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Everything posted by RCgothic

  1. Given all its design compromises, its impressive that STS even worked in the first place. Manned launches have no business being on a rocket with no abort modes. This was entirely foreseeable and my big beef with the shuttle. At some point somewhere someone went "we don't need those" and that's unacceptable when an alternative design with capsule on top has no issues. Possibly rapid reusability wasn't possible without compromising on the abort modes, but in that case the goal shouldn't have been pursued until it could be done in a way that preserved the abort modes, and yes, I apply this reservation to BFR as well. The second fundamental problem with shuttle is cargo and crew on the same vehicle. You just don't have to risk a crew and pay for crew rating to put up a comsat. If what you need to put up is a crew, there's no reason why you can't rendezvous with whatever they need to be doing in orbit. The only ability unique to shuttle was significant downmass, and there's no reason a low-g return module could not be designed and deployed at a fraction of the price of a couple of shuttle missions had that ability ever been really needed. The third big problem is that shuttle became a pork project. It went on so long subcontractors and senators feel entitled to the work shuttle provided. The program has never really been allowed to end despite not flying anymore, and that stops NASA from doing any better in subsequent designs. Finally, a replacement should have been designed in parallel to shuttle operation. That budget for doing so was not available was a congressional issue, not an issue with NASA. On a side note (because not shuttle specific) the comparison of what happened to Challenger to wind shear detectors at airports. It's not the same thing. The engineers knew the o-ring wasn't good for those temperatures and said so. The risk was known at the time and they were ignored, it's not an unknown phenomena suddenly tripping us up. The failure could happen to any craft abused beyond its limits. If you want all-weather launch capability it needs to be designed in from the start. That shuttle didn't have it isn't really shuttle's fault as it's lack of a design requirement.
  2. I mean there may be volatility issues with sealants or materials or such that you'd only discover in a true vacuum test. For pressure vessel integrity I completely agree that 3bar should be good enough.
  3. In terms of pressure differential I'm sure three atmospheres would be fine, but there may be other factors that can only be tested in a near vacuum environment.
  4. An asparagus has leaves overlapping in a spiral pattern. For an asparagus staged rocket with a large number of stages, the stages usual end of dropping off in a spiral pattern.
  5. Honestly I doubt there's an analytic solution for Pn engines. I envisage a program where you step through every possible combination of engine thrusts in 10% increments for combinations of values close to zero on all but the 1 degree of freedom you're interested in. Then iterate at a finer resolution around those values. Repeat for each degree of freedom. It's a brute force approach but should give you a solution of there is one. May miss 'spiky' solutions where equilibrium is reached very quickly from an unlikely combination.
  6. Not an easy problem! You need to work out what combination of engine thrusts provides rotational equilibrium. As others have mentioned there may be more than one unique solution. Then you either want the axis (solution) in which you get maximum thrust or maximum ISP depending on whether or not you are fuel limited or time limited. Over any reasonable time period the answer will always be to first rotate the axis of maximum engine thrust or maximum isp onto your custom vector.
  7. I have no doubt we could manage it with current tech. The problem is budgets and timescales. On current budget the timescale is not getting any closer to the present. On budget max you'd still need to design build and test the interplanetary hardware before the next Mars window, as SLS is not nearly sufficient. That's not happening, as there's too much to do. Even the window for a first interplanetary unmanned test after that is only 2020, which is really pushing it. Finally even if that goes perfectly you need to wait again for the next window in 2022. That's April 2023 manned arrival at Mars at earliest.
  8. Yes. Falcon 9 almost gets away with it because second stage does most of the work of getting to orbital velocity. Falcon Heavy first stages lift more payload to a little faster than Falcon 9, but the 2nd stage really struggles. Half as much DV or less.
  9. From what I've heard on Reddit, it was a ridiculously close call and insiders say they're not going to release it for PR reasons. Firstly, look at the scorch trail across the barge. Also the last frame shows spray being kicked up way off the mark. The rocket clearly pulled some crazy last minute manoeuvres. Secondly, insiders describe the booster balancing on one leg and nearly toppling. There is also a reference to CRS6 and the little thruster that couldn't. Apparently this time it could. So the video sounds ridiculously awesome, but don't hold out any hope for a release!
  10. New Glenn is projected at 45t to LEO and 16t to GTO reusable. It will never fly expendable. Falcon Heavy is projected at 8t to GTO reusable. Payload to LEO reusable is speculative. To match New Glenn 16t to GTO at least the center booster need to be expended (possibility). Falcon Heavy has the potential to beat New Glenn flying expendable, but that's not really comparing like to like.
  11. If they can stick the landing with accuracy, maybe they'll be able to build a freshwater /de-ionised landing pool?
  12. Of course the poor dwell time of the hydrogen EUS means you won't be assembling anything in LEO, which limits SLS to small high energy payloads. It's basically useless for anything else.
  13. I think there's also a slight plane change manoeuvre required, which is cheaper at higher apoapsis.
  14. Can we back calculate what the maximum payload to the minimum GTO is and compare it to Spacex's stated values?
  15. Three: Even copper corrodes over cosmologically significant time periods (millions of years). Just because something is frozen does not mean it will remain intact and functional ready to be defrosted. I've some professional experience with trying to keep things protected over mere geologically significant time (tens of thousands of years) and I'd say the only hopes lie at a significant fraction of the speed of light. As we can't use the entire mass of the solar system as reaction material you are going to have to find a very large black hole with a shallow gravity well in a quiet neighbourhood (the less the black hole is consuming the lower the radiation/bombardment hazard) and slingshot very close to the event horizon. Of course, finding and travelling to such a black hole will take a cosmologically significant time period, so basically no. Not even a digitally stored simulation of a person's consciousness could be kept over that sort of time period.
  16. Thank you for clarifying.
  17. How is 'most reliable' and 'heavy' defined in that analysis? As far as I'm aware Saturn 1B had 100% success.
  18. Lift is a function of both wing area and velocity. A Cessna needs to go supersonic. Something built like a U2 would not.
  19. Still doesn't make sense. Orion is massively over engineered for trips to LEO which for the foreseeable is the most sensible place to assemble the mars mothership. It's rated for lunar returns. In that respect it's well suited for DSG, but DSG is just make-work. DSG isn't a sensible assembly location because it takes more propellant to send assembly materials to DSG and then to mars than it does to just send straight to mars from LEO. There are still no serious plans to revisit the lunar surface. As far as Martian returns go, the Orion is a heavy piece of hardware you don't want to take with you. On return the mothership is expensive enough that you're going to brake it into LEO rather than lose it and re-enter direct from Mars in an Orion whilst losing the rest of the ship.
  20. Orion isn't designed to go to Mars. It has nowhere near the required habitable volume for that duration. Neither is SLS - it can't loft nearly enough propellant for a crewed mission to mars and the hydrogen upper stage doesn't have the endurance for on-orbit assembly at the proposed launch cadence. Nasa does not yet have a serious plan to get there and the hardware required is currently all vapourware.
  21. Also, though it didn't have any loss of craft, Saturn and Apollo had several very near misses. If it had kept flying there'd probably have been a tragedy. It was an amazing machine, but let's not pretend it was perfect. A new booster would have better payload fraction and better safety margins for lower cost than resurrecting the dead. Not that SLS is the right approach either.
  22. I'm up to bag 5/6. Stage IC nearly complete! It's nice and solid, but I'm a little disappointed the interstage ring remains attached to SIC. I'm already pondering if I can alter it to be a separate piece. Just the F1s let to do! Also noticed looking ahead that for the command module you have to swap between the Boost Protective Cover version and the one without. Guess they don't have a hollow piece to go over the top of a cone piece!
  23. Presumably the ICPS does make a difference for less than full payloads to beyond LEO. But that is ridiculous. As if we needed more reason to diss the SLS.
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