|
|
|
|
|
|
by cruffle_duffle
639 days ago
|
|
|
Jesus the orbital injection alone wasn’t something I would have thought about. We rely a lot on the atmosphere to break our probes. Without that you need to burn just as much fuel slowing down as you did speeding up. Well, actually that isn’t true because your mass is way different so your fuel requirements are much, much less than that initial launch but still a non trivial amount. I’m not a space probe engineer but I sometimes wonder if we go overboard on specialized compute hardware. I kinda wonder if that made more sense “back in the day”…. Ingenuity only rad hardened microchip is its flight controller. The rest is commercial off the shelf “normal hardware”. I dunno… all I know is most people including myself ask the same questions as the parent. What the hell are we waiting for? Send some shit over there! Let’s do this. |
|
|
Yes and no. The atmosphere on Mars is a great example of the worst of both worlds. It's actually worse than having no atmosphere at all. It's not enough for aero braking. But it's enough to blow corrosive dust all over your solar panels and instruments and generally make your life miserable.
Of course, aero braking works exceptionally well on Venus but it has... other issues.
It did help on Titan though with the Cassini-Huygens probe.
> Without that you need to burn just as much fuel slowing down as you did speeding up
Not really. It's... complicated. If you were going between two points in the same inertial frame of reference then yes you need equal delta-V to slow down at the other end but, as you point out, that takes less fuel because your weight is lower (although part of your initial delta-V comes from the launch vehicle you disposed of).
But the EArth is going around the Sun at ~30km/s. Jupiter is going around ~15km/s. Europa is going around Jupiter at ~13km/s. So we have to speed up to escape EArth's orbit (around the Sun) and the EArth's gravityh well but also slow down to match Jupiter's velocity and also avoid speeding up too much as Jupiter's gravity well captures you.
But the lower orbital speeds of the outer planets is why we have never done an orbital insertion on Uranus or Neptune. This distance and delta-V requirements put flight times at like 10-30 years, depending. Heck, we haven't even done a flyby of each and that was back in the 1980s. Saturn is kinda of our practical limit for orbital insertion currently. And that's expensive and takes a long time.
But Europa having an icy surface is just a huge complication. Even if you do a burn to slow down, what's the heat on those thrusters going to do once you land? Is it going to melt ice and then you immediately drown? How thick is the ice? I don't mean overall thickness. I mean there may be crevasses and such. Just look at how dangerous it is to walk across glaciers.
How will you get traction on ice in relatively low gravity?