HOUSTON - As a retired rocket scientist and avid space historian and strategist, I’ve been watching the debate over NASA's future in human spaceflight with great interest. I've been quite impressed by the questions coming from the independent panel charged with laying out the options for that future.
Now that the panel's members have released a report summarizing the options available to the White House, I have even more respect for their analysis.
Next, it's going to be up to the Obama administration, and those deliberations will follow a logic I'm not familiar with. None of us really knows what criteria the White House will use to select NASA's future course, or how policymakers will mix and match among the options. In all my years of experience observing the Space Age, working within the heart of it, and writing and speaking widely about it, I've found that expecting rationality in the debate over space policy is often a folly that ends in tears.
I do want to make one plea, however. My own contribution to the national debate is going to be a defense of the much-maligned “look but don’t touch” option — what the panel calls "Flexible Path." I think it deserves more respect than it’s been getting, and I'd be content to see it emerge from the process. But I'm not getting my hopes up (see "folly," above).
I deeply respect the parade of "planetary partisans" who have argued for the moon next, or Mars next, or an asteroid next. Many are old, old friends of mine and I wish them all well. But whenever the answer comes before the logic, the argumentation is bound to be a little suspect.
So, suppose a strategy emerges that does not call for big-world surface footsteps anytime soon. Imagine astronauts flying up to another world, but not immediately descending down onto its surface.
I think there's a lot of new technology that's become available since Apollo that could exploit this strategy, for exciting missions that would mark a breakout from half-century-old mission concepts. We have to be careful to give it a fair shake. This changed course could well be hopeful, imaginative, inspirational — and affordable.
Attitude adjustments required
First of all, in this scenario, the international space station would be continued, with research expanded to the technologies and life sciences issues associated with very long space missions — a year, maybe two, or more. To date, NASA’s experts in the life sciences have been uninterested, even contemptuous, of the idea of flying people longer than six months. Some attitude adjustments would be required.
Innovation could be re-funded. The station would also be the test range for promising new inventions that can shorten planetary trip time from years to months — in particular, the VASIMR plasma engine developed by astronaut-physicist Franklin Chang-Diaz, a good buddy (and former crewmate) of new NASA Administrator Charlie Bolden.
NASA has already approved plans to fly a prototype VASIMR system (a.k.a. "Chang Drive") on the space station, but it won't be ready until after the end of the shuttle program, so as of now it doesn't have a ride. That will need to be fixed.
If the device works as hoped — and Chang-Diaz has been testing larger and larger versions for 20 years — it could bring a piloted spaceship to Mars in two months instead of 10, with the same speed on the return leg. But that's getting ahead of my essay. I’ll return to the Chang Drive later.
NASA has begun serious studies about privately-owned "space taxis," a good idea. Commercializing human transportation into low Earth orbit and back down to Earth would free NASA to optimize its next spaceship — the Orion — for deep space missions. That's a good plan. To get to the space station and other destinations near Earth, NASA can buy tickets on stripped-down taxis that will be a lot cheaper.
Ever since Apollo, NASA’s “people-mover” operation has relied on vehicles with capacities far in excess of what's needed to send spacefliers into Earth orbit and back. Some of the taxi design suggestions are astonishingly — even unbelievably — lightweight compared with what was used for Apollo orbital missions, let alone shuttle missions. I look forward to seeing better ideas along these lines.
To the moon and beyond
Looking beyond low Earth orbit, the next-generation Orion spaceship, coupled with a large Saturn V-style booster, could fly out to higher orbits, to the region of the moon, to low orbits around the moon, and beyond the moon to a variety of gravitational balance points.
One particularly interesting point is Sun-Earth-L2, a million miles "down sun" from Earth, deep in interplanetary space. Unmanned spacecraft are being parked there — and someday they could use servicing, refurbishment and upgrading (note to NASA: equip those probes with grapple fixtures!). Anyone looking back toward Earth would see it backlit by the sun, a perspective that could provide new information about our planet's atmosphere. The environment at L2 is beyond all terrestrial influences — it is genuine "interplanetary space."
Closer to home, the moon should not be ignored. If Orion were to orbit the moon with with its astronaut crew, it needn't be a mere repeat of Apollo 8's flyaround in 1968. Lunar orbit could serve as a region for special operations conducted jointly with robotic systems on the lunar surface. There are places of high interest on the moon that are blocked from view from Earth by mountain ranges and other interference. Astronauts in lunar orbit could operate surface robots by remote control, looking for ice layers in polar craters.
What really intrigues me is that the moon is the perfect place to test out a revolutionary space transportation system — the "skyhook" or space elevator system. The concept has been around for a century: Essentially, just lower a rope from space to the ground, and use that to pull your payload into orbit.
Making the concept a reality in Earth orbit would be far beyond any credible near-term human capability. Not so at the moon. Its lower gravity and lack of atmosphere provide the perfect setting (and the perfect rationale) for a skyhook system that slowly spins as it orbits the moon, dipping its end near or onto the surface every two hours. The tether would have to be heavy, but it is well within the range of plausible space technology.
A "practical" concept for a lunar space elevator was described in Omni magazine by Bob Forward and Hans Moravec in 1981. Moravec expanded upon the idea in 1986, saying the skyhook system would offer "a fine alternative to rockets for getting supplies and personnel to and from the lunar surface."
Such a system could be tested on a small scale at first, and then ramped up incrementally. That's the beauty of this Flexible Path approach: Each step in capabilities leads to the next step within reasonable reach. Giant leaps into the unknown are not called for. Decades-long projects aren't needed. Each new goal is well within the office term of the president who endorses it.
Orion spacecraft (perhaps, as proposed for safety, in pairs) can venture farther from Earth, eventually paying visits to passing asteroids. Accessible asteroid orbits tend to have very long synodic ("repeat opportunity") periods, so there's no time to launch a robotic probe and operate it for a few years before a crew arrives.
It would make sense to dispatch a smaller probe that gets to the asteroid a few weeks before the humans do, to map it and later relay communications to surface operations both human and robotic.
Missions to asteroids could address three fundamental human motivations: curiosity, greed and fear. Scientifically, they are of tremendous value as records of the solar system's history. Materially, they may contain resources (water more valuable than metals) that could be economically exploited for space activities. And in practical terms, knowing how rigid asteroids are may be a matter of life and death someday, when one of them has to be nudged off a dangerous Earth-approaching path.
On to Mars?
The next step could be to send astronauts and robotic supply ships toward Mars, perhaps using high-efficiency ion engines or plasma engines related to the Chang Drive. The initial voyages would have the astronauts stop short of an actual Martian landing. However, there should be no frustration involved here — the mission will be challenging and rewarding enough.
Mars has two very convenient "asteroids" right next door, its moons Phobos and Deimos. They would provide radiation and thermal shielding, material support (perhaps water) and a base of operations for human scientists to run robots in real time on the Martian surface. Beyond Earth, these locations may be the safest place for long-term stays anywhere else in the inner solar system.
Here, the presence of humans near Mars shows its value. With no radio signal travel time, remote operators could drive the rovers and run the sampling equipment in essentially real time. They could control fleets of small and large robots on the surface.
The two Mars rovers currently in operation, Spirit and Opportunity, are mighty impressive. But even the rover team's chief scientist, Steven Squyres, has said that all their science and sampling and snooping around over the past five years at Mars could have been accomplished by a human field geologist in a week. Humans on Mars could move and decide a hundred times faster. But humans near Mars, combined with robots on Mars, offers the best of both worlds: safe access for the robots, plus fast human control from a few thousand miles away.
Surface samples could be rocketed up from the robot fleet on small, simple boosters and retrieved by scout ships sent out from bases on the Martian moons. Eventually, people could descend to the Martian surface. That part is easy since Mars allows air braking. Surface-to-orbit taxis, perhaps modeled after the stripped-down high-efficiency vehicles developed commercially here on Earth over the next few years, would follow. And at some point, with experience from operating at the moon, a Mars-based rotating skyhook system could supplement, or entirely replace, rocket transportation up from the surface.
Imaginary missions ... for now
These are all still imaginary missions. But here's the bottom line: by not getting trapped into replaying old strategies with admittedly better (but operationally unchanged) hardware, new paths made possible by more capable technologies and more informed imaginations could be much more attractive.
The "look but don't touch" option could become "reach out and grab" sooner than any other option — even the options that call for a lot more spending. If such a choice is seriously being considered, we should be careful to treat it with respect and hope, and not instinctively take the side of the moonies and the Marsies and the other destination-driven partisans who have been stepping up to the microphones lately.
It makes so much sense it's almost scary. It's so rational that its political prospects must be slim. So let's not strangle it in the crib.