Experts on the Internet
A lot of internet discussion is ignorant speculation, rumor spreading, ranting and flaming. But that’s not all. The freedom and self-organizing nature of enables massive diversity. Newsgroups, mailing lists, IRC, forums, Twitter – and sometimes there’s something there.
Michael Tobis comments on his experience of reading about the Iranian riots on Twitter – way before anything was said in the printing press. Being his usual self, it acts as a motivation for a longer article about the resignation of reporting on important issues (global warming changing earth significantly being Michael’s issue because of his expertise in that).
I’ve long been saying related things in relation to space issues. Now, the traditional media defends its views and sheepish forwarding of NASA public facade material as the right way. Maybe some examples are necessary. The aerospace developments of national agencies are full of failures. All ventures have failures. It’s just that aerospace has so few successes – especially rocketry.
What if Nasaspaceflight.com had existed during X-33? NASP is moot here since it was a secretive military project – hence no insight possible there.
Would X-33:s failures and their reasons have been predicted much earlier? Ares I and V had their critics from before day one. Technical critics. Budgetary. Industrial ones.
What is important and makes things different from mere ranting, or “armchair generals”, is that the NASA and ULA engineers provide, on their free time, insight into engineering matters. Instead of the public affairs that the rest of the media reports on. They have a passion for what they do and want to succeed and advance. If they see hopeless technical incompetence at the top level, they will voice their objections – it is practically their duty as citizens.
X-33 – Marching Towards Certain Failure
X-33:s first failure was trying to use very unproven technology (composite multi-lobed cryogenic tanks) in a billion dollar magnitude program. The technology could have easily been proven on a much smaller scale, very cheaply and fast, before starting the whole X-33 project. Competent engineers should have seen that one as a real high risk with easy reduction possibilities. You don’t risk billions just for fun, if you can easily avoid it! You risk it for politics though.
The table above is from NASA’s tank report (pdf in references), with tests done on tank samples done after the failure, revealing the gross inadequacy of the material for the intended purpose
If, on the other hand, the composite tank was seen as a high risk but not necessary technology for reaching X-33:s goals, then X-33 should have proceeded with the metal tank. In other words, if the composite tank was an optional “nice to have” component. But NASA:s Ivan Bekey testified otherwise – that X-33 had no use without the carbon fiber tank.
All around the X-33 seemed quite big and hugely ambitious on multiple fronts for an experimental vehicle anyway. What were the other objectives besides composite tanks? Could they have been tested in a faster and less expensive vehicle? The metal TPS comes to mind as one. Did it have even the inadequate bench background of the tank? There were military programs from the fifties to the eighties that had developed such things in labs – maybe there was something there.
What about the lifting body shape? The successing Venturestar kept changing shape constantly in simulations and grew big wings. It could very well be that Lockheed Martin and NASA simply didn’t know what they were doing, on any level really, and should not have started building X-33 in the first place. The knowledge base was not at the level to justify going that far yet. The close to existing J-2 derived aerospike engine was perhaps the biggest justification for the size and shape of X-33. But the potential reward of finally getting an aerospike engine flight tested just made the fall that much heavier – the large vehicle necessitated by this turned out to be unworkable. A failure on a lesser scale would not have been as hard. Close to ten years later, no aerospike has yet flown. There have been spike nozzles in hybrids and solids but no aerospikes, where the physical spike is cut off and replaced by a gas jet.
What should have been done to enable the X-33 building?
- Bench tests of composite tanks (basic, room temp, progressing to multi-lobe, cryogenic). Test cryopumping as well (this has been done somewhat since).
- Possibly aerodynamic tests with a much smaller vehicle (or generations) as a glider, first released from a helicopter, then an airplane and finally with a sounding rocket. Alternatively with conventional engines. Possibly horizontal takeoff to reduce test costs.
- Aerospike engine small scale tests. Perhaps contract a smaller company for that, like Armadillo and XCOR have done tests cheaply for NASA methane engines.
If any of these solutions proved unfeasible, then no reason to build the Lockeed style X-33.
Rockwell had a shuttle shaped cylindrical tank vehicle with wings, which seemed pretty simple on the outside. McD had the DC-X growth model. At least both had some heritage in working hardware. There is very little engineering information available about the competitors so if anyone wants to help, drop me a note. Would they have succeeded?
Probably both would have failed as well, in the role of traditional X vehicles of developing new capabilities, mainly because of being too large. Both of the other potential X-33:s would have had a composite hydrogen tank as well (though possibly axisymmetric, even conical or cylindrical), so they could have had similar failure possibilities, though perhaps they would have had a different (sensible) development approach. As is evident from lab tests in the references, cryogenics and composites are hard to fit together.
The Shuttle thermal protection system is notoriously work intensive, and as far as I know, the Rockwell proposal had quite similar tiles in its proposal. On the other hand, surface loading could have been less since the vehicle had its own tanks and high mass ratio. Also the SSME:s are very work intensive when reused. It was partly more of a rehash of existing technologies, which would perhaps have had moderate chance of success. If it worked, maybe one could try different technologies in it, if it was cheap to fly and could do incremental envelope expansion, while still having high enough performance to really stress test things like TPS or vacuum test less maintenance intensive engines. Heat loads on the composite structure would have been an interesting problem area as well.
McD’s precursor for their X-33 design, the small flying DC-XA program was cut prematurely (after having survived agency changes and funding problems) after a crash from a trivial easily avoidable failure, an unsecured hose. It could have made sense to do DC-XA again, to try the high speed properties, flying at different angles of attack and test the turnaround maneuver that it should perform after re-entry for landing. It would also have made sense to keep in the DC-XA scale and try lots of other solutions in the same vehicle (or fleet). It’s cheaper to test when at small scale. Only when the low capabilities of the vehicle would have been exhausted and good enough solutions found, would it have made sense to move to a bigger vehicle.
All in all, space is no different from other fields, that rationality is the most effective way to reach sustained progress. It is obvious to any engineer worth their salt that one should retire as much risk as possible, as cheaply and as fast as possible before moving to the big bucks and long development time game.
Sadly, aerospace seems like a hopelessly irrational field in this regard. There are historical reasons for that attitude. Crash programs like Apollo or military ones have left their mark too deep – the field is unable to grow to a rational mature one. It is evident when looking at NASA’s troubled history with manned spaceflight. Since Mercury, Gemini and Apollo, it has not been able to build much incremental progress. STS was a partial success in capability – but it has stifled progress. Everything must always be started over, and at giant scale – making the unavoidable multiple tries very costly, both in time and money, and even utterly shameful in case of failures. A gigaprogram with failure as no option is a recipe, not for sustained progress, but for either a great disaster, or stagnation. A gigaprogram with failure inevitable is waste incredible.
So, the media of today should examine the world in such a perspective. Simplistic “against NASA / for NASA” analysis serves no one. There have been such incredibly farces lately that I’ve had to double check I wasn’t reading the Onion.
I speak for many, when I say, we don’t want delusional Programs, we want rational Progress!
1 Final Report of the X-33 Liquid Hydrogen Tank Test Investigation Team, NASA Marshall
2 Cryopumping in Cryogenic insulations for a Reusable Launch Vehicle, Johnson et al., NASA Langley
3 Proceedings of the RAND Project AIR FORCE Workshop on Transatmospheric Vehicles, Chapter 3: Design Option and Issues, containing X-33 general overview and info about the competitors, Gonzales et al, RAND Corporation