<Bornholio>
done mars manned landing three times, fly by twice
<Bornholio>
pretty much have to have nukes and isru helps a lot, propsitioned tankers otherwise. Manned martian moons are easy peasy compared to full landing on mars
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<soundnfury>
Bornholio: one of these days I'll get round to installing RealISRU...
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<Bornholio>
I need to poke someone to push my PR and make a release
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<awang>
Bornholio: PR where?
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<awang>
lamont: MJ PR created!
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<ProjectThoth>
What exactly are steering losses?
<ProjectThoth>
MechJeb defines them as "esselState.deltaT * vesselState.currentThrustAccel * (1 - Vector3d.Dot(vesselState.surfaceVelocity.normalized, vesselState.forward));" but I don't know how to parse that.
<ProjectThoth>
Change in time * Acceleration(From thrust), then ?.
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<BadRocketsCo>
Howdy
<Qboid>
BadRocketsCo: soundnfury left a message for you in #RO [31.10.2017 23:51:35]: "no mars here, I usually restart before getting to lunar flaggage. Think I might have done a venus fly-by once, not sure."
<BadRocketsCo>
Hmmm
<BadRocketsCo>
I'm trying to figure out a manned interplanetary transfer vehicle
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<awang>
ProjectThoth:
<awang>
Er
<awang>
Hit enter too early
<awang>
looks like it's calculating the amount of dv you're spending thrusting not-forward
<awang>
So if you're pointing prograde, no steering losses
<awang>
Pointing completely sideways? Everything is steering losses
<awang>
dt * acceleration = dv
<awang>
Vector3d.Dot(surfaceVelocity.normalized, forward) is the dot product of the surface velocity and vessel-forward vectors
<awang>
aka how much of your surface velocity is actually pointing vessel-forward
<awang>
Er, made a mistake
<awang>
dot product of the surface velocity *direction* and vessel-forward vector
<awang>
So what proportion of your surface velocity is actually going forwards
<awang>
1 - that is the proportion of your surface velocity that is not going forwards
<awang>
So multiplying that by dt * acceleration gets you dv spent not going forwards
<ProjectThoth>
Ahh.
<ProjectThoth>
awang: So if I was dead-reckoning velocity, would the true acceleration involve subtracting gravity losses out of it?
<BadRocketsCo>
Guys, does lqdoxygen and the sort evaporate when you're not focused on the vessel in question?
<ProjectThoth>
BadRocketsCo: Tempted to say "yes."
<BadRocketsCo>
Alright
<awang>
ProjectThoth: What do you mean by dead-reckoning velocity?
<ProjectThoth>
awang: Using kinematics and acceleration to predict burnout velocity along the velocity vector.
<awang>
Uhhh
<awang>
Maybe?
<awang>
You'd want to integrate all accelerations over burn time
<awang>
Since acceleration is a vector, you can integrate them separately, then add them together after
<ProjectThoth>
Yeah, I have a model trajectory and all that.
<awang>
So yeah, I think gravity losses would be subtracted out of that?
<ProjectThoth>
Though I'm doing it the difficult way because I'm bad at calculus.
<awang>
What's the difficult way?
<ProjectThoth>
Doing it in 10-second intervals algebraically.
<awang>
...Isn't that calculus with really large timesteps?
<awang>
Also, I just realized
<awang>
Do gravity turns work on airless worlds if you don't have any kind of thrust vectoring or such?
<awang>
On Earth, aerodynamic forces provide torque for you
<lamont>
the idea of a gravity turn though is to have a nearly zero lift ascent
<awang>
Right
<awang>
But something has to provide the torque to turn the rocket, right?
<lamont>
gravity does
<ProjectThoth>
awang: Yes, but I'm bad at calculus.
<awang>
Both gravity and engine thrust effectively act through the CoM though, right?
<lamont>
in a “perfect” gravity turn you would have no AoA to the atmosphere and it would not be providing any torque
<awang>
So they can't provide any torque?
<lamont>
torque is wrong, its force which is not aligned with the velocity vector
<lamont>
the same force that causes you to swing around in a circular orbit is the same force that causes a gravity turn to curve — gravity
<awang>
That doesn't necessarily change your orientation though, right?
<awang>
I see how the velocity vector changes, that falls out easily from vector addition
<awang>
Wait
<lamont>
yeah you need some kind of control authority over orientation