Loren Pechtel

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About Loren Pechtel

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    Senior Rocket Scientist

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  1. I can think of a legitimate case for something to have solid fuel without being an engine. There's a mod that adds landing rockets. AFIAK they're not reloadable (although you can put it's controller on a rocket and use normal liquid engines, which obviously do reload) but what if KIS-style reloads for the rockets were made?
  2. In my experience the MechJeb oscillation problem is a derivative of the underlying game oscillation problem. You need more control authority. What happens is that it does not correctly figure out when to start countering a turn and overshoots the target--so now it goes in the other direction. If the control authority is low enough it overshoots by more each time. I have seen this is stock with an EVA kerbal. Turn the jetpack way down and tell the Kerbal to stabilize.
  3. And another one from 1.4: The third stage of this rocket is Nerva. On the pad it showed about 3000 m/s in it. By the time it lit off in orbit it showed about 5000 m/s in it, which is what it showed in the VAB. The atmosphere and vacuum numbers were always the same.
  4. (Note that I hit this on 1.4, but I don't see anything about it being fixed in 1.5) Advanced transfer to another planet--I got the porkchop showing values that I expected, tried to create the node and it failed. After a moment's thought I realized what was up--I was in a polar orbit (science mission going from the Mun to Minmus.) Obviously the porkchop was drawn without actually looking at my orbit but the node creator didn't know how to cope with my orbit as I was never pointed in the right direction. I wonder if this might be related to some wacky burns it's tried to set up in the past.
  5. Loren Pechtel

    1.4, how do I cool the Nerva engine?!?!

    No--those numbers are from the radiator, not the engine.
  6. Loren Pechtel

    1.4, how do I cool the Nerva engine?!?!

    Things get stranger and stranger. I unlocked the graphene radiators, put 4 large ones on (there's one Nerva engine) and tried it. Things finally appear to be stable, each radiator is dumping 20kw of power. However, they are showing: Rad Temp: 199.6K/2698K Part Temp: 1507.1K/2698K Core temperature: 1507/1210K Skin temperature: 1331/1210K What's really going on with the heat? 1507.1K/2698K looks fine but what are the other temperatures? 1507/1210K should go boom but it's flying fine. (And why do the pesky things want to deploy on the pad?)
  7. Loren Pechtel

    1.4, how do I cool the Nerva engine?!?!

    I guess I need to unlock another level of cooling. I don't have those yet.
  8. This is driving me nuts. I'm trying to send a scientific mission to orbit the moons. On 1.2 I had no problem, slap a few radiators on and it works fine. Now, however, I have yet to come up with anything. I've attached every radiator I have to the fuel tank above the engine, they accomplish almost nothing--a few hundred watts of heat per radiator. I think something must have changed in the physics.
  9. Loren Pechtel

    Rentering with passenger cabin problems

    You don't even need a capsule at all. It's perfectly acceptable to have everyone in passenger compartments. Something I did once that worked reasonably well for a suborbital flight was to put decouplers on the top of the rocket and nose cones on them. Blow the cones and re-enter sideways (so long as the reentering bit is symmetric head-to-tail you can do this pretty well) for as long as you have the control authority. I never tried that with orbital flight, though.
  10. Going to space is easy?? I came up with a design that I think could have both flown and landed. Unfortunately, it was unflyable due to control oscillations--MechJeb's usual 90 degree turn ended up being more than 180--and the return even more--each twist getting farther off and it tumbled before reaching 20km.
  11. Yeah, but long, nose-heavy craft that land in water are in trouble. It's a balancing act for which I haven't yet found the right balance.
  12. I remembered this mod and decided to see if it would allow me to reliably land a pesky beast--lands safely on land, but bounces back up and blows up when it lands in water. From your description of the math it's probably going to do it wrong--but in this sort of case I think the math is being done wrong. You're assuming the rocket is falling and it's a purely propulsive landing--but a good use for this is like on the Soyuz, reducing the landing speed of something that's already under chutes. 1) Figure the rocket is already at terminal velocity (there's no reason for suicide deployment of chutes), without the booster it will not accelerate. 2) In computing the burn effects apply planetary gravity at velocity zero, zero gravity at the rocket's current velocity, the curve is a y=x^2 over this range. 3) Provide an offset number, initiate retrofire this many meters above/below the computed point--let us tweak it for a particular rocket if the math isn't spot on. 4) How about some stack-mounted versions?
  13. This thing is driving me nuts! I rebuilt it lowering mass in the part that's recovered--and now it won't fly even with some big steerable fins on it. Oh, well, I guess I have to make it fatter and shorter.
  14. This game hates me! While my rocket insists on turning prograde the instant the booster comes off the fins will slow it fine. If it comes down on land, fine, but if it goes into the water it pops up to turn turtle and blows up (and where did that fireball come from? There was no fuel on board!) when it hits the water coming back down. I'm going to have to rearrange the recovered portion to lower the center of mass.
  15. Interesting. It never occurred to me the doors would survive the fire.