> "my guess is that it's an expander cycle" It could simply be pressure-fed. No turbopump at all—just a helium tank. You have a preference for assuming sophis

> "my guess is that it's an expander cycle" It could simply be pressure-fed. No turbopump at all—just a helium tank. You have a preference for assuming sophistication, but this is a one-off inexpensive test article with trivial performance needs. My guess is that they'd made the simplest engineering choices possible at every turn.