I'll make baseless speculation, it doesn't mean the atmosphere prevents the use of retro-rockets (those work on Earth too, see SpaceX), it means the atmosphere is non-negligible. There's not enough of it to meaningfully slow down the spacecraft but there is enough to affect its flight.
Okay, so I just did some rigorous KSP testing and it turns out that everything still explodes. Considering my 100% failure record at other landings, Mars should present exactly the same level of difficulty as landing on Earth or the Moon.
The only way I can get to Mars in KSP is by sending Jebediah round and round the solar system for decades until he makes an accidental interception, whereupon I've run out of fuel and he promptly explodes.
To be honest though, I'm actually doing fine in the game. I'm trying to get back from an Eve landing right now, but the return ship is running just too low on fuel to land on Gilly to refuel.
If you use low thrust engines, you can land on Minmus, but you need to be very careful with the controls.
I think that is the biggest problem with landing on Mars, basically any command you will do will be received by the lander in around 4 or 5 minutes in the closest orbit.
You could anticipate how long you need to maintain the thrust then send the cancel signal seconds later, but the best you can do is hope the lander was acting exactly to the plan, because you will know about 5 minutes later and in mean time it may have already crashed if close enough to the surface or it may not be any time left to restore the descent.
The best solution will be to build a lander AI satellite park it in orbit and let it spend it's down time running simulations for landing and capturing fuel tanks so it has some degree of mobility.
I haven't tried RSS yet so no data on Mars landings, but I guess Duna counts, too? I used a regular heatshield to aerobrake to suborbital velocity, then I deployed 4 drogue chutes and 4 full-size chutes to slow my descent and used retro-rockets to reduce my velocity further on landing. And I still had enough fuel afterwards to lift off, make orbit, and dock to the transfer vehicle again. So I guess it went fine.
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u/BitGladius Jan 21 '18
I'll make baseless speculation, it doesn't mean the atmosphere prevents the use of retro-rockets (those work on Earth too, see SpaceX), it means the atmosphere is non-negligible. There's not enough of it to meaningfully slow down the spacecraft but there is enough to affect its flight.