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About farmerben

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    Sr. Spacecraft Engineer

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  1. I'm gonna drive around Mars in anything, pulling a spike tooth harrow and some rare earth magnets. Every hour I'll collect several kilos of ferrous-ferric oxide. Pulverize it into nanoparticles. Make a ferro-fluid with a solvent like methanol and some epoxy. Put a strong magnet inside a dome and make this on the outside Possibly the hardener is Martian CO2, or maybe the evaporation of methanol results in hardening.
  2. Save on bags. Save on concrete. Definitely save miniturized lava smelters. Mars has clay
  3. The digging drums they put on that Voltron unicycle device look crazy to me. So we spin our payload over an over just so we don't need another truck? Spin one direction to pick stuff up and the stuff in there won't fall out...? Really? Doesn't stuff bounce around. Seems very likely they will crush and scoop a large volume of material, waste most of it, and come home 10% full. These things have to be huge. They need so much torque to drive the wheel so it doesn't jam up on every boulder. The real advantage is the continuous stream of payload on a conveyor. Which can be more economical than a fleet of trucks and loaders jostling back and forth. If the goal is to move loose ground from point A to point B. A scraper is better.
  4. A hydrazine pressure system could forego turbopumps and helium inflation systems in exchange for a much simpler system. We can take heat and convert our fuel into hydrogen and nitrogen without opening any loops. Running the main engine hypergolicly at full power gives plenty of heat. Turbomachinery not required.
  5. They definitely do this, and it works as you say,. But, I'm not sure if it's fast enough for first stage boosters. I've also heard the helium bladders are required to prevent the fuel tank from imploding in atmosphere, which it could do with a powerful enough turbopump sucking on it. Hypergolic-monopropellants offer some interesting oppotunities. N2H4 transitions into N2 and 2H2 irreversibly, and with substantially less heat that combustion. So it could be fed back into the tank as a pressurizer. N2O4 breaks apart in a reversible manner, so it is a different beast entirely. I don't have certainty on this, but it seems to me that: Hydrazine and dinitrogen tetroxide could support unique types of fuel pressure systems that do not work with more stable fuels. And there is a possibility reducing weight and number of parts by doing so. Somebody has probably already thought about this and written a paper on it. If you know about it tell me.
  6. In this picture it looks like the pump exhaust is hydrazine rich.
  7. This is an LR-87 engine from the Titan II and Gemini programs. It uses open cycle fuel pumps with their own exhaust pipe. If what I"m reading is correct. This engine with very small modifications could run on RP1+LOX, H2+LOX, or Aerozine 50 plus Nitrogen tetroxide. My understanding of open cycle fuel pumps is that they have to run fuel rich to not overheat, and because oxygen is highly corrosive to steel. The hypergolics do not have those particular problems. It seems as though it would be easier to close the fuel cycle with hypergolics (particularly since the fuel and oxidizer have a monopropellant capability before they are even combusted). Did they not go for closed cycle just because they were in a big hurry? Were they exhausting hydrazine rich gas through that tube into the open atmosphere?
  8. The video at the top is one of the least plausible theories for pyramid construction I've seen. The pyramid blocks are smaller and moved over less difficult terrain than some of the ancient monoliths. A 3 ton block can be lifted with about a 1 inch thick rope and a wooden tripod. I don't think Herodotus' description of the ramps was accurate. The only ramps you need are wooden rails running directly up the pyramid at 51.5 degrees. The Incas moved some monoliths up ridiculous slopes. I do not believe they used ramps or hoists for the most impressive lifting. I think they used levers and cribbing. The motion is similar to rowing a ship. The levers lift the stone and can shift it forward a few inches at a time. This allows cribbing to be added one board at a time.
  9. This is actually genius! Soap bubbles would get sucked toward any leak. The part that doesn't outgass or freeze becomes like wax. While glue is attractive, just plain soap has the advantage of being able to easily decontaminate the equipment and recycle the soap.
  10. If you want inflatable storage space, it could be built far lighter than a habitation. The rigid hull can be crammed full of gear initially, if we plan to put that gear in the shed once in space. Do you have experience with bad air mattresses? It takes less than 1 psi to establish the fully inflated shape. Micrometer sized holes leak noticeably over periods of hours. Over brief periods of time they seem to work well. If you leave it on the floor without weight for many days, the shape is still somewhat expanded. A space shed works well in conjunction with an airlock. A very tiny amount of air pressure would allow an astronaut with a breathing mask and a flight suit to work in there. Deflation equipment allows us to recover most of the air before it escapes into space. We will not disrupt the shape of the inflatable by sucking air out of it. Only shadows are going to change the shape of our inflatable from now on.
  11. This is the only serious disagreement I have. I think the total impulse will increase, the more mass is packed around the charge. For a given amount of energy heavy slow stuff has more momentum than light fast stuff. Is the jet going to be effective going through material? These explosive units are similar to bunker busters, capable of cracking hardened bunkers dozens of meters underground. They are based on HEAT warheads that move a well shaped jet through armored steel. That is different than in a gas, and gas is different than plasma. The nearest thing I can compare it to is ball lightning, and that is not very close. I would expect the shaped charge plume to work reasonably well in atmosphere. If it doesn't oscillate the same as in vacuum (pancake-cigar-pancake), it at least goes (pancake-hourglass-broccoli). Wikipedia currently mentions setting off the charge 25m behind the plate. So we have some room to tune that variable. Can we get useful thrust? That is the question. How much potential thrust is wasted? Doesn't matter within wide margins. As for protecting the sides of the ship. We need mass for mechanical reasons, more than we need armor. Preferably attaching as much mass as possible to the plate, rather than the payload.
  12. How much though? Some of the forward impulse would flow around the ship, resulting in waste, and maybe damage? It was the observation that steel survived near ground zero and showed fingerprints on it, that convinced the Air Force to pay for it. The speed of the shockwave front is based on the average velocity of particles squared, so it falls as 1/distance2 . Pretty quickly you'll be surfing one shockwave at a time and outrunning all the previous pulses. Energy is not actually a constraint in this case, because boosting yield with tritium is easy. The total impulse in the forward direction is greater in atmosphere than in vacuum because the total rearward impulse of stuff other than the ship and the tungsten is greater.
  13. The moon has variable amounts of radon, with both space and time. The radon is not always correlated with detectable uranium near the surface. The radon is not emitted at a steady rate, disturbances of the crust (such as thawing and meteorite impacts) have an effect.
  14. They thought it was possible to go from Earth's surface to orbit with about 80 pulse units. With fission set at the lowest possible levels these 80 units would create about the same fallout as one normal atmospheric test of a megaton weapon with a fissile case. Or about 1/300 the fission product fallout that humans had already put into the atmosphere around 1960. Which sounds not that bad. The EMP effects were barely recognized early on. I disagree that only the momentum of the tungsten membrane counts toward thrust. All the hot plasma striking the pusher plate contributes thrust, as well as ablatives on the plate itself. Filler material helps capture radiation energy and turn it into plasma heat, atmosphere increases effective filler material. In vacuum the tungsten plasma projectile has nearly all the useful momentum, but a tiny fraction of the energy from the explosion. Most of the energy is radiated away without creating a shock wave or fireball, as it does in atmosphere.