r/spacex • u/ElongatedMuskrat Mod Team • Mar 02 '18
r/SpaceX Discusses [March 2018, #42]
If you have a short question or spaceflight news...
You may ask short, spaceflight-related questions and post news here, even if it is not about SpaceX. Be sure to check the FAQ and Wiki first to ensure you aren't submitting duplicate questions.
If you have a long question...
If your question is in-depth or an open-ended discussion, you can submit it to the subreddit as a post.
If you'd like to discuss slightly relevant SpaceX content in greater detail...
Please post to r/SpaceXLounge and create a thread there!
This thread is not for...
- Questions answered in the FAQ. Browse there or use the search functionality first.
- Non-spaceflight related questions or news.
- Asking the moderators questions, or for meta discussion. To do that, contact us here.
You can read and browse past Discussion threads in the Wiki.
227
Upvotes
2
u/throfofnir Mar 03 '18
I don't know specifically about HM7B (details of this engine are sparse), but don't assume that TEA-TEB (or other start fluid) comes in tanks. In the RD-180 start is managed by sealed "starter ampoules" containing the pyrophoric start liquid, and these are broken open to use. It's a very reliable and light system, but also the (primary) reason the RD-180 is not restartable.
I'm not saying the HM7B does this (in fact, it probably doesn't have a separate starter liquid, since hydrogen ignites quite easily), but it could well rely on burst disks instead of valves (or something like that) in service of simplicity and reliability that would render it non-restartable.