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Armchair Rocket Scientist

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    Sr. Spacecraft Engineer

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  1. This all makes sense - I figured the mass of associated equipment would be approximated by the case mass and/or the density used for the part. However, the results I'm getting don't seem consistent with it just using the area density and canopy area. As an experiment, I edited ParachuteMaterials.cfg to reduce the area density of all materials by a factor of 100, then made a RealChute with an extremely small size, and a ridiculously small parachute with a 3 meter diameter. The parachute mass should be negligible - which was confirmed by the part mass hardly changing at all with changing chute diameter, and the case mass is only 3 kg. However, the total part mass is still about 0.303 tons. Do you have any idea where this extra mass could be coming from? Screenshot showing the anomalous part mass.
  2. How is the parachute mass calculated? My chute masses don't seem realistic. I am using RealChute, FAR, and Realism Overhaul, and attempting to make an Orion-like spacecraft. According to various NASA articles, each of the Orion's three main parachutes weighs about 300 lb (136 kg), is 116 ft (35 m) in diameter, and slows the approximately 9 ton capsule down to around 20 mph (9 m/s). However, testing with a 35m diameter nylon RealChute, using the Radial RealChute at the default size, with an approximately 3 ton spacecraft, the part mass was approximately 0.43 tons. Its performance was close to reality, reducing the craft to 7 m/s at sea level. Additional testing using a 3m conical RealChute with a 71m diameter (equivalent area to the three parachutes on the space shuttle SRBs) and a landing mass of 90 t (equivalent to the descent mass of an SRB) resulted in a total chute mass of 0.512 t, of which 0.288 t was the case - this is compared to the SRB main parachutes weighing 3 tons in total. Again, the parachute's performance was realistic, with an impact speed of 20 m/s, but the mass was far different from reality. Is there a way of fixing this to get parachute masses comparable with real spacecraft?
  3. Is there a way to use Realism Overhaul for realistic solar panels, electricity consumption, and so on, but without rescaling parts like command pods to human-size, and using the Stockalike RF engine configs? I'm working on an install with roughly 10x upscaled planets, and I want all the physics and part performance to be as realistic as possible, but keeping the multiples-of-1.25m scale factor, as appropriate for meter-tall Kerbals. I know the answer is probably somewhere in the configs, but I wanted to confirm that deleting the Engine_Configs folder that comes with RO and replacing it with something else won't break everything, and I can't find which config has the changes to parts like command pods and reaction wheels.
  4. [quote name='wumpus']Just how many pound draw do you need to fire an arrow at orbital velocity? You aren't going to hit the Earth from ISS with any bow pulled by mortal man (ignoring slow, slow air resistance).[/QUOTE] No amount of draw. As you make the bow larger, it gets heavier, and the body and string of the bow have significant inertia. Ultimately, for a given bow design the speed will be limited by material strength and density. Maybe with some extremely complex design you could get an arrow to go supersonic, but orbital velocity is comparable to the detonation speed of high explosives. I'm not sure how you'd get any material to elastically rebound at those speeds.
  5. [quote name='Cirocco']I made a thread about this in the space lounge as well and I'll repeat the same arguments here: this landing has almost nothing in common with what SpaceX is trying to do. The falcon 9 is designed to boost a payload + upper stage halfway to orbit. It's far, far, FAR bigger, heavier, more flexible, its engines don't allow it to hover like the New Shepard, etc. SpaceX has to overcome a whole lot more difficult problems. That being said, this [I]was[/I] a historic event: it was the first rocket that passed the Karman (I swear I almost typed Kerman there) line and come back down to land safely. The team behind it definitely deserves all the recognition and credit for that. And I definitely agree that the civil response from musk would have been to say "hey, good job on achieving your goal. Now we're going to go back to work on ours". I have great admiration for what Elon Musk has done and continues to do to drive technology forward to a more sustainable future, but I really dislike how he reacts to these sort of things, or to people investigating technologies or things he considers not worth researching.[/QUOTE] It was the first rocket that passed the Karman line and safely performed a propulsive landing. Sounding rockets (and amateur ones) have made safe parachute landings from beyond the Karman line.
  6. The simplest answer: you can't simply "deal with" this problem because it's part of physics. If a vehicle is aerodynamically stable flying nose-first, then it will be travelling nose-first when the parachute deploys, and subsequently have to "flip" around. There are only two ways to "fix" this. 1. Deploy the parachute from somewhere other than the nose, resulting in an "on-its-side" descent attitude. This is similar to the "rogallo wing" concepts for Gemini, as well as ballistic chutes for airplanes. For a capsule, you're lying on your back in normal flight, so with the capsule on its side you're sitting upright. For an airplane, the vehicle is in close to its level flight attitude. You can also deploy the chute from the tail, but for a manned vehicle you'd be hanging upside down for the descent so this is usually avoided. 2. Make the vehicle aerodynamically stable flying tail-first. This is what all "capsule-style" manned spacecraft do: during a normal reentry and descent, when the parachute deploys the spacecraft has already jettisoned the launch vehicle, service module, etc. and is already falling with the heat shield pointing downward. The only time something like this could come up in manned flight is during a launch abort scenario. In [URL="https://www.youtube.com/watch?v=AMdYAg5mrnU"]this video[/URL] of the DragonRider's pad abort test, when the trunk, which includes fins to keep the vehicle stable nose-first during the LES burn, is jettisoned, the capsule violently flips over, although this is due not to the parachutes but due to it now being stable in a heat-shield-first attitude. The parachute deployment causes additional rocking and swaying. However, while it might be uncomfortable, this is definitely survivable, and would only occur in a launch abort scenario where crew discomfort and minor injuries are acceptable.
  7. [quote name='SomeGuy12']If you wanted to dock to a rotating station along the rim, cuz you're crazy...can it be done? Let's see...if you draw an imaginary line out in space representing a tangent coming off the rim, and then position your spacecraft along that line, I think it would become an intercept problem. Suppose there's a particular docking port that passes a point on the tangent line with every revolution. You want to match velocities with the rim speed, and then arrive at the intersect point between the tangent line, the station, and the docking port at exactly the right instant. Assuming constant station velocity and a known distance, this is a pretty simple intercept problem. So you just jet on over, matching velocity during the initial burn, then at the very instance your docking apparatus (something that can grab really fast, like big honking electromagnets I guess) achieves closest approach to the station, at that exact same instance, the docking port revolves underneath it. A gigantic surge of current and the magnet sticks you to the station. The problem is you go from 0 acceleration (just coasting through space headed for the rendevouz) to 1 G instantly. A huge jerk. It seems like this might also be bad for the structure of your spacecraft and the station. Maybe shock absorbers could smooth it out? On the bright side, the actual rendevouz is easy. You can trivially monitor the relative position of the station wheel as you approach on computer control, via optically checking against markings on the wheel. Radars give your exact velocity of approach. You can easily fine tune your approach as you get closer, and if something happens to where the rendevouz will be missed, you just need a puff of RCS to push you away from the station so the closest approach is more than 10 meters separation. The timing is only difficult if humans have to do it. The hard part is the mechanical coupling and the whiplash.[/QUOTE] Docking with the rim of a rotating station would be incredibly easy. Just make the rim significantly wider than the spokes, or build it without a hub. Then put maglev rails on the inner rim. The docking spacecraft maneuvers up to the rails as slowly and carefully as it wants, then clamps onto the rails and a braking system on the station automatically slows it down, at which point it is switched off the main rails to a docking bay. For undocking, the process occurs in reverse, with the spacecraft being catapulted backwards until its "true" velocity is zero, then unclamp from the rails and fly off with RCS. Heck, you could even build an actual runway on a station and land a spaceplane on it, although taking off would still need a catapult.
  8. Depends on how much payload and how much time. A major constraint on a mission like this is that the power output of RTGs gradually declines: making a probe that gets to Sedna 50 years after launch isn't necessarily that useful. How big is your course correction? Your probe is going to be going FAST when it flies by Quaoar if you want to reach Sedna in a reasonable timeframe. Even a tiny change in direction could end up costing multiple km/s of dV (which is a big deal for a small probe). Now, I have a question of my own: Why Sedna? We've already done a flyby of Pluto, so we have a decent idea of what TransNeptunian objects look like. Yes, Sedna's weird orbit raises a lot of questions, but how many of those could be answered by a flyby lasting just a few hours? And there are many other promising targets for flagship missions, including long-duration exploration of Europa, Titan, Enceladus, Uranus, or Neptune. If you want to make a serious mission proposal, you need to do two things: first, show that it is technically feasible, and second, justify spending money on your mission instead of the other mission proposals competing for the same funding.
  9. https://en.wikipedia.org/wiki/1997_Pacific_hurricane_season https://en.wikipedia.org/wiki/1997_Atlantic_hurricane_season
  10. Environmentally a terrible idea, and according to the wikipedia page it would have required "six new nuclear power plants" to pump the water over the Rockies. Desalinization plants would likely be cheaper and more environmentally friendly, especially since much of the infrastructure could be built in desert areas.
  11. I don't think 57 solar masses is enough to exceed the Eddington limit, since there are stars over 100 solar masses.
  12. How do you know it isn't behind us? Say, that the probability of a species developing to the point where it's capable of forming a technological civilization is extremely low, and very few planets have agriculture, much less Dyson Spheres.
  13. There are plenty of altimeters designed for amateur rockets that will read up to 100,000 feet with barometric sensors. Note: Don't use these on a balloon. They have high sampling rates (meaning they probably won't record hours of flight) and use accelerometers to detect a launch: the gentle ascent of a balloon probably wouldn't do much. You should be able to find Arduino-compatible pressure sensors with that resolution. I'd also advise asking this question on DIYDrones or another amateur weather balloon forum: they'll be much more able to help you than this forum.
  14. There are several problems. 1. Your grid must be separated from the floor by at least a few millimeters, be strong enough to support the weight of people and furniture, and be fine enough to not be unpleasant to walk on. Does this even exist? 2. You still have to clean the grid itself. Using GMO organisms for more efficient disposal of trash is a decent idea, but it's better to just use a composting vat. If you want an environmentally way of cleaning off objects, don't bother with a whole slime mold in your house: farm the desired microorganisms for their digestive enzymes and use the enzymes in cleaning fluid to replace less environmentally-friendly chemicals. I'm pretty sure there are already enzyme-based dish and laundry detergents, pet urine smell removers, etc.
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