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Everything posted by RCgothic

  1. Formula E is a bit like F1. Accelerations are similar, but the electric cars top out at 170ish mph Vs 230mph for F1, and each driver has two cars and they swap half way through because the batteries can't go full distance.
  2. An expansion ratio of 107:1 (Elon says it could get a little bigger) is not exceptional for a vacuum engine, but it is amazing at sea level. High chamber pressure really helps! RVac knocks the socks off RS-25 (67:1) as a sustainer engine but not a pure vacuum engine like MVac (1:165) or RL10(1:280). There are still trade offs like being able to fire at sea level, fit in the engine bay, and regeneratively cool a nozzle that large. But the number of things this Raptor is great at (if not exceptional) certainly beats every other engine. It seemingly has no weaknesses.
  3. And it wasn't an unsupported test, which helps explain its sea level durability a little, but maybe not entirely:
  4. So the brief is more like: "Design a robot deployable from an HLS lander and we'll pay $55k/kg returned to the lander."?
  5. Am I missing something? $25k per lb is $55k per kg. A reusable falcon nine costs around $50m, so let's be completely optimistic and say a rock-gathering return spacecraft can be done for $50m - $100m total. To turn a profit on that you need to return around 2000kg of rock. F9(r)'s mass to TLI is ~3300kg. That's not returning 2000t of rock. Falcon heavy expendable can send about 20t to TLI, but certainly costs at least $250m inc rock gathering spacecraft. Needs to return over 4.5t of rocks. That's still not happening. Is NASA going to pay for the mission as well as the retur
  6. I'd say SpaceX is likely to continue development whether or not they get NASA funding. Blue might. Dynetics would perhaps struggle.
  7. I take your point, but part of this comes from one of the tweets surrounding the conversation quoted above in which BE-4 was described as "more advanced", ambiguously conflating TRL and sophistication, which is why I went into every metric like I did. Also some of Raptor's design aspirations have legitimately moved, such thrust of up to 3.1MN. The point stands I think, that I can't think of any metric on which BE-4 is better than Raptor.
  8. 18 months ago. BE-4 is a year ahead of Raptor. 18 months later BE-4 is definitely not ahead. In fact I can't think of any metric on which it competes. Engine cycle? Raptor's full flow staged combustion is more advanced. Development? Raptor is further along. Prototypes? Raptor has at least 40. Testing? Raptor has flown actual flight articles. ISP? Raptor is ahead. Thrust? Raptor is already topping BE-4's 2.4MN. Cost? Raptor is certainly a lot cheaper. TWR? Raptor is on course for better than Merlin. Size? Raptor fits all the abo
  9. Hang on, it was JRTI on station for this mission. How much more upgraded can the thrusters get?!
  10. Briefly thought it would be cool to see them practice the manoeuvre with old F9s, but on further thought falcon's probably not capable of 1) entering the right attitude, 2) relighting engines in that attitude, and 3) surviving hypersonic sideways flight. Also I'm quite attached to the Falcon flight leaders, I don't want to see them lithobrake!
  11. Tim Dodd, The Everyday Astronaut, posted this earlier. One error that's been caught already is that there are parts for 7SRBs, not 35.
  12. Here's the thing. Even if Starship completely fails to survive EDL and they can't fix it. If they never get refuelling in orbit to work. If Superheavy never sticks a single landing. Then you can still retool the system as a conventional expendable rocket with ~250t payload to LEO and IDK, a 12m payload fairing, and all 34 engines *combined* will cost about half as much as a single RS25. Even if Starship/Superheavy is a complete abject failure, it still renders SLS totally obsolete.
  13. SN9 and 10 are starting to get sleeved. I think some of SN9's sleeved domes may have been mated to some additional rings but I'm not sure. SN 11 is still just bits.
  14. If something goes wrong with SN8... No big deal. SNs 9,10 and 11 are waiting. If something goes wrong with the green run... No Artemis One.
  15. STS could put what, 110t of mass in LEO, 78t of which being orbiter? If SLS could put 10m diameter payloads of up to 110t into LEO 3-9 times a year at roughly the same cost as the space shuttle, then that would be a useful capability no matter what it was used for, even in the face of new commercial competition. Sometimes that 110t could be a departure stage for BLEO missions. Useful! I think it would save a lot of money in assurance if crew never had to go up on it, but even so it could still work. But I don't understand how you start with shuttle, add an engine, and get less mass t
  16. Sure, but large diameters are not essential for any mission other than telescopes, and as you say the large diameter capability is on the way.
  17. Berger's not wrong. SLS/Orion is stupidly overpriced. If it all worked perfectly for launch tomorrow it still couldn't put boots on regolith. It can't co-manifest a lander with Orion and the lander isn't ready anyway. For the price of the SRBs and RS25s alone you can get ten fully expendable Falcon Heavy flights or 20-30 Falcon 9s. You can build a better moon mission around a fraction of that lift capacity with a little in orbit assembly. The only reason they haven't is because those boosters came along after Congress made its mind up. With even greater commercial heavy lift com
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