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RCgothic

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Everything posted by RCgothic

  1. It's easy for shorter rockets to look quick. The same speed is more body-lengths which is how we tend to judge speediness.
  2. I did comment that the mystery frame looked like tension members. That's making more and more sense the more of it they build.
  3. I'm having an off day. Think I misplaced a kg for g somewhere, and 1k cm2 to a m2 instead of 10k cm2. Thanks for the corrections. Think a 1cm/s kick would be more noticeable rather than seriously injurious.
  4. Nice to see Falcon Heavy getting more missions. I think we're overdue a few.
  5. The swept distance over a microsecond at 30km/s is 3cm. The average human is ~500cm² frontal area so you'd sweep out 1.5 litres of stellar corona. As a diffuse plasma it would reasonably be expected to penetrate skin rather than be deflected. The density of the Corona at the edge of the photosphere is ~0.0000002g/cm3. The 1.5 litres contain 0.3g of stellar material, 9kgm/s of momentum, 135kJ of kinetic energy, and approximately 15kJ of thermal energy. This would all be transferred to the unfortunate traveller in addition to the radiative effects other people have outlined. A human is about 20cm thick and weighs 60kg, so the wind-facing 3cm would account for about 9kg. Those 9kg would be kicked backwards at 1m/s and heated by ~4 Kelvin near-instantaneously. It wouldn't be a fun kind of 1m/s either. More like hitting a less-friendly concrete wall. Could come with severe deceleration injuries.
  6. Sure, but in this instance I was speaking purely in terms of propellant delivery to LEO. In every case a means of transferring propellant would be required, but that's a necessary technology for getting to Mars. Full drop tanks would be harder. It'd be easier structurally to put up the tanks as payload and then transfer the residuals from the upper stage.
  7. The vast majority of what will be required for a Mars mission is fuel, so residual props isn't necessarily the wrong way to go. So long as the booster can put up a lot of them on a reasonable timescale for a reasonable cost. That's not SLS by any measure. It might be FH, or Vulcan, or New Glenn though. Even if Starship never works reusably as intended, there's no serious reason not to think it'll be an enormously cheap way of putting up a lot of propellant cheaply and often.
  8. I made no assertion about Falcon Heavy at all in the section you responded to. I said "Some other Booster". It may indeed be the case that Falcon Heavy can't lift more payload to LEO than Falcon 9. That doesn't change the fact that SLS is never assembling a Mars mission. A reasonably worthwhile Mars mission will take over a thousand tons to LEO. SLS can't do that on any reasonable cost or timescale. If no other booster exists that can do that then we're not going until one does.
  9. Yes, that's the thing that annoys me most. Not that it's a badly designed architecture that can't accomplish any mission by itself, but that it shouldn't be as expensive as it is and it could be flying over four times as often for the same money. The opportunity cost is staggering. If any part of SLS/Orion goes to Mars it'll only be because the vast majority of the work was done by some other boosters. It's completely incapable of constructing any practical mothership in either LEO or at Gateway at any reasonable cost or timescale. "SLS /Orion is how we get to Mars" is one of those statements I classify as *lies to investors*. In which case it'd be somewhat competitive to Falcon Heavy, we could build five times as many for the same price, four cargos for every crewed, and the extra launches would cover Orion's weak points. That'd be the kind of SLS I could get along with. Well they have to pretend Gateway is useful for something. Even with full ISRU I'm not convinced fuelling a Mars mission at Gateway (LLO would be better) is worth it compared to assembling in LEO.
  10. SLS / Orion are the least essential bits of Artemis, tbh. Take away the commercial support of Falcon Heavy, Vulcan, Starship or HLS, and people don't walk on the moon period. Take away SLS/Orion and we can still make something work by Earth Orbit Rendezvous, probably for a good deal less money.
  11. Wow, I hope we get lucky and these two don't collide. That's a lot of debris to have in a highly inclined orbit.
  12. Humans are capable of self-motivating, so no syrup pipe for us!
  13. I also think catching starship in a net is nuts. Even with a ridiculously long breaking distance a net that size is not inertialess. An impact at 70+m/s isn't fun for reusability. Lots of TPS on SN15:
  14. The first piece of SN20 has been spotted: This being the first piece of the next major block of starship upgrades beyond the SN15-class of starships and potentially the first piece of a starship to orbit.
  15. On my last project a missed delivery slot for a 30t payload for 150 mile transport cost on the order of $15000. Three times further for $45k sounds about right.
  16. I'm pretty sure this is the sort of thing we could sim these days.
  17. I estimate that GSE tank is ~2000m3, or about half a million gallons.
  18. https://en.m.wikipedia.org/wiki/Impact_depth Newton's Impact depth approximation implies it'd struggle to escape the atmosphere. It has to move through all space occupied by all the mass in its way, which must move faster than it to get out of the way. But by conservation of momentum it can't give more velocity than it starts with to an equal or greater mass without coming to a complete halt. The approximations look reasonable. Blunt body. High velocity. Non-cohesion of the impacted material.
  19. There's about 10 tons of air above every square metre. The plate at 100mm thick (4in) has an area of ~1.25m2 or ~1.2m diameter. It'd therefore need to move between 11t and 1.1t out of the way on its way out of the atmosphere depending on how it tumbled. If it survived it would necessarily be going a lot slower by the time it reached space.
  20. I wonder if the header tank imploded again. Stir the tank, get an implosion, mix methane with oxygen, boom. They said they were taking the helium pressurant away again.
  21. Well, SpaceX's are. AJR's engines on the other hand...
  22. THis is the latest on cost. Not sure what's changed since.
  23. So announced 3-4 months from now means a delay to 5-6 months time. Sept-Oct time. Let's see if that's how it happens.
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