Chair Force Engineer

Monday, May 12, 2008

Two Ways to CRATS

This month, movie fans eagerly anticipate the revival of the beloved Indiana Jones movie franchise from the 80's. But within the halls of NASA, the only 80's movie franchise that's relevant is Back to the Future. In the view of some space policy commentators, the return to capsules and expendable rockets is a step backwards. Of course, to view the return to capsules & expendables as a step backwards implies that shuttle was a step in the right direction, albeit a small step.

Last week, Charles Miller & Jeff Foust wrote about an initiative to create Cheap, Reliable Access to Space, or CRATS for short. In many ways, it appears that any ambitious plans on the part of NASA's manned space program are severely curtailed by our lack of access to CRATS.

Companies like SpaceX, SpaceDev and United Launch Alliance are taking steps towards CRATS with plans for manned, commercial launches on Falcon 9 (with Dragon capsule) or Atlas V (with DreamChaser lifting body.) But expendable rockets are only marginally capable of meeting the requirements of CRATS. The ability to launch on demand is non-existent, and there will always be inherent safety advantages from the reuse of hardware.

There are two ways ahead for developing a truly reusable spacecraft. One relies on the private sector, grows slowly and incrementally, and leverages the lessons learned from the first generation of space tourism. The other would be a Big Government enterprise, occur on a shorter schedule, and leverage lessons learned from the Space Shuttle.

The most lucrative future market in the space business during the next decade will be suborbital space tourism. SpaceShipTwo will lead the way. As prices inevitably drop, demand will increase. There will also be competition amongst spaceship vendors to improve the quality of the space tourism experience. Successors to SpaceShipTwo will literally fly higher and faster, offering space tourists more breathtaking views and longer periods of weightlessness.

During the development of the space tourism market, the industry will learn a lot of lessons about what's required to achieve quick turnaround on a manned spacecraft. There will also be an evolution as vehicles progress from speeds around Mach 3 all the way up to velocities which will tempt aerospace vendors to flirt with the idea of orbital flight.

The NASA-traditional, big-government approach to CRATS is to incrementally build off what currently works, rather than abandoning it to museums (as was shamefully done when Apollo shut down.) The Space Shuttle Main Engine and SRB's are far from perfect, but they do work. Why not wrap an aeroshell and wings around an external tank, mate it to two SRB's, and put a cluster of SSME's on the back end? Such a vehicle would require a lot of political will to develop, but it would probably be on a similar scale to the will required to pull off Ares V. It would also require less changes to the existing infrastructure at the Cape than the current Ares V plan. It could be sold to COngress as a better plan for retaining Shuttle jobs than the current Ares plan.

Along the way, such a "Shuttle II" could be subjected to incremental changes during the spiral development cycle. SSME's could be redesigned for higher reliability (possibly by switching to a simpler, lower-performance gas-generator cycle instead of staged combustion.) The SRB's could be replaced with liquid-fuel boosters. The idea is to build and test incrementally, incorporating lessons learned with each spiral.

"Shuttle II" could survive as a jobs-retention program, but it's really overkill as a tech demonstrator. If we really want an experimental demonstrator to teach us about quick turnarounds and reusability, why not dust off the X-33? The SSME could be substituted for the linear aerospike. If higher velocities are desired, two X-33's could be mated in tandem as a "bi-mese" launcher. The appealing thing about the X-33 idea is that the prototype is still in storage, and there is some support within the Air Force for bringing it back from the grave. If the Air Force kicked in a substantial amount of money to make it happen, I'm sure that NASA would take it.

It will be interesting to see if CRATS is ever achieved during my lifetime, and what approach will eventually win the day. The beauty of the private-sector approach is that the market will grow along with the growth in capabilities, ensuring that we don't end up with an orbital hangar-queen, lacking in meaningful payloads, at the end of the journey.