Many veteran engineers from NASA are skeptical about the idea that less experienced teams with fewer resources could possibly replicate the space agency's success at developing spacecraft to carry humans — ranging from the Mercury and Gemini capsules to the Apollo command module and the space shuttle.
But the task may be far less daunting than the skeptics think. This is because the "goal posts" in human spaceflight have shifted over the decades, and the required know-how has spread even as the general level of aerospace engineering capabilities has risen. The commercial space shippers of the 2010s will not be recapitulating the research, development and designs of the 1960s.
First of all, the space taxis being created to serve the new policy are being designed for an entirely different mission. Unlike America's previous spaceships, these new taxis will be focused only on delivering passengers from Earth’s surface to an existing space facility and back again. There’s no need for long periods of independent orbital cruising. There’s no need for carrying equipment to be later used for moon flights.
The plan to reshape the Orion spaceship as a standby rescue vehicle for station crews has profound implications for the requirements of the commercial taxi and its cost. This strategy means the taxis won't have to last for six months "parked" in space, like Russia's Soyuz spaceships. The simplification of the taxi’s mission will allow its hardware to be significantly less expensive to build and to validate.
The crucial systems for the taxis have mostly already been built and are available as off-the-shelf technology — which means the spaceships could be much cheaper, much smaller and much more reliable.
Fewer bells and whistles
The NASA vehicles for human spaceflight have been complex because they needed to perform a wide array of complex missions. However, when it comes to building a vehicle aimed at one and only one specific type of mission, a lot of routine equipment becomes superfluous.
Imagine a vehicle designed to dock with a space station within 24 hours. Its maximum emergency flight time would be no more than 48 hours. What kinds of equipment would it need? Here are some suggestions:
All of these items have been critical to the successes of some previous astronaut missions, but if they can be done without, they need to be scrubbed out.
NASA would never build a spacecraft this spartan. But NASA has never designed a spacecraft purely for the space taxi role. NASA has never designed any sort of taxi for use anywhere.
That may explain why the Apollo and Orion vehicles built by NASA for crew transport missions weigh in at the 40,000-pound level and higher, while simpler spacecraft from Russia and China are less than half as massive. Using new structural materials and leaving out fancy extras, some designers suspect that a bare-bones space taxi for four people would more likely weigh in the range of 10,000 pounds, allowing the use of medium-class boosters already in service.
Solving the hard problems
Providing the sophisticiated critical systems for space taxis will involve significant engineering challenges. But here too, the modern equivalents of mail-order catalogs are available to the taxi designers. The two most critical technologies are escape systems for launch and thermal protection for entry. They're not yet in the Edmund Scientific catalog or on eBay, but almost.
These technologies are expensive and time-consuming to develop. Fortunately, the problems associated with their development are already being solved, and those solutions would be available as government-furnished equipment ("GFE," in the contractor term). They would not need to be solved again from scratch.
Orion's launch abort system is scheduled to be flight-tested next month at the White Sands Missile Range in New Mexico. Designed to make the Orion 10 times safer than earlier U.S. spaceships, the tower mounts to the nose of a crew-carrying capsule and hooks into an emergency activation system in that spaceship. The system can also be activated via ground commands. When fired, its 500,000 pounds of thrust pulls the capsule to supersonic escape speed in two seconds.
Lauri Hansen, the systems engineering and integration chief for Constellation at Johnson, recently told Aviation Week how tough it is for any spaceship builder to develop such systems. That’s where she now sees her work bearing fruit: “When I think about what our legacy would be, probably the biggest single thing we could place on the table is an abort capability,” she told AvWeek reporter Marc Carreau.
The system is already being managed by private contractors: Orbital Sciences Corp. is the integrator for the system, and Alliant Techsystems and Aerojet supplied the motors. Funding additional tests and any special interface hardware for different commercial vehicles would be straightforward and relatively inexpensive.
Tougher yet lighter materials
New technologies for reliable and durable heat shields are also just around the corner. The super-secret military spaceplane known as the X-37B will, among other space tasks not disclosed, prove out an entirely new heat shield that will be shared with NASA — and through NASA with all the commercial space taxi builders. The materials are tougher yet lighter, making them ideal for reusable commercial spacecraft.
Air & Space magazine recently described these materials. First, there are silica tiles impregnated with the newest version of “Toughened Uni-Piece Fibrous Insulation” (TUFI), a material already introduced on shuttle flights. This material is resistant to impact and prevents any cracks from spreading further.
The magazine said the leading edge of the X-37B's wings have come in for special treatment. Damage to the wing leading edge during launch is thought to have been what caused the shuttle Columbia's catastrophic breakup in 2003. For this region, the X-37B uses “Toughened Uni-piece Fibrous Reinforced Oxidation-Resistant Composite” (TUFROC, or "tough rock"). It was developed at NASA's Ames Research Center in California to resist the kind of damage suffered by the older reinforced carbon panel panels of the shuttle.
Through a combination of on-hand NASA technology, scrubbing of superfluous systems, and ingenious design with thorough testing, the task of building space taxis seems well within the reach of several different design teams, especially those who hire experienced NASA engineers who are seeking new challenges.
Final piece of ‘space baggage’
There’s probably one more piece of mental "space baggage" that, if disposed of, could make the future space taxis even more affordable. There should be no compromise when it comes to reducing the risk of crew injury or death. But the risks of mission failure should most definitely be re-evaluated under these new circumstances. Failure may sometimes be an option.
It’s a truism that the last few percentage points of mission reliability costs as much as the first big chunk. A 98 percent reliable system probably would cost twice what a 95 percent system costs, and 99.5 percent reliability probably costs twice as much as 98 percent. When national prestige rather than cost is the leading driver, any expense is justified to avoid world embarrassment.
But for a space taxi fleet, or for several independent fleets, supporting a high annual launch rate, the "design driver" is very different. Certainly the aim is to deliver the highest possible crew safety. But the overall system — and the public’s perception of it — should be able to tolerate a small number of mission aborts. These could occur at launch or during rendezvous, or involve an off-course landing or unintentional splashdown.
These missions could be rapidly reflown, and the cost of the makeup flights would easily be absorbed by the lower cost of every other flight. In fact, if there are no mission aborts after several years of operations, the lesson might be that too much was being spent on reliability. That might be the only way that a future space taxi fleet could fall short of the promise of wide-front breakthroughs in human orbital access.