dantedarkstar

You have to switch to "grab" mode (which results in the little green hand cursor when over part) by pressing G to move any anything already placed in world around. I think I seen that in the manual though.

High/over-powered solid rocket motor ascent vehicles, that go into orbit in a literal blaze of glory. TWR 2-3 at launchpad (usually around 2.3) and growing (sometimes getting to around 10 before stage burnout). Playing with FAR, I found out that "hot" (turning into fireball usually around 10km above ground) ascent vehicles use up less dV total than "cool" ones (those that don't produce hot plasma sheath on their way into space). Quite specific to fly, because is you don't (sometimes aggresively) help gravity with the turn, you end up with 200-500km apoapsis and not enough fuel in the last mini-stage to raise periapsis up to space.

Now that this was mentioned, I don't see any fundamental reason why there couldn't be a turbojet engine that uses both fuel and oxidizer to produce thrust in any gaseous atmosphere. There's nothing magic to it. Turbojet (or even better turbofan) are so efficient not because they don't have to carry oxidizer (then they would have just around 2 times more ISP than rocket or so, depending on relative weight of oxidizer and fuel) but because they use lots of atmosphere as reaction mass to push backwards. So taking a turbojet and modifying it so that it supplies both fuel and oxidizer, should allow an engine with half ISP of traditional turbojet but not relying on atmospheric oxygen. Actually there probably would be some real issuses, like oxidizer and fuel being hard to burn if they are both sparse in inert gas. I think this could be solved though, perhaps by making it more like "rocket-turbofan engine" where the core is essentially a rocket, that uses inert gas added to rocket exhaust to cool it down enough for the turbine, which drives large fan found in typical turbofan engine, which provides majority of thrust. Or maybe by using monopropellant-powered turbojet ? (then the issue of fuel not burning because both fuel and oxidizer are too sparse wouldn't exist at all) I suppose we never saw anything like that in reality, because we are nowhere near the point where we need such engine. Unless of course somebody with actual experience in turbojet engineering could point out fatal flaws in my reasoning that I don't see.

Geschosskopf, I still hold that you are wrong. Let me explain it again. Assuming no irreversible processes happen (like atmospheric braking) then spaceflight is *fully* reversible. There is no time arrow defined -- if time is reversed, we couldn't tell (as we can for example for thermodynamic processes like gas escaping from container into space since reverse process is HIGHLY unlikely), since the dynamics would be exactly described by the same physics. This means that considering going from different APs to same PE is *exactly* equivalent of going from PE to different APs. Of course this ignores atmosphere, but since you are going to the same predicted PE, it ignores atmosphere anyway. So let's assume that Kerbin has no atmosphere for a moment, and just track how much of the trajectory is "below 70km" or any other set altitude. Then my previous claims hold true. The higher velocity at given fixed PE, the higher the AP, but at the same time less curve and therefore trajectory always above the lower-velocity trajectory. We have 2 trajectories (both are after any burning you did at AP, so both are ballistic trajectories from that point): A) from AP 12Mm to PE 37km, B) from AP 1.5Mm to Pe 37km This is exactly equivalent to trajectories: C) from PE 37km to AP 12Mm, D) from PE 37km to AP 1.5Mm. It should be obvious to anyone playing KSP that trajectories A and C have the same velocity at periapsis, and that velocity (Va=Vc) is higher than the periapsis velocity of trajectories B and D (Vb=Vd<Va=Vc) (can't cheat conservation of energy without burning engines, which I assume you don't do except at AP to adjust PE). If your velocity is higher, then the curvature of the trajectory (at a given altitude) MUST be smaller. This is because the gravitational force is proportional only to masses and the distance from the body that you are interacting with. And the mass of the object itself cancels out when calculating acceleration, so it only depends on mass of the planet and distance form the planet center -> altitude. Given higher velocity, the curvature must be smaller = larger curvature radius, as described by r = V^2/a (this is simple relation for circular motion, but if we consider local curvature then it works as well), since a = acceleration from gravity which is the same for both A/C and B/D trajectories. While it is obviously possible to draw an ellipse of higher eccentrity (and higher AP) with same PE, that is also narrower, such ellipse is not a physical trajectory and will not have Kerbin as one of focal points (which is always true for trajectories in point gravitational field, as calculated in KSP). In the below picture, the low AP orbit (actually lowest possible, since it's circular) is blue. The high AP orbit is NOT the red one that indeed would spend more time in atmosphere, but the green one, which is always above blue one, except at PE. Black points are supposed focal points of the ellipse. Note that the red one does NOT have focal point at the center of Kerbin (cyan circle), since PE is always *closest* point to the focal point which must be (according to physics) the body with gravity field (so by definition PE is closest to focal point). An even higher AP ellipse would be again wider around kerbin and always above green trajectory. [IMG]http://i67.tinypic.com/24o9b0o.png[/IMG]

[quote name='Geschosskopf']I think you misunderstood me. I have the same Pe (37-38km) on both the 1st and 2nd passes. I do the 1st pass, at Ap raise the Pe back to where it was, then make 2nd pass. On the 1st pass, the Ap is way out near Mun or Minmus so the orbit is very eccentric. On the 2nd pass, the orbit is much more circular although still eccentric (Ap ~1.5Mm). So while on both passes the ship is in the exact same "layers" of the atmosphere (70km down to 37-38km), on the 1st pass the high eccentricity causes it to spend more time in the atmosphere, nearly 1/2 of Kerbin's circumference. Wth the 2nd pass, the ship WOULD only be in the atmosphere for about 1/3-1/4 or so of Kerbin's circumference. However, actually it never exits on this pass and lands about 1/2 to 2/3 of Kerbin's circumference from where it entered the atmosphere). [/QUOTE] You are wrong. If both passes have the same periapsis, then the one with higher apoapsis ALWAYS spends less time in atmosphere. Since dynamics in space is reversible, make a thought experiment. You are starting from periapsis, and setting your velocity to some arbitrary V0. If V0 is higher, your trajectory will be always flatter (less curved) and therefore at any point further away from Kerbin than the lower-V0 trajectory, right ? Now, as we all know, the higher the velocity, the higher the apoapsis. Hence the high-apoapsis trajectory is always flatter near periapsis and therefore spends less time in atmosphere. Which means that the higher the starting point of a dive, the less distance will be through the atmosphere, provided the periapsis is the same. Of course it is possible to do higher dive with more atmospheric time, but it will always require lower periapsis. Higher apoapsis = less distance in atmosphere, given fixed periapsis

He's in captain's seat of the ~200ton Shai-Hulud spacecraft scheduled to burn towards Duna as soon as enough fuel is supplied, and expected to be commanding the mission to Jool next (probably).