Armadillo Aerospace (and many others, a decade or two ago) showed that rocket engines could be developed and built quickly and cheaply. The cost is in the optimization.
Choosing a hydrogen engine (which only really makes sense for upper stages) also means you need a hydrogen tank... a cryogenic hydrogen tank. They chose to make such a tank with a weird shape that fit the unnecessarily weird shape of their prototype. I think the major cost of getting their craft repaired (or more realistically, having a new one built) was to build a new custom hydrogen tank.
Crazy, when they didn't need anything optimized/complicated for testing launch and landing.
Also wild that they went with an F/A-18 accelerometer/gyro package. The first commercial mass market MEMS accelerometer was introduced in 1991 and was in volume production in 1993. I mean, they had to pick something and the ADXL50 wasn't ready yet (and they would still have had to design a 3-axis solution around it if it were), so I don't blame them for that (expensive) decision.
I do very much blame them for the choice of the RL-10, though. And for going immediately to such a large size -- that's the same thing as saying "we plan on not making any mistakes".
I agree, but still - what could they have used that was not "build your own engine" ? They seemed to have preferred (or maybe were forced to ?) use off the shelf hardware, even if sub-optimal.
The only engines that were not hypergolic & used kerolox were those used on the Atlas rockets or on the Deltas. Not sure if they had the necessary throttling range and other characteristics. I guess now I need to find some sort of a biography from someone working on the DC-X project. :D
As for Armadillo Aerospace - their efforts were admirably and I really enjoyed watching their progress. And they did manage to get a working engine. :)
Choosing a hydrogen engine (which only really makes sense for upper stages) also means you need a hydrogen tank... a cryogenic hydrogen tank. They chose to make such a tank with a weird shape that fit the unnecessarily weird shape of their prototype. I think the major cost of getting their craft repaired (or more realistically, having a new one built) was to build a new custom hydrogen tank.
Crazy, when they didn't need anything optimized/complicated for testing launch and landing.
Also wild that they went with an F/A-18 accelerometer/gyro package. The first commercial mass market MEMS accelerometer was introduced in 1991 and was in volume production in 1993. I mean, they had to pick something and the ADXL50 wasn't ready yet (and they would still have had to design a 3-axis solution around it if it were), so I don't blame them for that (expensive) decision.
https://qringtech.com/TryMe/wp-content/uploads/2014/01/Histo... https://www.analog.com/media/en/technical-documentation/obso...
I do very much blame them for the choice of the RL-10, though. And for going immediately to such a large size -- that's the same thing as saying "we plan on not making any mistakes".