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Everything posted by sevenperforce
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So basically like the new Poodle.
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totm nov 2023 SpaceX Discussion Thread
sevenperforce replied to Skylon's topic in Science & Spaceflight
Header tank is for supplying Raptors, not for RCS. RCS is gas-gas, pressure-fed from boiloff and autogen press of the main tanks. You still need full tank volume. dV for single-stage from LEO to the lunar surface and back again is immense. IIRC the water doesn't come out of the concrete; it reacts with the concrete mix to create the concrete. Quite exothermically, I believe. -
Doing It Artemis Style
sevenperforce replied to sevenperforce's topic in KSP1 Challenges & Mission ideas
It is possible to reproduce a halo orbit in stock using the correct inclination and eccentricity so that you stay just outside of the Mun's SOL at all time. Tough tho. I'll put together a kickass patch. Also note a new bonus...... -
The lander is shown landing on four engines but liftoff is with eight. Multi-engine means multi-engine-out, which I am sure NASA likes. Same concept as Falcon 9.
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totm nov 2023 SpaceX Discussion Thread
sevenperforce replied to Skylon's topic in Science & Spaceflight
That looks...wrong. Like some couples I know. -
It's a lot easier than that. You just need one-way pressure-controlled valves.
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That was my point. You can "throttle" by pairwise startup and shutdown, which means you don't (really) need throttleability for the landing burn. Non-throttleable engines are cheaper, lighter, more efficient, and less fault-prone. However, individual shutdowns and startups don't provide fine enough control to provide immediate pitch and yaw authority. So if they are non-throttleable, then they need gimbal, or the lander needs to rely exclusively on RCS for pointing. If they used fixed but throttleable engines then they have to use RCS for roll but can use differential throttling for pitch and yaw. They can get roll control if they cant out some of the engines slightly, but that introduces cosine losses.
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Hah! In all seriousness I wonder if these engines are intended to be throttleable or not. An easy way to get throttleability is to use multiple engines and shut down some of them, so they will probably be cheaper and lighter if they aren't throttleable. But if not then they'll need gimbal. If they are throttleable then they'll be able to use RCS for roll and throttle for pitch and yaw. Nice catch. A single pump for each quartet of engines is lighter but multiple redundant pumps is more reliable.
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Not quite asparagus bc there are no engines on the drop stages. If I had more time I would pixel-count and guess at the relative prop capacity of each tank. Did Dynetics give any indication of what props or engines it wanted to use?
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Bezos demoed the Blue Moon lander with LH2+LOX and explained that the fuel cells would run off the accumulated boiloff. The human lander descent module uses a pair of engines. I suspect that the accumulated boiloff also feeds hot-gas thrusters a la Starship.
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totm nov 2023 SpaceX Discussion Thread
sevenperforce replied to Skylon's topic in Science & Spaceflight
I think it's a different problem, tbh. Aerobraking in deep passes with control surfaces and a heat shield is very very different from aerobraking in a high pass without control surfaces or a heat shield. -
That's some serious embiggening. Ispy silver spheres covered by radiators. I guess those are the boiloff accumulators for RCS and the fuel cells.
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totm nov 2023 SpaceX Discussion Thread
sevenperforce replied to Skylon's topic in Science & Spaceflight
I have suggested that as well but I do not know much about the long-term viability of multi-pass aerobraking. I have suggested that as well but I do not know much about the long-term viability of multi-pass aerobraking. MRO did it but I don't know of any large spacecraft that has done it at Earth. -
Doing It Artemis Style
sevenperforce replied to sevenperforce's topic in KSP1 Challenges & Mission ideas
My wife just asked me why I burst out laughing. Over 1000 km. You can determine what orbit for your "Orion" will be best positioned for south pole access AND access from Earth. To that end, adding another bonus above. -
totm nov 2023 SpaceX Discussion Thread
sevenperforce replied to Skylon's topic in Science & Spaceflight
Grounded....I see what you did there. I assume he means baking propulsively into Earth orbit? Simple enough if you are leaving from an elliptical orbit and returning to one. Assuming an elliptical orbit similar to GTO, that's just 6.82 km/s. Totally doable with a fully-fueled stripped-down starship. Going from LEO to the lunar surface and back is pushing 11 km/s. Ain't nobody got time for that. I have long been a proponent of horizontal landings on thrusters. They work everywhere except Mars (because Mars needs fully-loaded liftoff). But structural integrity is an issue. -
totm nov 2023 SpaceX Discussion Thread
sevenperforce replied to Skylon's topic in Science & Spaceflight
Those aux engines are just hot-gas meth-ox thrusters. Intended for RCS. Pressure-fed. Throttle those up all the way and use nine of them and you have plenty of thrust to land in lunar gravity. -
I feel like this design is pretty much the perfect baseline for a reusable, bare-bones shuttle. Same set of engines for descent and ascent, efficient use of drop tanks, and easily refueled. Not gonna do anything but get you there and back again, but that's all you need if you have surface assets. Also really good as an emergency, backup departure vehicle. Being so low-slung means you can put a docking port on one side and drive a pressurized rover right up to it. No need for EVA to get into a base.
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Hmm. Hard to figure this out for sure without more data/images but it looks promising. Like a continuous fuel-air explosive detonation. If my guess is right, this combustor is producing a continuous shockwave with an associated choke point, just like the divergence point of a conventional de laval nozzle. So the explosion itself is what forces a low-pressure and high-pressure region. New propellant can be injected behind the shockwave after it passes a particular point. It almost reminds me of the V-3 cannon, though the mechanism is different. Imagine a standard fuel-air explosive. A primer charge has already dispersed the fuel, mixing it with the air, and it ignites from the center. Because of the efficient mixing, the combustion propagates faster than the speed of sound, creating a pressure wave that pushes the flame front further faster and faster. When confined, reflection of these waves means it is shot like a bullet, with the burnt exhaust expanding and rarefying behind it. You get really high combustion efficiency -- what you would expect from something like full-flow staged combustion -- with no turbopump at all.
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totm nov 2023 SpaceX Discussion Thread
sevenperforce replied to Skylon's topic in Science & Spaceflight
Also Elon lost his mind today and TSLA just completely crashed. -
With yesterday's bombshell, we now finally have a good picture of what the Artemis Mission might look like! Only one problem: we still don't know which of the three landing systems will ultimately be selected. That's where you come in. NASA is calling on you to build and launch one of these three landing systems for fun and profit! Baseline rules: Your landing system must be fly unkerballed to a high Mun orbit (Pe > 1000km) and rendezvous with a capsule containing three Kerbals. You can cheat the capsule there if you like. The landing system must then take the crew down to the surface, land safely, allow EVAs, and then launch back to rendezvous with the capsule so that the crew can return safely to Kerbin. I've set this up so that each of the landers offers the same total number of available points, but you go about getting those points in different ways, so it should be fun no matter how you do it. DLCs are fine but no modded parts. Option 1: Kynetics, A Keidos Kompany Launches from Kerbin sideways, flies upright - 20 points Eight ascent/descent engines - 10 points Expends two drop tanks - 15 points Able to be reused by attaching new drop tanks (demo only) - 30 points Uses dual tall solar panels - 12 points Lowest weight of any Option 1 submission - 30 points Looks most like render (I judge) - 20 points Option 2: SpaceK Munar SkarSkip Single-stage, launches on a single booster - 20 points No monoprop thrusters - 10 points Uses nine separate canted-out landing engines - 15 points Refueled in orbit - 30 points Uses fixed solar panels around a docking port in the nose - 12 points Lowest part count of any Option 2 submission - 30 points Looks most like render (I judge) - 20 points Option 2: Kational Team Three separate modules assembled in munar orbit - 20 points Two engines on the descent stage, one on transfer and one on ascent stage - 10 points Capable of landing successfully on only a single engine - 15 points All modules launched on the same rocket - 30 points Transfer stage remains in low munar orbit to take the crew back to the Earth Return capsule - 12 points Physically shortest stack of any Option 3 submission - 30 points Looks most like render (I judge) - 20 points Good luck! Bonus points (cumulative, all entries): Land within 100 km of the south Munar pole - 30 points Land on a crater rim - 20 points Land at the highest elevation of any entry - 50 points Deploy science packages carried on vehicle - 10 points Deploy a rover - 20 points Lowest dV used to get from trans-munar injection to your "Orion" and then to low lunar orbit (Ap < 20 km) - 35 points All reaction wheels disabled - 45 points Leaderboard:
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Assembly is easy enough. Keep the drop tanks attached to the LV upper stage and have the spacecraft come mate.
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@tater we were right
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Maybe Orion+EUS was borrowed from Marshall but lander+EUS was done in-house? Ah, here's stuff from the presser: Reuse? So it only goes up once and then gets refueled?
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I'm just saying that these two renders look rather different: But maybe they borrowed the lower render.
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No, look closely; the intertank is different. I think it is expected to launch on Vulcan-ACES or something similar, not EUS. The sideways-launched lander with drop tanks is almost exactly what I proposed a few months ago.