Good afternoon everyone! It's a little late to be that time, but it is nonetheless. Between me being up rather later than I should have been watching Twitch Plays Pokemon and Workable Goblin struggling with some of the technical content of this post (asteroid and comet target selection is a serious issue, due to the shear number of bodies possible as targets), this post wasn't ready to go up earlier today. However, now it is, and now it shall!
Eyes Turned Skywards, Part III: Post #23
By the early 1960s, it had gradually become clear that asteroids and comets, the “minor planets” of the astronomer, could be a potentially lethal threat to life on Earth. First the scientific community, then the general public became aware of the potential danger of a rock from space striking with the equivalent energy of hundreds to millions of nuclear bombs going off at once. Such power could level vast areas, raise enormous tsunamis to scour clean whole ocean basins, and even throw thousands of tons of debris into the atmosphere, dimming the sun’s light and cooling the Earth for years. Depending on the size of the rock, millions to billions of people could die, and civilization along with them.
Despite the magnitude of the possible threat, and a spate of disaster movies and science-fiction novels relying on the threat of an imminent impact for their plot in the late 1970s, by the early 1980s fear of impacts had faded among the public. The closer and hence more threatening spectre of nuclear war had once again raised its head, and just as the first spaceflights to minor planets were taking place, and palaeontologists were beginning to take seriously the possibility that impacts might have been responsible for past mass extinctions, interest had dropped to an all-time low.
It took Comet Galileo to dispel the cloak of obscurity that the entire field had been languishing in for the better part of a decade. Even before the comet’s discovery, Congress had been funding a study into the threat of asteroid impacts, perhaps as a result of lessening Cold War tensions. Shortly afterwards, the report, termed the “Spaceguard report” after an organization featured in Arthur C. Clarke’s Rendezvous with Rama, was published, recommending a fairly modest program to detect more of the near-Earth asteroid population, and identify any potentially threatening impactors. In the environment of an ongoing election campaign, and then with the switch to the new Gore administration, the report fell into obscurity, but the ideas it contained were merely dormant, not totally lost.
With NASA busy reorganizing itself under the pressure of its new administrator, further action on the impact threat would have to wait for Galileo to hit Jupiter in 1994. Images of the gigantic scars left by the comet’s fragments, many big enough to envelop the entire Earth, were broadcast around the world and even distributed on the burgeoning medium of the Internet, lending a new plausibility to the old disaster movie plot. Shortly afterwards, Gore announced that his administration would be working on methods to minimize the possible danger posed by asteroids and comets to Earth.
To begin with, this would consist simply of the sort of program advocated by the Safeguard report, a government-funded observation program to identify near-Earth asteroids and comets and determine whether any of them might be a threat to Earth. Astronomers were well aware that only a small fraction of objects on Earth-crossing orbits had ever been observed, and identifying any possible threats had always been considered the first step for any asteroid deflection program. However, Gore wanted to go above and beyond simply funding telescopes. From the beginning of his administration, it had been clear that he had a passion for attempting to improve the functioning of the government, and the comets and asteroids offered another ripe field for experimentation.
The problem, in essence, was that planetary exploration was getting too expensive. Since the 1970s, California’s Jet Propulsion Laboratory had dominated robotic planetary exploration in the United States, and had spearheaded a series of highly successful missions--Viking, Voyager, Kirchhoff, Galileo, the Mars Traverse Rovers, VOIR, and Cassini--but for a steep price. Each of these missions had cost over a billion dollars to develop, build, launch, and operate to completion, and costs had only been going up over time, even faster than inflation. Ames, JPL’s Bay Area rival, had had some success operating cheaper missions like Venus and Mars Pioneer, and the Mars Reconnaissance, Lunar Reconnaissance, and Near Earth Asteroid Pioneers, but even their missions had been gradually creeping up in cost as well. This had been well enough in the 1980s, when a relatively flush budget had offered plenty of room for overruns and gold-plating, but in the more straitened environment of the 1990s, with costs to operate Freedom and develop Artemis cutting deep into the budget, the agency simply could not afford more expensive missions, at least not at the rate they had been flying. And yet each of those missions had opened up enough scientific questions for a dozen more probes; even dismissing Saturn as a target, since Cassini had only been launched in 1994 itself, reports produced in the early 1990s listed a plethora of planetary missions scientists wanted. Probes to Europa and Io, the most active of the Galilean moons; an orbiter for Mercury, still only visited by Mariner 10; networks of instruments on the Moon, Mars, even Venus; more expeditions to minor planets, some perhaps returning samples; even sample-return from the Red Planet was on the agenda, despite the cool reception it had gotten from the Gore Administration.
This was a Gordian knot, pitting scientists desperate to go farther against accountants and Congressional delegates equally desperate to keep costs in line, and a perfect place for Gore to once again look for efficiencies in present practice. The most obvious place to start, given the failure of the “common bus” approach used by Ames on its most recent Pioneer missions to significantly reduce costs, was to open up NASA to a little bit of competition. If every mission proposal produced by someone outside of NASA had been stacked up, the results would probably have buried Gore’s desk, if not the entire Oval Office itself, yet no one but NASA had ever flown an American planetary science mission. Interesting concepts, if they were flown at all, were flown by a NASA center. True, the spacecraft themselves were built by outside contractors, but the management was entirely NASA-based. The success of Hubble, which had specifically not been (entirely) managed by NASA, along with a variety of other highly successful NASA programs that depended on NASA facilitating the programs of other organizations, mostly universities and research labs, rather than developing missions themselves, pointed to a new concept of operations. Instead of doing everything in-house, NASA would act similarly to the Department of Energy, maintaining their own research programs while also funding outsiders to design, build, launch, and operate missions. By subjecting proposals to a rigorous cost cap, a popular idea among procurement reformers of the time, uncontrolled cost growth could be controlled, and science could be done for much less money.
Well, in theory at least. In practice, scientists were simultaneously cautious and optimistic about Gore’s proposal; more missions, fulfilling the goals of more scientists would certainly be good, but the cost cap led to a certain degree of skepticism about whether these missions would produce high-quality science, or even be launched (should unexpected issues arise).
It was clear that some kind of proof of concept, a mission undertaken by NASA itself under the new constraints needed to be launched, one that could prove that high-quality science could, indeed, be done on the proverbial shoestring. In many ways, near-Earth comets and asteroids provided the perfect environment for these proving ground missions. Most lie relatively close to Earth, requiring comparatively little delta-V to reach, simplifying command and control, and reducing the size and expense of the booster used to launch missions. Thermal and power demands were also simplified by their inner system location, compared to Mercury or the asteroid belt. And despite previous missions to the minor planets, there were plenty of obvious possibilities for cheap missions.
And, of course, asteroid and comet missions would be relatively easy to sell based on the potential threat posed to Earth. While Spaceguard would have a larger effect on the security of Earth, missions to the minor planets would be more visible, and in some ways just as important. Although many methods of deflecting asteroids had been proposed since the 1960s, many questions remained about the practicality of any of these proposals, and especially how the proposed strategies would interact with asteroidal and cometary internal structure. A nuclear bomb detonating near a monolithic chunk of rock might fragment it, turning a Texas-destroying impact into a hemisphere-devastating one, while the same bomb detonating near a different asteroid, composed of a loosely-bound matrix of rock fragments ranging from boulders to pebbles holding together only from their mutual gravitation might have no effect at all. And while radar observations had been refining estimates of asteroidal properties, there was no substitute for actually visiting asteroids and exploring them directly to quantify their properties.
With targets tacitly selected and program goals largely defined, the next step was to define a list of possible missions. Scientists at Ames, Langley, and Goddard, the three centers selected for an internal competition to design and manage what was expected to be a series of missions, were tasked with analyzing current ideas and previous missions for any opportunities, narrowing the list of possibilities down to just a few relatively simple ones. Each center had their own spin on mission concepts, of course, but in the end they all broadly agreed on which missions made sense and which didn’t.
First to be eliminated were the simplest missions, flybys of single comets or asteroids. With Encke, Halley, Tempel 2, and Anteros already having been visited by spacecraft, there would be little scientific value in another brief encounter. Only slightly longer for the world were missions to rendezvous with further single comets or asteroids; while they would certainly return more scientific data than flybys, and could clarify differences between asteroids or comets of different types, they would still be relatively expensive for what information they provided, and again would duplicate previous missions.
Instead, each of the centers proposed a variant on the idea of multiple flybys or rendezvouses, with different centers proposing different methods of carrying out the mission. Langley’s expert astrodynamicists proposed a multiple flyby mission, exploiting multiple passes by Earth, Venus, and Mars to visit a series of asteroids and comets, while Goddard, in conjunction with Lewis Research Center in Ohio and their electric propulsion masters proposed a multiple orbiter mission, using the unparalleled efficiency of ion drives to slowly travel from target to target, much like Europe’s ongoing Piazzi mission. Ames, less invested in either approach, proposed to split the difference, utilizing a combination of ion propulsion and gravity assists to flyby and rendezvous with several destinations. By comparing data on multiple objects, especially ones of different spectral type, and particularly data from the same instruments, the first comparative studies of near-Earth objects could be performed. Differences in structure that might be relevant for planetary protection could be explored, and a much greater scientific value for the cost could be had than with a simpler and more straightforward mission, without actually increasing that cost very much.
The logical next step, once a reasonable variety of minor planets had been visited, would be to land on some of them. Here, the centers had much less disagreement among themselves, all proposing more or less the same concept of a self-contained, solar powered spacecraft capable of firmly anchoring itself to the tiny worlds it would be visiting. By avoiding radioisotope thermal generators the cost would be greatly reduced, although in exchange the selection of targets would also be narrowed; while plenty of asteroids were available, most known comets traveled too far from the sun for solar-powered landers to operate at their aphelion, at least without making them very large or very simple, while perihelion, with its burst of cometary activity, would be too dangerous to attempt a landing in any case. Nevertheless, enough targets remained that all three were confident a practical one could be found for the comet’s lander.
Once orbiting and landing missions had been completed, most scientists thought the next step should be returning samples of the minor planets to Earth, where laboratories equipped with the latest and greatest instruments, including those developed years or even decades later, could intensively study returned material, producing far more data than ever possible from virtually any number of ordinary missions. Given the low gravity and small size of minor planets compared to ordinary planets, especially the Moon and Mars, it was even possible to contemplate launching sample return missions on the budget Gore’s nebulously defined new program would allow, and all three centers duly proposed them. As with the multiple flyby/rendezvous mission, however, each had a slightly different take on the idea.
Langley, still enamoured by its astrodynamic wizardry, proposed a unique twist on the sample return concept to kick off its series of sample return mission. After the multiple flyby mission, the spacecraft used for it would be modified with a sample collection grid on its forebody, then sent to fly through the coma of an active comet. Cometary dust safely ensconced within the structure, it would be packaged inside a reentry capsule and returned to Earth for study. After this mission, two more would see scaled-up versions of Langley’s lander carrying sample collection instruments and a sample return vehicle dispatched to different objects to collect surface samples. For the cometary mission, specially-designed coolers would provide a cryogenic environment from launch to curation, preserving the sampling environment after collection.
As before, Goddard took a completely different tack, again in collaboration with Lewis. Like Langley, they envisioned reusing the multiple orbiter spacecraft, this time to transport a lander modified with a small sample launch vehicle to any of a number of destinations. Once sample collection was completed, the orbiter would collect the sample container and return it to Earth. By using efficient ion propulsion, more targets could be reached than possible in Langley’s ballistic proposal, and without too much of a price increase; while the complex orbiter increased costs, these were partially offset by a simpler lander and smaller launch vehicle. A mission might even be able to test techniques proposed for minimizing the risk from Mars samples, braking into Earth orbit for sample retrieval by a later Apollo mission or collection and curation at Freedom. Unlike Langley, however, Goddard made no proposal to collect samples from the coma of a comet, preferring instead to focus purely on surface samples.
Ames, meanwhile, continued its trend of standing in between the two. Like Langley, it proposed using direct-return landers, with no separate orbiter element, but like Goddard it ignored the possibility of low-cost coma sample return. Instead, Ames’ proposals mostly focused on minimizing the cost of the landers, going into some detail on possible methods of reusing current developments, enlisting international assistance (Russia in particular was mentioned several times), or saving costs through design.
By the time these studies reached Gore’s desk in mid-1995, the President had more immediate security matters to worry about than asteroid impacts, and it languished for some time before the President brought it up in his FY 1997 budget proposal in early 1996. Between the middle of the previous year and the President’s resumption of interest, a number of changes had been made to the proposed mission sequence, mostly by eliminating proposals that seemed to fit poorly into Gore’s goals for the still-unnamed program. First to go was the multiple comet/asteroid tour mission, with Russia’s Grand Tour mission nearing launch. Largely identical to Langley’s proposed implementation of the mission, duplicating it seemed like a poor scientific value for the cost, despite the low implementation risks.
Next to meet the chopping block had been the comet sample return mission. While scientifically exciting, the complex systems needed to maintain comet surface samples in cryogenic suspension while returning to Earth posed serious development risks, for both time and budget, while the difficult dynamics of reaching most comets would require relatively expensive launch vehicles. For a program intended to demonstrate the possibilities for relatively inexpensive space exploration, the mission was a poor fit at best.
Third up was the coma sample return mission. Initially, this had gotten very positive reviews at Headquarters, where the combination of element reuse and scientifically productive yet simple mission design had been attractive for the same reasons interest in comet sample return had cooled. However, during negotiations with the Japanese over their contributions to the Artemis program, they had mentioned that they were themselves planning a similar mission, and expected to begin a formal program soon--something which indeed obtained formal approval from the Japanese government shortly afterwards. Another derivative of the same basic bus design as Susei and Sakigake, it had a virtually identical mission profile to Langley’s proposal, eschewing complicated electric propulsion or complex sample collection equipment. As with Grand Tour, the presence of a foreign mission made the American version seem less valuable and worth funding.
Of the three remaining mission concepts, returning samples from a near-Earth asteroid stood out as being considerably more complex and likely more expensive than the other two. While Ames, Langley, and Goddard all agreed that it could be done within the desired cost cap, NASA administrators had been less sure, and recommended that the program be structured to attack the simpler lander missions in parallel, while delaying the sample return mission for additional development and study. Of particular interest were methods of further reducing mission cost, such as taking advantage of development for other programs or seeking international partners. France’s CNES had already expressed some interest in partnering with NASA on an asteroid sample return mission, and it seemed entirely possible other partners could be wooed in the future.
Therefore, for the FY 1997 budget NASA had narrowed the proposed Comet and Asteroid phase of what was becoming known as the Pioneer Program into two initial missions, Comet and Asteroid Lander, and one long-term mission, Asteroid Sample Return. The program appealed to Congressional interest in cost-effective exploration, and was easily approved to allow development beginning in late 1996.
Once Congressional approval had been obtained and a budget line created, the first thing Headquarters needed to do was decide which center would actually be responsible for carrying out the planned missions. Given the history of planetary exploration at NASA, it was widely expected only one center would be selected to manage all three missions. At Headquarters, however, thought was proceeding along very different paths, with concerns about how a single center managing the whole program might get, to not put too fine a spin on it, fat and lazy, subverting the cost-saving underpinning of the program.
In a move which surprised nearly everyone, then, Headquarters instead announced that they were dividing up responsibility. The long-term sample return mission would be returned to the centers for study, this time with the Jet Propulsion Laboratory joining Ames, Langley, and Goddard in developing mission concepts. Meanwhile, the asteroid lander and comet lander missions would be divided among Ames, for the first, and Langley, for the second, in the hopes that this division of responsibilities would spur both to do better work, faster and cheaper than their competitor. With its long pedigree of relatively low-cost planetary exploration missions, Ames had been widely viewed as the safe choice among the three, while in turn Langley had been viewed as the moderate--safer than Goddard, which seemed intent on exploiting advanced technology, but more daring than Ames, given its shorter history in the field.
Beyond merely dividing up responsibility among its own centers, Headquarters had returned to actively pursuing foreign involvement, whether that be something as minor as an instrument or two, or as significant and wide-ranging as an entire spacecraft for a Goddard-style sample return mission. The largest success came with bringing CNES, which had already expressed significant interest in the possibility, into the studies being performed by JPL, Ames, Langley, and Goddard, although agencies from Brazil to South Korea had shown interest in some measure of collaboration, and Japan had agreed to provide an instrument for the asteroid lander in exchange for an American instrument for their comet coma mission. While not, of course, part of the developing American Pioneer Program, as it had come to be known, Japan’s mission was widely considered to be part of the same general wave of interest in near-Earth objects, and in some quarters was considered to be virtually a part of the American effort.
As French engineers talked with American scientists about possible collaborations, the sketched-out designs that Ames and Langley had envisioned for their spacecraft began to solidify, confronted with a more concrete reality than before. Both had settled on a simple “box with legs” for their core lander design, intended to tightly grip the surface of a loosely packed asteroid or comet. Langley’s, intended for comets roaming nearly as far out as Jupiter, was noticeably larger than Ames’ design, to accommodate the extra acreage of solar cells needed for power in the dim, cold environs of the outer solar system. Instruments would be mounted on the base of the probe or on its wide, flat sides, as appropriate, while thrusters would hang off the sides, mounted high up to avoid contaminating and disturbing the landing site. Additionally, while JPL had been locked out of the main design competition, both centers had become interested in noises about some type of asteroid rover spacecraft they had heard coming out of Pasadena, being developed for Fobos Together. Despite the growing competition between Ames and Langley, both agreed that a rover would be a very useful addition to their missions, and both contacted JPL inquiring about whether they might be able to have one for not much money. To the surprise of many familiar with NASA’s intragency struggles for power and funding, JPL management was agreeable, and an agreement for JPL to build two “prototypes” for Ames and Langley was quickly hashed out.
By the time JPL started work on its “prototypes,” it was already becoming obvious that cooperation, not just competition, was going to be vital for the future of low-cost planetary exploration. And, as both Ames and Langley began to move from bending paper to bending metal for their spacecraft, that the success--or failure--of Gore’s attempt to bring down the cost of exploration was going to depend on their ability to choose the best time to engage in each.
But I did refrain from posting it!
