Loren Pechtel

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About Loren Pechtel

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    Senior Rocket Scientist

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  1. It's not actually your center of gravity that matters, but rather the angle between the ground and the center of gravity. The smaller the angle the more stable the rover. Putting your mass low helps but it also helps to make your rover big. It will be a pain to haul to orbit but it's a lot less likely to crash. Also, if you're willing to spare the mass & power, use reaction wheels. Bring along a pilot or probe core capable of running SAS. With SAS on it will use the reaction wheels to try to keep the rover from flipping. I've taken rovers with big reaction wheels over terrain where you end up sliding down a hill--when sliding you can't hope to be careful and thus any ordinary rover will most likely crash.
  2. I'm not contradicting myself. On launch a rocket goes straight up, then soon tips with the rotation of the body and accelerates to orbit. This is the lowest energy trajectory, you want to do the exact reverse to land with the least fuel. The first burn puts your periapsis a bit above the point where you want to have killed your horizontal velocity (the reverse of your circularization burn.) You then come in, lighting your rocket at the point it will kill your horizontal velocity over your target. This of course means you end up lower than the orbit you were in, hence the reason your periapsis is higher than your objective. As you approach your target you tip more vertical as you can't just suddenly turn vertical when you complete your burn. (Now, if you have a small rocket with the vastly-overpowered rotation capability of many such rockets in KSP you would be better off not rotating until you're over your target.) You still have substantial vertical velocity at this point, optimum is you shed it in a suicide burn. This isn't what Apollo did because they took the safe route. Their approach burned considerably more fuel, though.
  3. I don't think keeping the downward momentum under control is what you want. You want to leave the burn for as late as possible. The ideal landing is a gravity turn in reverse. Without knowing exactly how the rocket will perform you can't do that precisely, though, so you're going to need to allow some margin.
  4. A "transfer window" normally refers to a situation where you have three bodies involved. The math is imprecise and much more complex than what you are thinking of with a Hohmann transfer. For a Hohmann transfer you simply need to find when you're at a point directly opposite where your target will be in half an orbit. (If that gives a negative solution you missed it, look for the next such point.) Things like Transfer Window Planner and the similar functionality in MechJeb, however, are looking at a more complex problem. 1) Your target is in another SOI. The simple math of a Hohmann calculation won't give the burn you need. 2) As there are three bodies involved (the ship, the starting planet, the arrival planet) there almost certainly isn't a perfect solution. At the point your planets are lined up perfectly it's almost certain your ship is not. Thus, rather than a simple equation that spits out one answer you have a much more complex equation that must be tested over a whole range of values in order to find acceptable missions. For a Hohmann burn the fuel use for a non-optimal burn goes up very rapidly as you get away from the optimum, you're going to want to do such burns as close to perfect as you can. For an interplanetary burn the penalty goes up much slower, in general waiting around for your spacecraft to reach the correct point in it's orbit for the burn is going to have a very minor penalty. (However, if you're orbiting near the edge of Eeloo's SOI and try to burn for Moho the error is so big you might as well forget about it--exit Eeloo's SOI on the inward side and then do it as a Hohmann maneuver.) You can even send a fleet doing it one spacecraft per orbit without a big penalty. (Just make sure their arrival times are also staggered as you can only fly one craft at once!)
  5. Stages are only recovered when they go below the IIRC 22km line. A stage that doesn't go that low will simply remain in "space" (even if it is actually orbiting entirely in the atmosphere!) and not be recovered.
  6. I would like to see a few changes: 1) The higher the Kerbal's level the longer they should be willing to be on a mission. 2) The submarine has a lot of people--I think that matters. The more Kerbals around the longer they should accept the situation.
  7. I can't address whether the propellant goes down or not but your evidence doesn't prove it. The jetpack contains a ridiculous amount of fuel in stock. You can get to orbit on Minmus with your jetpack alone, no need to refuel. One refueling (and note that a canister is supposed to provide enough for two) will get you to orbit on the Mun. (Note that the Basic Orbit mod will make it much easier to do this, it lets you see your orbital parameters in the close-up view.) In versions past I have done orbit-Minmus-orbit with one fuel tank and orbit-Mun-orbit with two. Admittedly, I'm not good enough to accomplish the landings without a reload or two.
  8. Later messages seem to indicate you solved your problem (there's a reason it's recommended to uninstall old versions of mods before installing the latest!) I do have a comment about your mission profile. This sounds like you're just hauling tourists to orbit. It also sounds like you have decouplers. Assuming you have radial parachutes may I suggest an alternative design that would provoke outrage at NASA but it will fly: Put your pilot in a capsule, put your tourists in the crew module (meant for aircraft but it works in space), take a heat shield and invert it and stick it on the nose of your rocket. Then attach a decoupler and a nose cone. Simply putting a capsule on top of crew modules is very prone to lawn-darting a heat shield on the front will create enough drag that it will slow anyway so long as it's not too long. If that's not enough you can provoke even more howls from NASA by radially mounting more crew capsules--each needs the shield/decoupler/nosecone setup but you can fly it with only one command pod (although if it gets big enough adding a reaction wheel is a good idea.) I have flown suborbital tourist contracts with a slab of 5 stacks of IIRC 3 capsules as one rocket. (Note: I modified the number of available contracts, with the stock game you can't have enough tourist contracts active to fill such a bird.)
  9. When you see things set up in powers of 2 like this you should automatically think bit flags--you can add together any combination of them and yet tell exactly what numbers were added together. It's the most efficient method of packing such information and given that the author used it pretty much implies there was a lot of data to keep track of. The storage units that such things get stored in have standard sizes of 8, 16, 32 or 64 flags, each of which uses twice as much memory as the next smaller size. Also, KSP mods are written in C# and while it supports 64 bit unsigned values they can be a hassle to work with because the compiler is so strict about not allowing anything it thinks could possibly be wrong.
  10. Are you sure the stage isn't still up there? KSP's destruction threshold is well below the top of the atmosphere and objects on rails do not experience drag even in atmosphere. If your periapsis is above I believe 22km the stage will remain in orbit--even if that entire orbit is within the atmosphere! (Careful--remember that you can't switch away from an object in atmospheric flight. Switch to such a booster and you have to stay with it until it burns or goes splat.)
  11. You made a typo and said KIA (a Korean carmaker) rather than KIS. I decided to have some fun with it.
  12. Well, if you want to install a car into a spaceship you need the SpaceY mod!
  13. You simply set Steam to load the "beta" that is 1.5.1. Now, if you're talking a pirate version, it's too good a game for that, walk the plank!