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Sat contracts on other planets question


Biggen
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So I've been mostly doing sat contracts recently trying to get better at using nodes.  I took a contract up for Eve and got my probe there successfully.  I thought I could aerocapture the probe but that turned out to be a HUGE mistake as the probe basically begins to explode at around 81KM with no airspeed even being bled off yet.  My craft was still accelerating while disintegrating.  I'm not sure I understand the physics of this, however.  How can the atmosphere generate enough heat due to friction to explode a ship but not slow it down??

 Anyway, back on topic, I ended up reloading and getting into orbit with a regular retroburn.  After I was in a parking orbit I was off 45 degrees from the inclination needed for the sat contract.  It's a good thing I brought a ton of fuel as I still had ~2500m/s delta v in the tank after the parking orbit because it took another ~2300m/s to adjust my orbit at the AN/DN to get to the correct inclination to satisfy the contract.

So my question is this, how can I adjust to the proper inclination of the sat contract orbit before I get into parking orbit of the planet?  I fiddled around with attempting to eyeball it when I was doing my mid-course burn to Eve, but I couldn't get my orbit to cooperate with the required sat contract orbit.  It seems that the orbit bends "funny" and I can't get both the beginning/ending SOI "legs" to wrap the way I need it to during a mid-course burn.

Surely there is a way to do this BEFORE getting into orbit of a planet.

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33 minutes ago, Biggen said:

So I've been mostly doing sat contracts recently trying to get better at using nodes.  I took a contract up for Eve and got my probe there successfully.  I thought I could aerocapture the probe but that turned out to be a HUGE mistake as the probe basically begins to explode at around 81KM with no airspeed even being bled off yet.  My craft was still accelerating while disintegrating.  I'm not sure I understand the physics of this, however.  How can the atmosphere generate enough heat due to friction to explode a ship but not slow it down??

Because slowing down takes time, and cooling off takes time, and heating can happen very fast. If your ship takes on heat slowly, and has time to cool itself, then it will slow down. If your ship takes on heat faster than it can cool itself, kaboom.

33 minutes ago, Biggen said:

So my question is this, how can I adjust to the proper inclination of the sat contract orbit before I get into parking orbit of the planet?  I fiddled around with attempting to eyeball it when I was doing my mid-course burn to Eve, but I couldn't get my orbit to cooperate with the required sat contract orbit.  It seems that the orbit bends "funny" and I can't get both the beginning/ending SOI "legs" to wrap the way I need it to during a mid-course burn.

Surely there is a way to do this BEFORE getting into orbit of a planet.

No. Your incoming path defines a plane. Your desired orbit defines another plane. You can minimize the difference between these two planes by making that difference perpendicular to your direction of travel, but you can't make it go away (unless you got lucky and the perpendicular difference was zero to begin with). So the best you can do is to minimize that difference at your midpoint correction -- and when you do your capture burn, leave your Ap really really high and do your plane adjustment at whichever node is at the higher altitude.

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Yeah,  I would budget a lot of delta v for Eve plane changes.   Fortunately,  if you have a light payload,  this is pretty doable with staging.    You could also consider an ion final stage.   They work well in Eve's strong sunlight and will get you tons of delta v.  

Another option is a heat shield to help aerobrake.

Edited by Aegolius13
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You can't match planes while inbound (unless you're really lucky) but you CAN adjust so your periapsis, and thus best capture burn, will be at AN or DN.  After that, just capture to an eccentric orbit, adjust plane at apoapsis (and thus the other AN/DN) and bring your orbit to match.

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Thanks guys.  I was coming into Eve around ~4000m/s when I hit the upper atmosphere.  I tried going in retrograde, but the engine couldn't handle the heat.  I then did an attempt prograde and the AE-FF2 fairing took the heat better but it was redlining and I didn't bleed of enough speed to make a difference anyway.  I was packing 4 active small radiators and they didn't do jack to stop the heating.  They still exploded (actually the fuel tank they were sitting on) around 15% cooling capacity.

If I did Eve again, I would maybe burn half retro and maybe half radial.  I would think that would help bleed off speed while keeping the Pe at approximately the same height.  Although, end in the end, I don't know if it makes any difference as far as delta v efficiency doing something like this way than just doing a full retro burn at Pe to get a capture.

I'll also remember to get a really high capture orbit next time and do the normal/antinormal burn at their highest point to conserve fuel.

I like these sat contracts.  I'm flinging RA-100's all over the solar system every time I do a sat contract so hopefully that will help me with a stable relay network down the line.  It's also teaching me better maneuver nodes and encounter techniques which is also a plus.

Edited by Biggen
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I'm pretty sure that in order to do this, you would need to be entering the planet's SOI while already in the same plane as the target orbit, which in most cases WON'T be possible since the inclination you enter from will be determined by where you're coming from.  The best you can do would probably be to get as low a Pe as possible and do a capture burn to a highly elliptical orbit with the Ap at the ascending/descending node, then correct your inclination there, and finally adjust your Ap and Pe to the desired heights.

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5 hours ago, bewing said:

Because slowing down takes time, and cooling off takes time, and heating can happen very fast. If your ship takes on heat slowly, and has time to cool itself, then it will slow down. If your ship takes on heat faster than it can cool itself, kaboom.

No. Your incoming path defines a plane. Your desired orbit defines another plane. You can minimize the difference between these two planes by making that difference perpendicular to your direction of travel, but you can't make it go away (unless you got lucky and the perpendicular difference was zero to begin with). So the best you can do is to minimize that difference at your midpoint correction -- and when you do your capture burn, leave your Ap really really high and do your plane adjustment at whichever node is at the higher altitude.

Actually plane correction optimization is frequently different than that. If you can cause the desired and actual orbital planes to intersect at Pe during mid course correction you can include plane alignment during capture burn. Low to moderate inclination corrections are cheaper as a normal component of a already large capture burn than a separate normal burn at higher altitude thanks to the nonlinear nature of vector addition. Getting that Pe on the intersection at mid course burn only requires prograde and normal vector adjustments. Throw in radial though and you now control insertion time. At this point you can also rendevous on capture moderately efficently!

The only challenge is polar orbits where you want a highly different AoP. That relies on rendevous time more than inclination. However the only time I've cared about AoP is satillite constellation construction.

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