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About Silavite

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    Mass, Momentum, and Energy Conservation

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  1. I'm not sure that stability is an issue. As long as the time constant for a perturbation away from the velocity vector isn't *too* quick, the flight controller in concert with TVC should be able to keep the vehicle pointed the right way. I would wager that most launch vehicles today are statically unstable.
  2. The idea of a BE-4 modified for hydrolox has some precedent in the LR87, since it was originally designed for kerolox and then was made to use hydrolox and storables in separate variants. That said, the LR87 used a relatively simple gas generator cycle as opposed of the BE-4's oxidizer rich staged combustion cycle. In addition, most hydrolox staged combustion engines (save for perhaps the RD-701) use fuel rich staged combustion. Perhaps it would be possible to stick with the oxidizer rich cycle, but modifying a staged combustion engine to burn different fuel seems (to my untrained eye) li
  3. If I'm understanding the argument correctly: There have been plenty of reentry vehicles, yet none are cylindrical. The cylinder would have been used it were a viable shape. The cylinder hasn't been used historically, ergo it is likely unsound. I think that arguing from the perspective of historical trends isn't necessarily sound in this case. I would argue that capsules have been predominant due to their stability without active control surfaces (only a CG shift and RCS are necessary). Among reentry vehicles with active control surfaces, all thus far have utilized lift to
  4. True, though STS-1 did have a bit of a close call during reentry due to issues with real gas modeling not matching the actual dynamics of reentry.
  5. I believe that the cylinder would have less drag, but Starship's mass/area at reentry is more or less comparable with the STS. Some quick and dirty drawing with MS Paint gives an area of 370 m2 of the STS' underside, and a very crude estimate of its reentry mass (from subtracting LEO payload from MTOW on Wikipedia) would be 86 tonnes, which gives a mass/area of 232 kg/m2. I think that the projected dry mass for Starship right now is 130(?) tonnes, let's say 150 tonnes at reentry. Starship is 9 m in diameter and 50 m in length, but the nose cone has taper, so lets say that the projected area is
  6. For reference on frozen orbits. The ~86° one would probably be most convenient for the polar activities of Artemis.
  7. If this is the first controlled flight on Mars, then I take it that EDL was done via a wing and a prayer.
  8. This thread from NSF gives a partial answer; Orion is just big.
  9. I hate to burst your bubble, but there's already a well-established thread for Orion & SLS.
  10. This is something of an oddly-specific request, but here goes. Would anybody happen to have (and be willing to share) some thermodynamic tables? The substance in question is ideal gas combustion products of air and a hydrocarbon fuel (I believe that it would be something like jet A-1). The tables which my propulsion professor provided are from another professor's old Romanian(?) textbook and are not of the greatest quality (and also use the European convention which swaps the roles of decimals and commas). Google has been surprisingly unhelpful in this regard... For illustration, th
  11. Fiber internet has high fixed costs which preclude its installation in rural areas. I actually did an ethical analysis of mega constellations (full text is here) for my engineering ethics course. From a purely act utilitarian view: From a Kantian view:
  12. True, something built to hold cryogenic liquids should probably be fine. Even icing on the control surfaces shouldn't be a huge deal since they're more like spoilers. I think that the only risk would be buildup of ice on the joints such that the control surfaces are unable to actuate (if they were crazy enough to try and fly in such conditions).
  13. There's a pretty good chance of freezing rain overnight in Boca Chica. The facility's proximity to the coast may help to prevent the ground from freezing, but exposed surfaces (like the entirety of SN10...) will likely get covered in a thin icy glaze.
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