4 thoughts on “Congratulations To Scaled”

  1. I do wish they would overcome their attachment to old seemingly simple but actually complex and problematic technology and switch to a fast turnaround RP-1/LOX engine. They are years past the point when they should have stopped digging, so to speak. The rest of the design is reasonably good and long term economically viable (also subject to incremental improvement), but the hybrid engine is too operationally expensive and problematic – it sets them up to fail.

    With the hybrid engine they are not a serious long term contender – a huge wasted opportunity.

  2. The problem with that is the SS2 airframe is very closely integrated with the nitrous oxide tank. Going to LOX would involve a major structural redesign, likely to take one-two extra years. (Unless they could figure out how to put the insulation inside the tank? But that’s non-trivial also…) Practially speaking, they’re stuck with nitrous.

    Some sort of nitrous/liquid-fuel engine might be possible without major airframe redesign, but the problem there is, that’s not an off-the-shelf engine (that I know of anyway.) So that’s an extra couple of years also.

    The SS2 design team is in a place where, assuming silence actually means engine problems (possibly also assuming the lack of video means the problem is unstable combustion) their best chance of powered flight in less than a year still probably is to keep working the bugs out of the current engine. Any given next tweak could be the one that fixes things. Whenever they finally start having clean full-duration engine runs to brag about, they’re months from powered flight.

  3. Yes, industrial LOX and LN2 both come in stainless steel vacuum-insulated dewars. The dewars weigh too much for flight though – flight LOX tanks tend to be made of aluminum (or occasionally composite, but that’s another discussion) with lightweight insulation on the outside. Boiloff rate is much higher than for dewars, but you can top off the tank right before flight so it’s not an issue for short-duration missions.

    SS2’s oxidizer tank is graphite-epoxy composite, not compatible with cryo temperatures for reusable applications because it cracks with thermal cycling. And they can’t just pop the tank out and replace it with insulated aluminum; the tank is closely integrated into the airframe as a whole, serving as the main engine thrust structure among other things.

    Hence, insulation inside the tank as a possible solution, to protect the actual tank structure from cryo temps. It’s been done before, but it presents considerable manufacturing problems – it’s not a low-risk alternative either.

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