ment18

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About ment18

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    Spacecraft Engineer in Training

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  1. Ill just leave this here: https://en.wikipedia.org/wiki/Project_West_Ford There are currently several hundred million tiny needles in a high polar orbit, and they have been there since the beginning of space travel.
  2. Both Dragon and Orion have enormous dry masses which mean any lander derived from then would have to be extremely large.
  3. Where is the lunar lander? I think its going to take a lot longer than 5 years to develop a lunar lander, and as far as I know one hasn't even been selected. They would have to do it faster than Apollo, and current NASA/Contractors have not been able to meet much slower deadlines. I watched the video, and this whole thing looks extremely fishy, the lander isn't even mentioned when it is probably the hardest part of the whole mission, so it looks just looks like political messing around. They haven't even seriously designed the lander, and expect to land in a short period of time. The only organization developing a manned moon lander right now is SpaceX, and their project would have to go very well for 5 year landing to happen. Blue Origin might be able to, but they are very slow, like NASA/Boeing, and don't have any experience with orbit, life support, or any of the myriad of other things required to make a manned lunar lander.
  4. Higher TWR can decrease gravity losses quite significantly, decreasing deltaV to orbit so more payload.
  5. Ejecting an entire capsule doesn't make sense, it requires changing the outer shape of the Spaceship to accommodate it, and it will never be able to be even close to off the shelf, you can't just throw a Dragon 2 onto a rocket and expect it to work. Honestly, LES doesn't matter for Spaceship because its reliability is unprecedented. We've never been able to fly the exact same vehicle (both booster and spaceship) five times a month, so you can prove the system works just by flying it ten times. Failures are not random, they happen for reasons and a lot of those reason are manufacturing mistakes and failures that only happen in extreme situations. Both of these are heavily mitigated by flying the same rocket many, many times. By the time people are put in the Spaceship, the system will have flown hundreds of successful missions, making the cost of a LES completely pointless. At some point, adding a LES is just increasing the number of parts that can fail catastrophically. The Spaceship will be highly redundant and highly tested, LES is just a bandaid to the real problem.
  6. By not having COPVs. Shooting regular tanks simply causes fuel to slowly leak out and boil off, nothing catastrophic. They intentionally did this to safe vehicles in the past. If you are talking about sniping passengers themselves, not sure anything reasonable can be done, for any vehicle.
  7. They scrubbed at 30s. They waited until then to see if the upper winds would improve enough to fly.
  8. My guess is that the booster is still composite bc they can check up on it after every flight and it is in a much less severe heating environment, while the spaceship is titanium or some new alloy. The spaceship needs to be much better proven than the booster because it has much longer missions and is more important to cree safety. By still doing the composite booster they gain experience allowing future spaceships to be made in composites, and the dry mass of the booster still matters a lot because it does RTLS, which costs several km/s of dv.
  9. It appears that the core stage of SLS is way overweight. The core stage is pretty close in size to the ET, which was about 26.5t empty. Each RS-25 is about 3.5t, so the theoretical attach 4 RS-25s to the ET should weight around 40.5t. However, the SLS core stage weighs 85t, which seems quite ridiculous to me, even accounting for all the extra structure you would need. Also, the throw weight of shuttle include the SSMEs, and SLS does not, which accounts for some of the mass difference. It doesn't matter if BFR is terribly managed because it is an order of magnitude cheaper and unquantifiably more capable. SpaceX literally can't afford to be as bad as SLS. We know from Falcon 9 that SpaceX is far more money efficient than NASA/Boeing b/c it took them $400 million to do a project NASA expected to cost $4 billion. Elon Musk is behind his schedule and exceeds his cost estimations, but this is disingenuous b/c his schedules are at least 3x more aggressive then anyone else's and his cost estimations are at-least 10x more smaller than anyone else's. Even if Elon does 50% worse than he plans, he still does 2x better than anyone else in the aerospace industry. If you can actually meet your cost and time plans, than you aren't working at your full potential, your plans aren't challenging enough. The mistakes being made by Boeing are similar in magnitude to the entire SpaceX Falcon 9 Project. If you like space travel, why go against SpaceX. They are not hurting anyone unless you think SLS is so garbage that it risks cancellation, which basically says you think SLS is worse then BFR. If SLS is any good, BFR is not a threat so you should want BFR to succeed because it never hurts to have more rockets and it might make space travel massively better.
  10. does that require a metal surface and no air to seal?
  11. http://www.pulse-jets.com/phpbb3/viewtopic.php?t=2701 -- Pulse Jet Tube Temperature >800C https://www.lifewire.com/specs-on-3d-printing-materials-2232 -- ABS Melting Point: 240C Its gonna require a massive performance hit to make up for that disparity, physics of engine might not even allow it because the air flow rate it based on the power of the engine.
  12. I think the temperatures involved mean the plastic is useless, easily liquified far before you get any performance. It needs to be easy to melt to print, unless you have a special printer. I think joining metal components is really the only option. Valves or no?
  13. Its probably easier to connect metal piping together than trying to use plastic, though I'm not familiar with how well shaped pulsejets need to be. How much in the way of tools do you have access to?
  14. nope, hes still ceo, just not board chairman for 3 years
  15. A couple of other points: Musk talked about how many easy manned missions would fly at lower gees, reducing payload for those missions, but tankers onviously go all out. Additionally, BFRs minimum size might be controlled by the propellant plant. I'd want the first plant just to be bolted into a BFR and pretty work light since you have to do everything robitically, just plug in solar, open vents, and add water. This decrease in mass suggests that the factory is more volume limited than mass. I also really like the external cargo bays for their ease of loading in space. For cargo missions, BFS has way more performance than it needs, and the external racks could be loaded up with high density stuff once in space more easily than the internal cargo bay. They could probably pack over 100t of metal 3D printer material into them.