) engines to position themselves in a 225-mile (360-km) circular path. The orbit was inclined at 57 degrees to the equator to provide greater observation coverage for ATMOS. For Don Lind, the reality of actually traveling into space was surprisingly close to the training. “The simulations are spectacularly accurate,” he said later. “With the motion-based simulators, you even got some of the visceral sensations, because they can move the machine around and give you the sense of onset of zero-G. You can’t hold it indefinitely, but we had flown hundreds of parabolas in the KC-135 aircraft, so we were quite accustomed to those things.”

Challenger roars into orbit on 29 April 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Gregory felt that he was well prepared, “but it took about half a day to adapt to microgravity. The body very quickly adapted to this new environment and it began to change. You could sense it when you were on orbit. You learned that your physical attitude in relation to things that looked familiar to you—like walls and floors—didn’t count anymore and you translated floors and ceilings and walls to your head is always ‘up’ and your feet are always ‘down’. That was a subconscious change in your response: it was an adjustment that occurred up there. You also learned that you didn’t go fast, that you could get from one place to the other quickly, but you didn’t have to do it in a speedy way. The only referencing system that you have are your eyes, so you can look at something and establish it as a reference that you use.”

Following launch, the seven astronauts split into their respective 12-hour teams. Very soon, one of the two squirrel monkeys exhibited the same symptoms—lethargy and loss of appetite, but no vomiting—as humans for the first half of the mission, being hand-fed by Thagard and Thornton at one stage, before recovering completely for the final three days. The second monkey displayed no ill effects. The primates proved to be much less active in space than on Earth, although both they and the rodents grew and behaved normally, were free of chronic stress, and differed from their “controls” on Earth only by way of gravity-dependent variables. The monkeys, in particular, were spoiled, too.

“I think the environment they had come from was a place where they received a lot of attention,” said Gregory. “Norm and I would look into the Spacelab and see Bill Thornton attempting to get these monkeys to do things, like touch the little trigger that would release the food pellets. I could tell they expected Bill to do that for them, even though he was outside, looking in. We looked back one time and could see that the roles were kind of reversed and Bill was doing antics on the outside of the cage and the monkeys were watching!” Thornton and Thagard could view the primates through a window in each of their cages, while a perforated opening gave them limited access to the interior.

The Spacelab-3 research module, pictured aboard Challenger’s payload bay during Mission 51B. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

The rodents’ enclosures were similar to those of the squirrel monkeys, with the exception that they housed two occupants per cage, separated by a partition. Half of the 24 rats were rapidly-growing, eight-week-old juveniles and the remainder were mature 12-week-old adults. Although the animals were maintained in healthy conditions throughout their seven days in orbit, the rats proved not quite as “savvy” as the monkeys in terms of their adaptation to microgravity. Nonetheless, all of the animals were recovered in good physical condition, healthy and free of microbiological contaminants. However, the astronauts returned to Earth with a number of concerns because the animal enclosures leaked food crumbs, monkey and rodent feces, and unpleasant odors. “The later analysis was that primarily it was food,” said Gregory, “though there may have been some contaminants in it. Other than interest in watching it being ejected from the holding facility, I think it was just interest. It was a passing issue; not something that would have caused any disruption in the current activities.”

On the ground, however, it became a big news story. “One anecdote involved this bit of animal dung that escaped from a cage and made its way from the Spacelab module to the flight deck,” Thagard told this author in a March 2006 email correspondence, referring to an object that floated past the commander’s nose. “Bob Overmyer made a comment about it that prompted an editorial page cartoon that appeared in some newspapers. The cartoon depicts a shuttle astronaut saying to a crewmate words to the effect of: I’m not upset, I’m just glad we didn’t have elephants on board!”
Aside from the RAHF tests, the main “operational” focus of Spacelab-3 was fluid physics and crystal growth. Taylor Wang operated his own drop dynamics experiment whilst Lodewijk van den Berg focused on the crystal growth. Eighteen hours into the mission, Overmyer and Gregory maneuvered the shuttle into her gravity-gradient attitude to support six days of fluid physics and crystal growth research.

Taylor Wang’s legs emerge from the Drop Dynamics Module (DDM) as Bill Thornton assists him with his experiment. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Unfortunately, Wang’s DDM experiment shorted out and failed, early in the mission. “Not only that, but I was the first person of Chinese descent to fly on the shuttle,” he wrote later, “and the Chinese community had taken a great deal of interest. You don’t just represent yourself—you represent your family—and the first thing you learn as a kid is to bring no shame to the family. When I realized my experiment had failed, I could imagine my father telling me, ‘What’s the matter with you? Can’t you even do an experiment right?’ I was really in a desperate situation.” On the ground, Lead Flight Director Gary Coen told the crew that it was doubtful that the mission could be extended beyond seven days, since Challenger did not have the additional cryogenic reactant tanks carried by her sister, Columbia. There would be no opportunity for time lost on the troublesome experiments.

In his memoir, Riding Rockets, Mike Mullane did not specifically name Wang, but certainly made reference to the incident. “Its failure severely depressed him and he surrendered to episodes of crying,” Mullane wrote, “but this was just the beginning of his torture. He turned out to be a cleanliness freak. Living aboard the shuttle doesn’t leave its occupants feeling springtime fresh!” In the midst of this discomfort and upset, Wang asked Mission Control for permission to try to repair the DDM and when given the go-ahead he quickly got to work, opening the Spacelab rack, isolating the fault, and completely rewiring part of it. Several dramatic photographs, taken by his crewmates, showed Wang’s legs sticking out into the module as the DDM rack appeared to completely swallow his upper body. He had already threatened not to return home if NASA refused to allow him to fix the DDM, so it proved fortuitous that his bluff was not called.

“I hadn’t really figured out how not to come back,” Wang told a Smithsonian interviewer years later. “The Asian tradition of honorable suicide—seppuku—would have failed, since everything on the shuttle is designed for safety. The knife on board can’t even cut the bread. You could put your head in the oven, but it’s really just a food warmer. If you tried to hang yourself with no gravity, you’d just dangle there like an idiot!”

The patch for Mission 51B, emblazoned with the surnames of the seven-man crew. Image Credit: NASA

With the facility successfully repaired, there was no time for suicide and Wang worked virtually non-stop to complete almost all of his experiments in the last three days of the flight, assisted by his crewmates. The results confirmed several age-old assumptions about the behavior of liquids in a microgravity environment and, in spite of its delayed start, the experiment proved highly successful. Nineteen months later, in the fall of 1986, Wang received NASA’s Exceptional Scientific Achievement Medal in recognition of his “contributions to microgravity science and materials processing in space and for his exceptional contributions as Payload Specialist on Spacelab-3.” Elsewhere, Lind and van den Berg oversaw a range of crystal growth and fluid physics investigations on their respective shifts. “He’d brief me and then he’d go to sleep and when he woke up, I’d brief him on what I’d done during the last shift,” Lind remembered, years later. “That was pretty well worked out ahead of time.”

“I don’t think there was competition,” said Fred Gregory of the relationship between the silver and gold teams, “because the two shifts did two different kinds of science. Each shift had its own area of interest and would pick up any unclosed item from the shift preceding them, but would very quickly transition to the activities on orbit. There were really about four hours a day when there was an interaction between the two. During that time, it would just be a kind of status brief on orbiter problems or issues, any review of notes that had come up from Mission Control or some deviation to the anticipated checklist that we had.”
For Lind, the first Mormon astronaut, the gravity-gradient attitude provided a unique perspective of his home planet. “For the first two days of the flight, I did not take one single minute away from the timeline to just be a tourist,” he recalled, “but, on the third day, I had about ten or 15 minutes with no immediate assignment. I floated down to the flight deck. We were flying in an orientation with the tail always pointed toward the Earth and one wing always pointed forward in the velocity vector. That oriented the windows on the flight deck from the zenith to the nadir and from horizon to horizon, so it was like a Cinerama presentation. Both my wife and I are amateur oil painters. The sensation in space is that you are always right side up, no matter how you’re positioned. ‘Up’ and ‘down’ are just meaningless in space! Intellectually, you know you’re moving very fast, so that orbital velocity will cancel gravity, but the sensation is that you are stationary and the world is rotating majestically below you.”

The crew of Mission 51B pose for the traditional in-flight portrait. From left to right are Fred Gregory, Bob Overmyer, Don Lind, Norm Thagard, Bill Thornton, Taylor Wang and Lodewijk van den Berg. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Gregory found the heavens and Earth fascinating. “You immediately realize you are either a ‘dirt person’ or a ‘space person’,” he said. “I ended up being a space person. It was a high-inclination orbit, so we went very low in the southern hemisphere and I saw a lot of star formations that I had only heard about and never seen before. “I also saw the Aurora Australis, which is the Southern Lights. If you were a dirt person, you were amazed at how quickly you crossed the ground; how, with great regularity, every 45 minutes, you’d either have daylight or dark. The sensation that I got initially was that, from space, you can’t see discernible borders and you begin to question why people don’t like each other, because it looked like just one big neighborhood down there. The first couple of days, I was a citizen of Washington, D.C., but Overmyer was from Cleveland and Don Lind was from Salt Lake City and Norm was from Jacksonville and Lodewijk was the Netherlands and Taylor was Shanghai, so each had their own little location for the first couple of days. After two days, I was from America, and after five days the whole world was our home. You could see this sense of ownership and awareness. We had noticed with interest the fires in Brazil and South Africa and the pollution that came from eastern Europe, but it was only with interest. Then, after five or six days, it was of concern, because you could see how the particulates from the smoke stacks in eastern Europe circled the Earth and how this localized activity had a great effect. When you looked down at South Africa and South America, you became very sensitized to deforestation and how it affected the ecology.”

It has often been remarked on dual-shift Spacelab flights that the only times the entire crew really got together were shortly after launch and just prior to re-entry. “I think on that particular mission, it may have been anticipated that we would prepare a meal and everyone would eat at the same time,” said Gregory. “In reality, that’s not what actually happened. I called it ‘almost grazing’. You would go down and perhaps get a package of beefsteak and heat it and cut it open and eat it. You may stay on the middeck or you may go back up to the flight deck or you would go back into the laboratory and eat as you were doing your other routine duties.”

Their descent into Edwards Air Force Base, Calif., on 6 May 1985, proved to be among the most dramatic memories of the mission for Gregory. “Though it takes 8.5 minutes to get up to orbit,” he said, “it takes more than an hour to re-enter and it feels very similar to an airplane ride. You get an excellent view of the Earth. You’re going pretty fast, but you are not aware of it, because you’re so high. It’s an amazing vehicle, because you always know where you are in altitude and distance from your runway. You know you have a certain amount of energy and so you also know what velocity you’re supposed to land, and you watch this amazing vehicle calculate and then compensate and adjust as necessary to put you in a good position to land. We normally allow the automatic system to execute all the maneuvers for ascent and for re-entry, but as we slow down for landing, it is customary for the Commander to actually fly it in, using the typical airplane controls.”

Challenger touches down at Edwards Air Force Base, Calif., on 6 May 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

The de-orbit burn, lasting closely to 4.5 minutes, began at 8:04:48 a.m. PDT (11:04:48 a.m. EDT) and slowed Challenger sufficiently to drop her out of orbit and set her on course for a touchdown on the west coast of the United States. “Absolutely nominal,” was Overmyer’s description of re-entry at the post-flight press conference. “I sat there with my hand on top of my helmet, with essentially nothing better to do than watch, at least down to Mach 0.9.”

Quipped Norm Thagard in response: “Yeah, but the rest of us didn’t know you were doin’ that, or we’d have been more worried!”
After performing a graceful, 193-degree heading alignment circle turn, Overmyer guided the orbiter to a precision landing on Runway 17 at 9:11 a.m. PDT (12:11 p.m. EDT). Post-mission inspections of the shuttle revealed only superficial damage to her thermal protection tiles. However, following the loss of Challenger in January 1986, the Rogers Investigation would uncover worrisome signs that Mission 51B itself came close to disaster.
 
Post-flight examination of the twin Solid Rocket Boosters (SRBs) indicated erosion of the secondary O-ring seal and highlighted the failure of its primary seal. So serious was the incident—the seals were meant to prevent hot gas leakage from the structure of the boosters—that launch constraints were placed on several missions, later in 1985, but routinely waived.

“The first seal on our flight had been totally destroyed,” recalled Lind in his NASA Oral History, “and the [other] seal had 24 percent of its diameter burned away. All of that destruction happened in 600 milliseconds and what was left of that last O-ring, if it had not sealed the crack and stopped that outflow of gases—if it had not done that in the next 200 to 300 milliseconds—it would have gone. You’d never have stopped it and we’d have exploded. That was thought provoking! We thought that was significant in our family. I painted a picture of our liftoff, then two great celestial hands supporting the shuttle and the title of that picture is Three-Tenths of a Second. Each of [my] children have a copy of that painting, because we wanted the grandchildren to know that we think the Lord really protected Grandpa.

A Long Wait for Space: 30 Years Since Mission 51B (Part 1)

A Long Wait for Space: 30 Years Since Mission 51B (Part 1)

Challenger roars into orbit on 29 April 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Thirty years ago, this week, Challenger was circling the Earth on the first dedicated Spacelab science flight of the shuttle era. For seven days, the crew of Mission 51B—Commander Bob Overmyer, Pilot Fred Gregory, Mission Specialists Don Lind, Norm Thagard, and Bill Thornton, and Payload Specialists Lodewijk van den Berg and Taylor Wang—worked around the clock in two shifts to support 15 life and microgravity science experiments from U.S., European, and Indian researchers in the pressurized Spacelab-3 module. Launching on 29 April 1985, the flight made history by establishing a record of just 10 days between shuttle missions, yet as circumstances transpired it would come within milliseconds of disaster.


Spacelab-3 was actually the second voyage of the joint U.S./European research facility, following the inaugural mission of the pressurized module aboard STS-9 in the fall of 1983. Spacelab-2 was intended to be a Verification Flight Test (VFT) of the unpressurized pallet and igloo combination, but had encountered technical difficulties with the Instrument Pointing System (IPS) and ended up being slipped until after Spacelab-3. Consequently, the module and a Multi-Purpose Experiment Support Structure (MPESS) were loaded into Challenger’s payload bay on 10 April, and the shuttle stack was transferred to Pad 39A at the Kennedy Space Center (KSC) just five days later. (In fact, only three days had elapsed since the launch of Mission 51D.)

During Mission 51B, Challenger would operate in a “gravity gradient” orbit, with her vertical stabilizer directed Earthward and her starboard wing pointing in the direction of travel, in order to ensure a stable microgravity environment and limit the amount of disruptive thruster firings. This would aid Spacelab-3’s vibration-sensitive materials science and fluid physics investigations. In readiness for the mission, the roof-mounted Scientific Window Adapter Assembly (SWAA) was removed and replaced by an aluminum panel, whereas the Scientific Airlock (SAL) was retained to house a French-built very-wide-field camera. Outside, the MPESS would accommodate the Atmospheric Trace Molecule Spectroscopy (ATMOS) and the Studies of the Ionization of Solar and Galactic Cosmic Ray Heavy Nuclei (“Ions”) experiments.

The patch for Mission 51B, emblazoned with the surnames of the seven-man crew. Image Credit: NASA

Twenty hours before launch, on 28 April 1985, a pair of male squirrel monkeys (Saimiri sciureus)—described by Don Lind as “cute”—and 24 “not so cute” male albino rats (Rattus norvegicus) were loaded aboard the Spacelab module. Animal welfare concerns, coupled with the requirement to move the primates and rodents during their “awake” time in order to avoid causing them undue stress, made it important to wait until the latter phase of the countdown before loading them into their cages. It proved an interesting event, since Challenger was oriented vertically on Pad 39A. Working from the shuttle’s middeck, two technicians were gently lowered, one at a time, in sling-like seats down the tunnel into the module. One stayed in the joggle section, while the other entered the Spacelab to await the cages, which were lowered on separate slings. The two-hour process ran smoothly and the cages were installed into dual Research Animal Holding Facilities (RAHFs) on the module’s port side wall.

Spacelab-3’s primary focus was on microgravity research, specifically fluid physics and crystal growth, but an additional life sciences aspect evaluated how well the RAHF could support animals in an environment comparable to a ground-based vivarium. It had long been recognized that effective studies of primate or rodent behavior in space was impossible if their health and well-being were improperly maintained. In addition to water and food—rice-based bars for the rats, banana pellets for the monkeys—the RAHF supplied lighting, temperature, and humidity control functions. During the course of Mission 51B, Challenger’s crew were to work in two 12-hour shifts, with physicians Thagard and Thornton assigned to separate teams to keep watch the animals around-the-clock. NASA hoped to use the RAHF again for several rodent experiments on the Spacelab-4 life sciences mission, planned for launch in the spring of 1987.
Also under test was a Dynamic Environment Measuring System (DEMS) to record the acceleration, vibration, and noise in the cages during ascent and re-entry, and a Biotelemetry System (BTS) to transmit physiological data to the ground from a series of implanted sensors. “The squirrel monkeys adapted very quickly,” Lind told the NASA Oral History Project. “They had been on centrifuges and vibration tables, so they knew what the feeling of space was going to be like. Squirrel monkeys have a very long tail and if they get excited, they wrap the tail around themselves and hang onto the tip. If they get really excited, they chew on the end of their own tail. By the time we got into the laboratory, about three hours after liftoff, they were adjusted. They had, during liftoff, apparently chewed off a quarter of an inch of the end of their tails!” Both monkeys were free of various specified pathogens, and it was mandated that six months before launch they must also be free of antibodies to the Herpes saimiri virus. Although the virus was not known to cause disease in either squirrel monkey or human carriers, problems had been documented in other species and a global search found five Herpes saimiri-free primates. Due to time limitations, NASA only had the opportunity to prepare two of them for microgravity exposure and properly train them to reach the food pellets and activate the water taps in their cages.

The crew of Mission 51B departs the Operations & Checkout (O&C) Building on the morning of 29 April 1985. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

The possibility, however remote, of all seven men becoming infected by herpes was hungrily pounced upon by their peers at the Johnson Space Center (JSC) in Houston, Texas, according to Mike Mullane in his 2006 memoir, Riding Rockets. Several Navy astronauts suggested that as long as the Marine Corps and Air Force members of the crew—a none-too-subtle jab at the respective military services of Overmyer and Gregory—did not “screw the monkeys,” they would be fine. Alongside Overmyer and Gregory were no less than five scientists: Thagard and Thornton were both physicians, whilst Lind was a physicist, Dutch-born van den Berg was a chemical engineer, and Shanghai-born Wang was a physicist. Three of these men were intimately involved in several Spacelab-3 experiments as co-investigators: Lind on an auroral imaging study, van den Berg on a vapor crystal growth system, and Wang on the Drop Dynamics Module (DDM).
In fact, van den Berg was internationally recognized as an authority on vapor-driven crystal growth. As the list of Spacelab-3 Payload Specialist candidates was drawn up, van den Berg and his chief at EG&G Corp., Dr. Harold Lamonds, could only come up with seven names, rather than the required eight. Lamonds told fifty-something van den Berg to volunteer, joking that his age, huge spectacles, and limited physical strength would probably cause him to be dropped in the first round of the selection process. It didn’t. Four candidates were eliminated by the initial screening for scientific competence. He was now down to the final four for a series of physical and mental tests, and he and metallurgical engineer Mary Helen Johnston passed with flying colors, whereas two others fell by the wayside due to possible heart issues. In June 1983, van den Berg and Johnston began training at JSC and in the fall of the following year, against all the odds, van den Berg was formally announced as the prime candidate.

If van den Berg’s ascent to a prime crew was rapid, then the opposite was the case for Don Lind, who had waited 19 years since his selection as an astronaut by NASA in April 1966. Having trained extensively for Skylab, he came within days of flying with Vance Brand on a daring rescue mission to America’s first space station in 1973, but wound up waiting longer than any other NASA-selected astronaut in history to reach actually space. It is a record that Lind still holds to this very day. When he was assigned to Spacelab-3 in February 1983, he expected to fly in September of the following year, but payload delays and shuttle manifest changes caused a slippage to November, then January 1985, and ultimately April, as well as switching orbiters from Challenger to Discovery, then back to Challenger again. With 54-year-old Lind, 53-year-old van den Berg, and 56-year-old Thornton aboard, this was the first U.S. piloted space mission to carry as many as three astronauts above the age of 50.

During the majority of the seven-day mission, Challenger operated in a gravity gradient orientation, with her vertical stabilizer directed Earthward and her starboard wing pointing in the direction of travel. Image Credit: NASA, via Joachim Becker/SpaceFacts.de

As a dual-shift flight, the seven-man crew adopted “sleep-shifting” during their final days on Earth. On the Gold Shift were Overmyer, Lind, Thornton, and Wang, whilst the Silver Shift comprised Gregory, Thagard, and van den Berg. “I was responsible for all the support systems that keep the orbiter functioning,” said Gregory of his role as shift leader. “Norm and I had respective jobs on board, but we, in essence, were the folks who supported the work of the Payload Specialists.” As the flight engineer, Thagard was technically part of the orbiter crew, but his work tended to cross over with that of the scientists working in the Spacelab module, and one of his responsibilities was caring for the rodents and primates on his shift. Lind, meanwhile, was in charge of the activation and deactivation of Spacelab-3 and for the bulk of its experiments, one of which had dictated Mission 51B’s launch time.

Challenger had scarcely an hour available in which to launch on 29 April 1985, with her “window” opening at noon EDT. This was calculated to provide the MPESS-mounted ATMOS instrument with the maximum number of viewing opportunities of the composition of the upper atmosphere during 72 orbital sunrises and sunsets. The ATMOS calibration and observations and a program for the French very-wide-field camera were “front-loaded” into the first day of the mission. Then, about 18 hours after liftoff, Overmyer and Gregory would reorient Challenger for almost six days in a gravity-gradient attitude to provide a suitably quiescent environment for the fluid physics and crystal growth investigations.
With the exception of a hydrogen leak in loading the External Tank (ET) with propellants, the countdown proceeded smoothly until 11:56 a.m. EDT, when, at T-4 minutes, a front-end launch processor failed and prevented the liquid oxygen replenishment valve and vent hood from closing automatically. The clock was held as the valves were manually repositioned and Challenger’s thunderous ascent at 12:02 p.m. was described by NASA as “nominal.”

However, it was not entirely nominal, because during the Rogers Investigation into the loss of Mission 51L in 1986, Bob Overmyer would discover exactly how close his crew came to death that day.

SpaceX Prepares for Latest in Long History of Critical Pad Abort Tests (Part 2)

SpaceX Prepares for Latest in Long History of Critical Pad Abort Tests (Part 2)

The launch escape apparatus pulls an Apollo Command Module (CM) to safety during the Pad Abort Test-2 in June 1965. Photo Credit: NASA

Tomorrow, if all goes well, more than 120,000 pounds (54,430 kg) of thrust will rock Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla., as SpaceX stages the long-awaited Pad Abort Test of its crewed Dragon spacecraft. The test, which is part of the Commercial Crew integrated Capability (CCiCap) contract with NASA and comes only months after SpaceX was awarded a slice of the $6.8 billion Commercial Crew transportation Capability (CCtCap) “pie,” will see eight side-mounted SuperDraco thrusters boost the soon-to-be-piloted capsule to an altitude of 5,000 feet (1,500 meters) and about 6,000 feet (1,800 meters) eastwards, after which Dragon will execute a parachute-guided splashdown in the Atlantic Ocean. Wednesday’s test will be dramatic, indeed, and represents a critical milestone as SpaceX aims to deliver U.S. astronauts to the International Space Station (ISS), aboard a U.S. spacecraft, and from U.S. soil, by mid-2017. Yet it is actually the latest in a long line of pad abort tests over more than five decades, which have served to prove the safety and flightworthiness of U.S. crewed vehicles.


If all goes according to plan on Wednesday morning—and SpaceX has already explained that “Winds above 25 knots and Phase II Lightning are the primary Range weather constraints”—the Pad Abort Test will get underway at 7 a.m., about 22 minutes after local sunrise. “Winds have become gusty out of the east and will remain so for the next couple of days as a low-pressure area develops south-east of Central Florida,” it was highlighted by the 45th Weather Squadron in an update on Monday. “The increase in winds also increases the threat of showers along the Space Coast. Showers will be most prevalent in the morning hours and typically diminish after noon. On Wednesday, the low-pressure area will drift north and east, relaxing the pressure gradient, which will result in lower wind speeds over the Spaceport.” Maximum winds to 5,000 feet (1,500 meters) are expected to be easterly at 20 knots, producing a 70-percent likelihood of acceptable conditions on Wednesday. That probability is expected to improve to 80-percent favourable on the backup day on Thursday, as the low-pressure region continues to move north-west and winds continue to weaken. In the event of a 24-hour scrub, the maximum winds to 5,000 feet (1,500 meters) on Thursday will be north-easterly at 17 knots.

Abort trajectory profile for tomorrow’s Dragon Pad Abort Test. Image Credit: SpaceX

Although the test will occur from SLC-40, which is the same site as used last week for the TurkmenÄlem52E/MonacoSat launch, several key modifications were performed on Thursday, 30 April. Notably, the high-level catenary lines for lightning protection have been removed and a truss structure to support the Dragon vehicle at ground level was installed over the SLC-40 flame trench.
At T-0, the eight hypergolic SuperDraco thrusters, built into the sides of the Dragon, will roar to life and ramp up to their maximum 120,000 pounds (54,430 kg) of thrust. This impetus will propel the vehicle away from SLC-40. “After half a second of vertical flight, Crew Dragon pitches toward the ocean and continues its controlled burn,” SpaceX reported Monday, 4 May. “The SuperDraco engines throttle to control the trajectory, based on real-time measurements from the vehicle’s sensors.” Two seconds into the ascent, the spacecraft will have already attained an altitude of 328 feet (100 meters) and will hit 1,640 feet (500 meters) at five seconds. “The abort burn is terminated once all propellant is consumed,” it was continued, “and Dragon coasts for just over 15 seconds to its highest point about 0.93 miles (1,500 meters) above the launch pad.”

The unpressurized “trunk” will be jettisoned at T+21 seconds and the Dragon capsule will commence a slow rotation, with its base heat shield positioned towards the ground. Four seconds later, the drogue parachutes will be deployed, within a 4-6 second window, stabilizing the vehicle in advance of the unfurling of the three main canopies at T+35 seconds. Current expectations are that the Dragon capsule will hit the waters of the Atlantic Ocean at T+107 seconds, with the impact point predicted about 1.4 miles (2,200 meters) downrange of SLC-40.

During Wednesday’s test, SpaceX hopes to acquire significant data in the areas of Sequencing, Closed-Loop Control, Trajectory and External and Internal Environments. It will demonstrate the proper sequencing of the pad-abort timeline, serving to validate the execution of multiple critical commands in a very short period, as well as testing as many as eight SuperDracos in unison for the first time. It will obtain trajectory data for both maximum altitude and downrange distance from the pad and will gather data on “various internal and external factors to Crew Dragon to help ensure safe conditions for crew transport.” Interestingly, SpaceX also noted that the crash test dummy is actually not nicknamed “Buster”, despite media reports to the contrary and SpaceX Vice President of Mission Assurance Hans Koenigsmann referring to the dummy as such during last Friday’s press briefing. “Buster the Dummy already works for a great show you may have heard of, called MythBusters,” SpaceX said in a press statement Monday. “Our dummy prefers to remain anonymous for the time being.”

However, Wednesday’s Pad Abort Test is the latest in a long series of such exercises to validate pad systems, booster systems and spacecraft systems, ahead of piloted flights. As described in yesterday’s AmericaSpace article, the Little Joe booster advanced U.S. knowledge of the intricacies of high-altitude abort events in readiness for Project Mercury, and its immediate descendent (the “Little Joe II”) was employed between August 1963 and January 1966 for five unmanned tests of the escape system for the Apollo Command and Service Module (CSM), as America strove to plant human bootprints on the Moon before the decade’s end. Early studies for Little Joe II (initially dubbed “Little Joe Senior”) got underway in mid-1961, not long after the completion of Little Joe’s involvement with Project Mercury. It would be required to support two launches in 1963 for tests in the Max Q region—an area of maximum aerodynamic turbulence upon a launch vehicle’s flight surfaces, typically encountered about a minute into ascent—followed by two very-high-altitude atmospheric aborts and finally a “Confirming Max Q Abort.” In May 1962, General Dynamics/Convair won the contract to develop the Little Joe II vehicle, with White Sands Missile Range, near Alamagordo, N.M., chosen as the launch site.

The A-002 Little Joe II mission delivers a boilerplate Apollo Command and Service Module (CSM) to altitude on 8 December 1964. Photo Credit: NASA

As preparation work got underway, Aerojet-General’s Algol-1D solid-fueled rocket engine—capable of 98,916 pounds (44,870 kg) of propulsive yield—was selected as the main “sustainer” motor, supplemented by a clustered arrangement of six Recruit engines, producing a total thrust of 228,000 pounds (103,420 kg). Resized to accommodate the much larger Apollo CSM, the Little Joe II stood 33.1 feet (10.1 meters) tall—rising to 85.9 feet (26.2 meters), with the payload affixed—and 12.8 feet (3.9 meters) in diameter, with a span across the four aerodynamic stabilization fins at its base of 28.5 feet (8.7 meters). The stack was then topped by the launch escape apparatus, a truncated rectangular pyramid which acted as an intermediate structure between the CSM and the four solid-propellant tower-jettison motors, which produced 155,000 pounds (70,000 kg) of thrust to pull the spacecraft away from a failed booster.

It was agreed that the maiden voyage of the Little Joe II would be for qualification purposes, and in the meantime, by March 1963, the first booster had emerged from production and was delivered to White Sands at the end of April. The Qualification Test Vehicle (QTV) followed in mid-July and was successfully fired from Army Launch Area (ALA)-3 on 28 August, carrying a dummy aluminum shell in the basic shape of the Apollo CSM and an inert launch escape system. In spite of failing to destruct when commanded, due to an improperly installed primacord, the Little Joe II reached a maximum altitude of 4.5 miles (7.3 km), covered a distance of 8.7 miles (14 km) and accomplished its test objectives to determine base pressures and heating on the vehicle.

Six months later, in February 1964, the second Little Joe II arrived at White Sands, and a boilerplate Apollo CSM was installed at the end of March, prior to the “A-001” flight on 13 May. With the six Recruit motors firing for 1.5 seconds and the Algol-1D sustainer operating for 42 seconds, the flight attained an altitude of 3.1 miles (5 km) and at 44 seconds accomplished the first successful abort with a “live” launch escape system. The landing sequence of the spacecraft also ran normally, with the exception of a failure of one of the mortar-deployed main parachutes, which produced a faster than intended landing. A third (“A-002”) mission took place on 8 December and evaluated the effectiveness of the launch escape system at equivalent pressures and stresses to those expected during a Saturn IB or Saturn V ascent.

On 19 May 1965, the fourth (“A-003”) mission failed in spectacular fashion when one of the Little Joe II’s four stabilizing fins failed, inducing an uncontrollable roll and precipitating the disintegration of the vehicle. A subsequent NASA-General Dynamics/Convair investigation revealed that the No. IV fin inadvertently moved into a “hard-over” position, about a second after liftoff, due to an internal mechanical failure. By 2.5 seconds into the flight, the fin had reached a fully deflected position, where it remained until the vehicle disintegrated. Consequently—and a little ironically—what should have been an abort test turned into a real abort situation, although it was executed at low altitude, rather than the intended higher altitude.

“The faster the rocket went up, the faster it spun around,” remembered instrumentation and electronics engineer Gary Johnson in a 2010 NASA oral history, who observed the A-003 failure. “It had six solid-rocket motors … and those six motors all just came apart. We were only a half-mile away from the launch pad and, all of a sudden, these rockets were coming flying in every direction, almost like they were coming back at us, but they weren’t, of course.” However, the launch escape system fired on time and successfully pulled the Apollo CSM away from the blazing booster and it parachuted to safety.

Also watching the ill-fated A-003 ascent was NASA’s Little Joe II Program Manager Milt Silveira and his wife. “The vehicle started to roll, and when it rolled to the point, structurally, [that] it wouldn’t take it, and it blew apart, and then the payload aborted off the launch vehicle,” Silveira told the NASA oral historian in 2005. “So it was a little more realistic than what we thought! It was supposed to go to a hundred miles down, around, and downrange, and it only went about twenty. But it scattered aluminum all over the sky and things like that. It was a very realistic test from that point, even though it wasn’t the planned one.”

The SpaceX Crew Dragon Pad Abort Test vehicle atop SLC-40 / Cape Canaveral AFS, Fla. Photo Credit: SpaceX

“The lesson out of that was the abort system to initiate the abort for the spacecraft and the launch vehicle consisted of the opening-up of the circuit between the spacecraft and the launch vehicle to initiate the abort,” added Gary Johnson in his recollection of the events of that day. “When the launch vehicle came apart, that in itself opened up that wiring and automatically initiated the Launch Escape System. The pyros fired to separate the Command Module from the launch vehicle, the launch escape motor went off, the pitch-control motor went off, and it went through the entire sequence, which consisted of tower jettison, deploying the apex cover, putting out the drogue parachutes, putting out the main parachutes and then safely recovering the vehicle. The lesson there was on any future vehicles, one of the abort sensors should be this wiring that goes down to the launch vehicle such that if it ever opens up due to a launch vehicle blow-up or structural break-up, it would automatically, without any other indication, initiate the abort.”

The final, seven-minute-long Little Joe II test (“A-004”) occurred on 20 January 1966, delivering a production Apollo Block I spacecraft (CSM-002) to a peak altitude of 14 miles (23 km) and demonstrating its twin objectives of proper LES orientation/stabilization and full structural integrity of the escape vehicle.
In the meantime, separate tests were also underway to demonstrate the capacity of the launch escape system to pull the spacecraft away from an exploding booster on the pad. Unlike Little Joe II altitude flights, which sought to demonstrate the system’s capability to boost a spacecraft away from a failing booster in high-dynamic-pressure conditions, a pair of Pad Abort Tests, also at LC-36 at White Sands, saw the launch escape mechanism fired at ground level. On 7 November 1963, Pad Abort Test-1 successfully lifted a boilerplate Apollo CSM and attached Launch Escape System (LES) from LC-36. Fifteen seconds into the abort, the LES separated and the CM successfully parachuted to a safe landing. With the exception of soot deposited on the spacecraft’s exterior surfaces and a less-than-predicted stability, the 165-second test was considered a great success, reaching a peak altitude of 1.7 miles (2.8 km). This was followed by a highly successful Pad Abort Test-2 on 29 June 1965, closing out Little Joe’s final involvement with a soon-to-be-piloted spacecraft.

A mockup of NASA’s Orion spacecraft is boosted to altitude on 6 May 2010. Photo Credit: NASA

It would be more than four decades—well into the twilight of the space shuttle era—before a series of pad abort testing of an entirely new U.S. piloted spacecraft took place. Following NASA’s August 2006 announcement that Lockheed Martin would be prime contractor for the Orion spacecraft, the initial contracts were expanded in April of the following year with plans for two tests of a Launch Abort System (LAS). That same month, NASA partnered with the Air Force’s Space Development and Test Wing at Kirtland Air Force Base, near Albuquerque, N.M., to stage a series of tests between 2008-2011 of an mechanism to pull Orion to safety in the event of a launch malfunction. “A total of six tests are planned, pending environmental assessments,” it was reported. “Two will simulate an abort from the launch pad and will not require a booster. The rest will use abort test boosters and simulate aborts at three stressing conditions along the … launch vehicle trajectory.”

Groundbreaking operations for the construction of the abort test pads got underway at the Army’s White Sands Missile Range, near Las Cruces, N.M., in November 2007, and the solid-fueled motor to jettison the LAS was static-fired by prime contractor Aerojet in April 2008. The Pad Abort Test-1 took place at White Sands—the very same location from where the Little Joe II launches originated, so many years earlier—on 6 May 2010. An abort motor, with a momentary 500,000 pounds (226,800 kg) of thrust, burned for six seconds to boost Orion away from the pad. It reached a peak velocity of 540 mph (870 km/h).

Simultaneously, a 7,000-pound-thrust (3,170 kg) attitude control motor was also ignited to provide steering, whilst a jettison motor pulled the LAS away from the capsule to permit parachute deployment and a safe landing. Overall, Pad Abort-1 lasted 135 seconds and Orion was brought to a touchdown about a mile (1.6 km) north of the pad. At the time of writing, an Orion Ascent Abort Test (AA-2) is planned from Space Launch Complex (SLC)-46 at Cape Canaveral Air Force Station, Fla., in 2018.

With SpaceX’s fellow CCtCap winner, Boeing, expected to conduct its own Pad Abort Test in support of its CST-100 spacecraft, sometime next year, ahead of inaugural unpiloted and manned missions in 2017, the roar of abort engines on Wednesday morning promises to be a significant milestone as these new crew-carrying vehicles draw closer to maturity. As cautioned by NASA’s Jon Cowart and SpaceX’s Hans Koenigsmann in Friday’s press briefing, the Dragon Pad Abort Test is a development test, “not a shiny, well-polished Space Shuttle launch.” Its ascent will be neither slow or sedate; rather, it will blaze to 5,000 feet (1,500 feet) in about six seconds, before the capsule plummets back to an oceanic splashdown. “I can hold my breath the entire time,” quipped Koenigsmann.

However, what we should see on Wednesday morning will draw more than a few uncanny parallels with the Little Joe missions of yesteryear. It will also closely mirror the Beach Abort Test from 9 May 1960, which was described as “a sterling qualification test, but … hardly spectacular to the public.” Speaking back in 1999, Rodney Rose recalled inviting the media to one of the early Little Joe tests. On one occasion, Rose briefed a group of photojournalists about what they were about to behold.

“Well, this is not quite like what you’re used to, guys,” he explained. “This thing goes off pretty fast.”
“No sweat,” came the reply from one of the photojournalists. “We’ll follow that.”

On the morning of the test, however, he zoomed his camera in on the pad … and missed the Little Joe completely, so rapid was its departure and ascent. “Where did it go? Where did it go?” the hapless photojournalist asked Rose. He had failed to appreciate the sheer impetus with which the launch escape system propelled its precious payload away from the booster. “Six G makes a difference,” Rose explained, “because, you know, 1.1 or less G, they take off pretty sedately from the Cape.”

And therein lies the singular lesson of a Pad Abort Test: Whatever happens on Wednesday morning—whether spectacular to the public or not—the lesson is to Watch Carefully.
For one thing is certain: It’ll be fast.

SpaceX Prepares for Latest in Long History of Critical Pad Abort Tests (Part 1)

SpaceX Prepares for Latest in Long History of Critical Pad Abort Tests (Part 1)

The LJ-1B Little Joe mission launches from Wallops on 21 January 1960, carrying “Miss Sam”, the second rhesus passenger, on a critical Pad Abort Test for Project Mercury. Photo Credit: NASA

Following the recent successes of the CRS-6 Dragon launch toward the International Space Station (ISS) on 14 April and last week’s flight of the TurkmenÄlem52E/MonacoSat payload to Geostationary Transfer Orbit (GTO), the roar of rocket engines from Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla., is becoming almost commonplace. However, on Wednesday, 6 May, SpaceX—the Hawthorne, Calif.-based operator of the Falcon 9 v1.1 launch vehicle and recent co-winner of a slice of NASA’s $6.8 billion Commercial Crew transportation Capability (CCtCap) contract—will execute its most ambitious exercise to date, ahead of its 2017 goal to deliver U.S. astronauts to the space station, aboard a U.S. spacecraft, and from U.S. soil, for the first time since the end of the shuttle era. The long-delayed Pad Abort Test of a specially instrumented Dragon spacecraft will last under two minutes from pad departure through splashdown in the Atlantic Ocean, with most of that distance covered in the first 25-30 seconds, but carries profound implications for the future prospects of the Commercial Crew endeavor.


As described by NASA Commercial Crew Partner Manager Jon Cowart and SpaceX Vice President of Mission Assurance Hans Koenigsmann in a briefing at the Kennedy Space Center (KSC), last Friday, the Pad Abort Test will see the launch of a Dragon crew capsule and unpressurized trunk from SLC-40, during a “window” which opens at 7 a.m. EDT Wednesday. Present estimates from the 45th Weather Squadron at Patrick Air Force Base suggest a 50-percent likelihood of rain and a 10-percent probability of lightning in the morning hours, with high surface winds considered a primary violating factor for the Pad Abort Test to go ahead.

The 21,000-pound (9,525 kg) stack will be powered aloft by eight SuperDraco hypergolic thrusters, built into the side walls of the spacecraft. These will produce a combined impulse in excess of 120,000 pounds (54,430 kg) and deliver the Dragon to an altitude of about 5,000 feet (1,500 meters) in about six seconds, before the vehicle executes a parachute-assisted splashdown about 6,000 feet (1,800 meters) to the east, in the Atlantic Ocean. The entire test—from departing SLC-40 to hitting the water—should last no more than two minutes.

An advanced 3D printed SuperDraco engine, the same which will fly on the piloted Dragon spacecraft, conducting qualification testing at the company’s Rocket Development Facility in McGregor, Texas. Eight of these thrusters will propel the Pad Abort Test Dragon away from SLC-40 on Wednesday. Photo Credit: SpaceX

The vehicle is heavily instrumented with gyroscopes, temperature sensors, acoustics sensors and cameras, although much attention has been focused upon the presence of a crash test dummy, nicknamed “Buster”, who will ride aboard one of Dragon’s seven seats. The other seats will be weighted to simulate the presence of a full crew. It is expected that the dummy will be subjected to peak G-loads of up to 4.5 G during the most extreme points of the ascent. Buster’s contribution and those of the other instrumentation will be a critical asset as SpaceX and NASA move towards an In-Flight Abort, later this summer, and full certification of the spacecraft, which is expected to fly unpiloted in late 2016 and in a crewed capacity sometime early the following year.

Pad abort tests in advance of U.S. piloted missions are nothing new and were conducted as long ago as the late 1950s to evaluate escape mechanisms for the Mercury capsule, which sought to transport America’s first man into space. During the build-up to Project Mercury, it was recognized that a relatively inexpensive system was needed to perform a series of tests of the launch abort apparatus and extract the capsule from a failed booster. The result was the “Little Joe”—conceived in the early spring of 1958 by National Advisory Committee for Aeronautics (NACA) engineers Max Faget and Paul Purser—which became the first rocket developed specifically for the purpose of qualifying a piloted spacecraft. Costing $200,000 per unit, Little Joe was five times cheaper than the Redstone booster and more than ten times less expensive than the Atlas.
The vehicle would be propelled by a total of eight solid-fueled engines, usually configured with four large Castor main motors, supplemented by four Recruit auxiliary motors. These were arranged to fire in various sequences, dependent upon the required trajectory of each mission, and were “canted” in order that their respective thrust axes passed through a point about halfway between the centers-of-gravity for the “loaded” and “burned-out” conditions. “I started out playing with the idea of taking four of the largest solid-propellant rockets that we had in our stable at that time,” Purser explained in a 1999 NASA oral history, “and putting them together and firing two of them, and then later firing the other two, to carry the spacecraft up to pretty high speed and altitude and try the separation.”

Little Joe’s exact thrust at the instant of liftoff varied, but its maximum design impulse was around 250,000 pounds (113,400 kg), which made it theoretically capable of lifting a payload of up to 3,940 pounds (1,780 kg) onto a ballistic trajectory with an apogee of close to 100 miles (160 km). In so doing, the booster would closely mirror the kind of aerodynamic conditions that a crewed Mercury-Atlas would encounter during the early stages of its ascent. Meanwhile, Little Joe’s launch abort system was provided by Grand Central Rocket Company’s 1KS52000 rocket motor, equipped with a trio of canted nozzles to pull a “boilerplate” Mercury capsule away from the booster at altitude. This could produce a maximum 52,000 pounds (26,600 kg) of thrust. Finally, the Atlantic Research Corp. provided a tower-jettison motor, which typically generated 785 pounds (356 kg) of propulsive yield and burned for 1.3 seconds.

The LJ-6 test stands ready for launch on 4 October 1959. Photo Credit: NASA

Following its conception, initial design work led to the award of a formal contract in December 1958 to the Missile Division of North American Aviation. Under the terms of the contract, seven Little Joe airframes and one launcher were to be delivered to the Langley Research Center in Hampton, Va.—by now under the control of the newly-formed National Aeronautics and Space Administration (NASA)—at three-weekly intervals, beginning in June 1959. As circumstances transpired, the hardware was delivered slightly ahead of schedule, with the first boosters arriving in Virginia in late May and the final shipment in early October. Each of the two-stage Little Joes stood about 55 feet (16.8 meters) tall and 6.7 feet (2 meters) in diameter and weighed some 43,000 pounds (20,000 kg). The total span across the four wedge-shaped aerodynamic fins at its base, which ensured static stability at velocities of up to six times the speed of sound, was 21.3 feet (6.5 meters).

In fact, it was the presence of this quartet of fins which earned Little Joe its moniker, after a roll of four in craps. “If you’ve ever played dice and you look at the four on a die with rounded corners, and its four dots, just like the four rockets that we had,” recalled Purser. “Little Joe is actually two deuces, but it’s also four and the die with four on it—one die with four spots—and that’s where Little Joe came from.”

The first Little Joe flight (designated “LJ-1”) took place on 21 August 1959 from Launch Area (LA)-1 at Wallops. Described as a “Max Q Abort and Escape Test”, its core objective was to evaluate the performance of the abort system under the most severe dynamic loads anticipated during a Mercury-Atlas launch. However, the test went badly. About 35 minutes before liftoff, the batteries for the rocket’s programmer and destruct system were in the process of being charged. All at once, there came an explosive flash and a roar, which sent the watching photographers and engineers diving for cover. When the smoke cleared, it became apparent that only the capsule/escape tower had launched—on a trajectory very similar to a pad abort, reaching an apogee of about 2,000 feet (610 meters)—whilst the Little Joe booster itself had not fired and remained intact on the ground. Approaching apogee, the clamping ring which attached the escape tower to the capsule was released and pyrotechnics were fired. Overall, the 20-second test traveled a distance of about a half-mile (0.8 km) and the boilerplate Mercury came crashing back to Earth.
Four weeks later, a five-member investigation committee concluded that an electrical leak—variously described as a “transient”, a “ghost voltage” or just a glitch in a relay circuit—had induced the premature ignition of Grand Central’s 1KS52000 rocket motor. The batteries had been charged and, when they attained full capacity, the sequencer for the abort system was actuated. Sensing insufficient altitude, it had responded by firing the squibs and boosting the capsule/escape tower away from the Little Joe. Unfortunately, there was insufficient power in the batteries to jettison the tower and deploy the capsule’s parachutes, condemning both to a watery grave. “It wasn’t the design of the pyrotechnic,” admitted Guy Thibodaux, then-chief of Langley’s High Temperature Materials Branch, “it was the design of the pyrotechnic circuitry, actually, that caused that particular problem.”

“We heard the news a few hours later, both good and bad,” wrote Chris Kraft—then a supervisory aeronautical research engineer at Langley and subsequently a senior figure within NASA management—in his autobiography, Flight. “The test was a failure. But though it wasn’t part of the plan, we knew that the escape system could handle an abort straight from the pad.”

Sam, pictured in his tiny protective suit, just prior to his 4 December 1959 launch aboard LJ-2. Photo Credit: NASA

Although the capsule and the escape tower were lost, the Little Joe remained intact and was utilized again for a repeat test (“LJ-6”) on 4 October 1959. This time, the focus on Max Q performance was deleted and the emphasis was placed instead upon demonstrating the general reliability of the booster itself. A boilerplate Mercury capsule and an inert escape tower were successfully lofted to an apogee of 37 miles (60 km), covering a range of 79 miles (127 km) and reaching 3,075 mph (4,950 km/h), before the Little Joe was remotely destroyed to trial the flight termination system.

With the hardware thus proven, the next phase focused upon the mysterious region of Max Q—the region of maximum aerodynamic turbulence upon the vehicle’s airframe, occurring about a minute into flight—and the next Little Joe (designated “LJ-1A”) was launched on 4 November 1959. The behavior of the boilerplate Mercury capsule’s main and drogue parachute deployment characteristics was a specific mission objective. The eight-minute flight began successfully at 9:30 a.m. EST, with the ascent profile described as “straight and true”, until the Little Joe was out of sight. An on-board sensor was supposed to indicate when the correct abort dynamic pressure had been attained, whereupon the escape tower’s motor would fire. However, for reasons which were never completely understood, the tower did not fire until ten seconds after Max Q. That said, the mission reached a peak altitude of nine miles (14.5 km), covered a range of 11.5 miles (18.5 km) and achieved a maximum speed of 2,021.6 mph (3,254 km/h). The parachute deployment and recovery of the Mercury capsule from the Atlantic Ocean were satisfactory.

Since the next Little Joe (LJ-2) was already committed to conducting a series of aeromedical investigations, a repeat of the Max Q test was delayed until early the following year. As long ago as March 1959, NASA and Air Force personnel had considered flying live organisms aboard several Little Joe missions. At one stage, pigs were considered as test subjects, but were eliminated when it became clear that they could not survive long periods on their backs, and it was ultimately decided to fly a pair of rhesus monkeys (Macaca mulatta), named “Sam” and “Miss Sam”. Their names originated from the acronym of the facility which reared them, the School of Aviation Medicine (SAM) in San Antonio, Texas. The LJ-2 mission sought to understand the performance of the Mercury capsule under high-Mach conditions and low dynamic pressures, as well as ascertaining how well Sam responded to the peculiar microgravity environment.

At 11:20 a.m. EST on 4 December 1959, Sam—and several other biological passengers, including barley seeds, rat nerve cells, neurospora, tissue cultures and small packets of insects—was launched from Wallops and reached a peak altitude of 55 miles (88 km), before his boilerplate Mercury capsule parachuted to a safe splashdown in the Atlantic and recovery by the USS Borie. “At launch, the four Recruit rocket motors and two of the Castor rocket motors fired to give a thrust of about 260,000 pounds (118,000 kg,” noted NASA’s LJ-2 post-flight report. “The Recruits burned out after about two seconds and the two Castors burned out at about 30 seconds. The remaining two Castors ignited at 23 seconds, giving an overlap of about seven seconds for the two stages. These two Castors then thrusted until 58 seconds. The escape tower ignited and pulled the spacecraft away from the launch vehicle.” Shortly afterwards, at 69 seconds, the escape tower was jettisoned and LJ-2 and Sam began their parachute-assisted descent. Sam’s mission lasted just over 11 minutes and traveled a distance of 194 miles (312 km), but had actually attained an altitude about 100,000 feet (30,500 meters) lower than intended, due to a windage error, and experienced three minutes of microgravity exposure, rather than four. Nevertheless, Sam’s mission achieved full success across all three orders of its pre-planned test objectives.

Miss Sam, in her protective suit, is inserted into a fiberglass couch, ahead of her LJ-1B mission in January 1960. Photo Credit: NASA

Seven weeks later, at 9:23 a.m. EST on 21 January 1960, Miss Sam was launched atop the LJ-1B mission, with a scientific emphasis upon testing her nervous system in a series psychomotor performance tasks. She reached a peak altitude of 9.3 miles (15 km), a velocity of a little more than 2,000 mph (3,200 km/h) and a range of 11.7 miles (18.9 km) over the Atlantic Ocean. The escape tower fired successfully, boosting Miss Sam a further 250 feet (76 meters), before the boilerplate Mercury capsule parachuted back to Earth.
Despite being badly shaken by the ignition of the escape tower—which rendered her temporarily unresponsive to stimuli and induced nystagmus, an involuntary rolling of the eyeballs—Miss Sam survived the 8.5-minute flight, experiencing weightlessness for 28 seconds, and was recovered by a U.S. Marine Corps helicopter and returned to Wallops within about 45 minutes. “You have to realize that Little Joe goes off at about 7.5 G, which is a fair lick, going up,” remembered former Project Mercury Landing System Development engineer Rodney Rose in a 1999 NASA oral history, “and then when the escape motor goes off and pulls the capsule off, the animal gets a total negative-to-positive G…of nearly 20 G.” Both rhesus monkeys had been trained to pull levels whenever a light glowed on the instrument panel, receiving banana pellets or electric shocks for correct or incorrect responses, but Miss Sam proved unresponsive for 30 seconds. “In spite of the shots of electricity to her foot,” recalled Rose, “she refused to work until the drogue chute came out and then she started hitting the button again.”

Betwixt the safe return of Miss Sam and the next Little Joe flight, NASA undertook a “Beach Abort” from Wallops. Unlike its immediate predecessors, which had sought to gather data prior to and during an in-flight abort from the booster, this test instead focused on the performance of the escape, parachute and landing systems, together with recovery operations, in an abort executed directly from the launch pad. On 9 May 1960, a boilerplate Mercury capsule and attached escape tower were fired from ground level—in a fashion not wholly dissimilar from Wednesday’s Dragon Pad Abort Test—and attained a peak apogee of 2,465 feet (751 meters), traveling a little more than a half-mile (0.8 km) in 76 seconds. The Beach Abort have proven highly successful. “The only significant defect noted from this test,” NASA reported in the aftermath, “was a relatively poor separation distance when the [escape] tower jettisoned.”

A perfect splashdown of the LJ-5B mission on 28 April 1961, just one week ahead of Al Shepard’s launch, successfully closed out Little Joe’s involvement in Project Mercury. Photo Credit: NASA

With five Little Joe missions thus completed, the next flight (LJ-5) carried an actual Mercury capsule from prime contractor McDonnell’s production line and was launched from Wallops at 10:18 a.m. EST on 8 November 1960. This particular mission had been in the planning stages for over a year and was designed as the first qualification of an actual production Mercury to sustain abort conditions within the region of Max Q. However, frustratingly, the mission failed when the escape tower motor and the tower-jettison motor both fired prematurely, some 15.4 seconds after liftoff, and the entire Little Joe/capsule—which reached a peak altitude of just over ten miles (16 km)—was destroyed when it hit the waters of the Atlantic Ocean, a mere two minutes later. Salvage operations recovered about 60 percent of the booster and about 40 percent of the capsule.

A follow-up test, LJ-5A, launched at 11:49 a.m. EDT on 18 March 1961, also met with misfortune when it too suffered a premature ignition of its escape tower motor, 43 seconds into the ascent. “The capsule tumbled immediately upon separating and narrowly missed the booster as it decelerated,” recalled Warren North, then-chief of Manned Satellites at NASA Headquarters in Washington, D.C. “The retropack and escape tower were inadvertently jettisoned or torn off as the capsule tumbled. Apparently, the centrifugal force and/or the escape tower removed the [capsule’s] antenna canister, deploying both the main and reserve parachutes.” The parachutes—which would endure aerodynamic loads six times higher than expected—opened at 40,000 feet (12,200 meters) and the capsule splashed down in the Atlantic, having incurred relatively minor damage.

The 5.5-minute mission reached an altitude of 7.7 miles (12 km) and attained a maximum speed of 1,783 mph (2,869 km/h). Subsequent investigation revealed that both LJ-5A and LJ-5A failed principally due to structural deformations near to the clamp rings which fouled the electromechanical separation systems.
The capsule was recovered and repaired, before flying again on the final Little Joe mission, LJ-5B, which flew at 9:03 a.m. EDT on 28 April 1961, only a week before a Redstone booster was destined to deliver America’s first man into space. On this occasion, the vehicle and Mercury capsule performed virtually as intended, achieving a peak altitude of 2.8 miles (4.5 km), a range of nine miles (14 km) and a maximum speed of 1,780 mph (2,865 km/h). Despite a four-second delay in the firing of one of Little Joe’s motors, and a consequently low-pitched trajectory, the 5.5-minute flight succeeded in its core test objectives and proved that the escape system could perform under the harshest aerodynamic conditions anticipated in a piloted Mercury mission.

Of course, NASA was keenly aware that the Soviet Union was closing on its own goal of launching a man into space. “There was a move afoot to put Al Shepard in a Little Joe, because we knew the Russians were going to go,” remembered Rodney Rose. “Some people were pushing to just put Shepard in a couch with a bottle of oxygen and a mask and send him off on a Little Joe, because it did basically the same flight as his Mercury flight did. That got squashed by Headquarters; they said “This is a scientific program, not a publicity stunt!” So we didn’t do it, and the Russians beat us into space.”

Spitzer Space Telescope Discovers Distant Exoplanet Across the Milky Way

Spitzer Space Telescope Discovers Distant Exoplanet Across the Milky Way

Utilising NASA’s Spitzer Space Telescope, astronomers have discovered a distant exoplanet located 13,000 light-years away, through gravitational microlensing. The red cone in the map above our Solar System, depicts the extend in the galaxy of the thousands of known exoplanets that have been discovered by NASA’s Kepler space telescope, while the red circle represents the extend of all the exoplanets that have been detected so far by ground-based telescopes. The white dots show the positions of exoplanets that have been discovered through the gravitational microlensing technique. Image Credit: NASA/JPL-Caltech

In the fictional Universe of Star Trek: Voyager, the crew of a Federation starship comes in contact with the denizens of planetary systems many thousands of light-years away from Earth, while being stranded on the far side of the galaxy. In an example of life imitating art, astronomers have been able to discover dozens of exoplanets across the Milky Way in recent years, through the use of gravitational microlensing. A research team has recently added one more member to the list, by announcing the detection of an exoplanet at a distance of approximately 13,000 light-years away, which was spotted by NASA’s Spitzer space telescope in conjunction with a ground-based deep-sky survey.


As described in a previous AmericaSpace article, gravitational lensing is an effect of the curvature of space-time by gravity that was first described by Einstein’s theory of General Relativity in the early 20th century and can be described as the phenomenon of the bending of light of distant, faraway cosmic sources (like quasars and other distant galaxies) from the gravity of massive objects (like galaxy clusters) that lie in between. The gravity of these intermediate objects bends and refocuses the light of the more distant sources, acting like a lens which brightens and magnifies the latter, thus allowing us to observe distant parts of the Universe that would otherwise be beyond our view. Gravitational microlensing on the other hand, results from the bending of light from much smaller and less massive stellar-type objects like brown dwarfs, red dwarfs, neutron stars and black holes. Because the mass and size of the latter is many orders of magnitude smaller compared to that of galaxies, they brighten the light of passing background objects significantly less, making them much more challenging for astronomers to detect.

The 1.3-m Warsaw University Telescope used by the OGLE survey. Image Credit: OGLE

Despite these observational challenges, astronomers have nevertheless successfully spotted many thousands of such microlensing events as part of various comprehensive deep-sky surveys during the last couple of decades which have monitored hundreds of millions of stars for many years at a time, like the MACHO Collaboration project, the Microlensing Observations in Astrophysics, or MOA, and the Optical Gravitational Lensing Experiment, or OGLE. These have provided great advances to many important areas of astrophysical research, like the study for the nature of dark matter in the halos of the Milky Way and its neighboring galaxies, the characterisation of thousands of variable stars, and the search for exoplanets.
Contrary to the radial velocity and transit methods which are more widely used for exoplanet discovery, gravitational microlensing can only be used when the light from a distant, background star is magnified by the gravitational field of a closer, foreground star that happens to pass in front, as seen by our line of sight here on Earth. In the case of two stars without planets, the background star’s brightness will increase as the foreground star passes in front of it and then decrease as the latter moves away, in a predictable way during a period of days or weeks, producing a well-defined light curve. If the foreground star happens to have any planets orbiting it, these will distort and dim the light from the background star in a noticeable way as well, which will help astronomers measure some of their basic properties, like their mass and orbital period. And since both stars must be exactly aligned for this method to work, such exoplanet microlensing events are extremely rare. Nevertheless, astronomers have been able to detect dozens of microlensing exoplanets, proving that this is a viable and important method for the discovery and characterisation of other planetary systems in the galaxy. The OGLE survey, which utilises the 1.3-m Warsaw University Telescope located at the Las Campanas Observatory in Chile, has been at the forefront of this research, by discovering among other things the most distant known exoplanet to date in the Milky Way, located at a distance of more than 22,000 light-years very near the galactic center, while also detecting a candidate planet-like object inside our neighboring Andromeda galaxy, which if confirmed, would be the first discovery ever of a planet outside of our galaxy.

Infographic explaining how the Spitzer Space Telescope can be used in tandem with a ground-based telescope, in order to measure the distances to exoplanets discovered using gravitational microlensing. Image Credit: NASA/JPL-Caltech/Warsaw University University

Now, an international team of astronomers led by Jennifer Yee from the Harvard-Smithsonian Center for Astrophysics and Andrzej Udalski from the Warsaw University Astronomical Observatory, has announced the discovery of an extrasolar world at a distance of 13,000 away towards the direction of the Milky Way’s center, while utilising OGLE simultaneously with NASA’s Spitzer Space Telescope. More specifically, the researchers sought out to determine whether NASA’s infrared orbiting observatory could be used to make space-based parallax measurements of microlensing events soon after they had been recorded from ground-based telescopes. Parallax is a standard method in astronomy for measuring the distance of nearby stars. By observing the shift in the relative positions of stars in the sky relative to Earth as the latter moves in its orbit around the Sun, astronomers can triangulate their distance with great accuracy.

Similarly, Yee’s team used Spitzer throughout the summer of 2014 for an 100-hour pilot observing program, during which they studied a microlensing event of interest that had been previously detected by the OGLE survey in February. By taking advantage of Spizer’s large distance from the Earth, the researchers were able to observe the light curve of the event from the vantage point of the orbiting telescope and study its variations with time in order to check them against similar observations that were conducted at the same time with the OGLE telescope on Earth. Through this process, the astronomers eventually were able to determine that the event was caused by the magnifying of a single star’s light due to the foreground passage of an orbiting planet-type object with a mass of approximately 0.5 times that of Jupiter. Consequently, these observations of the same microlensing event from two different largely separated vantage points allowed Yee’s team to triangulate the distance of the newly discovered planet, named OGLE-2014-BLG-0939L, determining that it was approximately 13,000 light-years away towards the direction of the Milky Way’s central bulge, while the star-planet separation was estimated to be about 3.1 AU.

This plot shows the light curve of OGLE-2014-BLG-0124L, obtained from NASA’s Spitzer Space Telescope and the OGLE survey, during the summer of 2014. The finding was the result of fortuitous timing because Spitzer’s overall program to observe microlensing events was only just starting up in the week before the planet’s effects were visible from Spitzers vantage point. Image Credit: NASA/JPL-Caltech/Warsaw University University

One significant aspect of this discovery is the fact that it’s the first of its kind to be made by an orbiting space telescope. “Spitzer is the first space telescope to make a microlens parallax measurement for a planet,” says Yee. “Traditional parallax techniques that employ ground-based telescopes are not as effective at such great distances.” Furthermore, gravitational microlensing can complement other exoplanet detection techniques like radial velocity and the transit method, which are limited in discovering mostly massive planets in relatively close orbits around their host stars. In addition, the bulk of the thousands of exoplanets that have been discovered to date, have been found within a radius of a few thousand light-years from Earth. Gravitational microlensing opens up the possibility of mapping the vast expanses of the entirety of the Milky Way to really study the distribution of planets across the galaxy and discover planet-type objects that can’t be detected with any of the other planet-hunting methods that are currently being used. “There are several major benefits to such a study,” write’s Yee’s team in its study which appeared in the April 1 issue of The Astrophysical Journal. “First, it is the only way to obtain a mass-based census of stellar, remnant, and planetary populations. Several components of this population are dark or essentially dark including free-floating planets, brown dwarfs, neutron stars, and black holes and therefore are essentially undetectable by any other method unless they are orbiting other objects. In addition, even the luminous-star mass function of distant populations (e.g., in the Galactic Bulge) is substantially more difficult to study photometrically than is generally imagined. For example, a large fraction of stars are fainter components in binary systems, with separations that are too small to be separately resolved, but whose periods are too long (or primaries too faint) for study by the radial velocity technique.” “We’ve mainly explored our own solar neighborhood so far,” adds Sebastiano Calchi Novati, a Visiting Sagan Fellow at NASA’s Exoplanet Science Institute at the California Institute of Technology in Pasadena Calif, and co-author of the study. “Now we can use these single lenses to do statistics on planets as a whole and learn about their distribution in the galaxy.”

The proposed WFIRST-AFTA mission will greatly complement any present and future planet-hunting missions, by allowing astronomers to map the distribution of exoplanets throughout the galaxy. Image Credit: NASA/WFIRST/Matthew Penny (Ohio State University)

Bearing that in mind, the latest Astronomy and Astrophysics Decadal Survey by the National Research Council in 2010, acknowledged the proposed Discovery-class Wide Field Infrared Survey Telescope-Astrophysics Focused Telescope Assets mission, or WFIRST-AFTA for short, as a top priority for the 2020’s. One of the main science objectives of WFIRST-AFTA mission proposal, which calls for using one of the two 2.4-m telescopes that were donated to NASA by the National Reconnaissance Office in 2012, is to provide a complete census of exoplanets throughout the galaxy through the use of gravitational microlensing. “WFIRST addresses fundamental and pressing scientific questions and will contribute to a broad range of astrophysics”, wrote the NRC’s Astro2010 Decadal Survey. “It complements the committee’s proposed ground-based program in two key science areas: dark energy science and the study of exoplanets.” If WFIRST-AFTA gets the final go-ahead by NASA for implementation, it could open up a new chapter in exoplanet research as a follow-up to the science results by ESA’s Gaia space observatory which has already began its primary 5-year mission, as well as the James Webb Space Telescope which is scheduled for launch in 2018.

“We don’t know if planets are more common in our galaxy’s central bulge or the disk of the galaxy, which is why these observations are so important,” says Yee. Provided that NASA goes forward with the WFIRST-AFTA mission proposal and the space agency receives the funding necessary for the next round of Discovery-class missions, the 2020’s will truly constitute a new golden era in exoplanetary research, bearing discoveries that are unimaginable today.