Horizontal Munar Landing: Is it possible?

[Raelsmar]

As the thread title muses, I wonder if it is possible to use the wheeled landing gear to perform a horizontal landing on the Mun. The problem I can most easily see is the lack of atmospheric drag and an increasing sinkrate. The positioning of the RCS thrusters on my craft make it nearly impossible to counter vertical movement. Is there a way of making one\'s entry trajectory shallow enough to allow for a safe landing in this manner? Any help or suggestions would be greatly appreciated.

[togfox]

You would be going VERY VERY fast, such that I\'d consider this impossible.

[Bluejayek]

I see no reason why you couldnt turn horizontal, kll velocity mostly with rcs, then land with wheels. The surface doesnt model the giant dustcraters and such that might screw you up, so it should work.

[vexx32]

Theoretically yes. Practically, it\'s very difficult. I would suggest attempting to build a craft that can basically kill the vertical motion, since unless you\'re unlucky enough to fly into the side of a very steep hill or cliff, the horizontal motion won\'t be the death of you if you have wheels. The only other problem is being oriented in the direction of motion. Again, perfectly possible.

[matmilne]

assuming that you simply lose the periapsis and land in a shallow curve somewhere inside a crater you should be OK, the key is not exploding, suitable parts with high crash tolerances and low explosion potential are critical.

On my first successful lunar landing, the ship landed vertically, fell over, and slid down a crater wall without exploding. Had to take off again with the ship on its side at the bottom, quite fun. (sadly i time-warped on the return and de materialised in the middle of kerbin with the loss of all hands)

[DomAzaris1996]

Only way I have is when I made a rover, landed vertically then tipped over with RcS...

I never have got a spaceplane in orbit I\'m only really good with rockets haha

[Trekkin]

It\'s possible theoretically, but there is one very large problem with relative velocities. Put simply, the minimum orbital velocity for the Mun, even at dangerously low altitudes, is nowhere near as low as the maximum velocity wheeled landing gear can take on impact.

The game, then, is to rapidly transition from the one state of affairs, that of being in orbit with ludicrously low periapsis, to the other, that being going very slowly. You\'ve also got to do it above a long, flat stretch of Mun to act as a landing strip and recieve your craft without a bump collapsing your gear or a mountain in the way of your orbit.

Given that, I\'d use very high-thrust retros--possibly, for a sufficiently large lander design, SRBs, or large banks of linear RCS at minimum. Fly straight and level just over the runway, engage them, jettison them relatively soon after, and then use RCS to control the craft down. It\'s nothing I\'d want to try without computer guidance, though.

[Raelsmar]

I\'ve tried it several times since the original post, and I must say, it\'s nearly impossible to do this (at least with my questionable lander design). I\'ve had somewhat more success using the medium thrusters as landing gear (although the 7 impact tolerance essentially guarantees they will snap off no matter how slow you descend) but I\'m entirely unable to leave the munar surface.

I\'ve even resorted to placing several sets of landing gear in radial symmetry in an attempt to reduce the need for exact orientation upon impact, but the time it takes to change from vertical to horizontal landing orientation leads to an increase of vertical speed followed by an explosive splat onto the surface.

If anyone has any design alteration suggestions, I would be happy to adopt them, as I\'ve grown somewhat attached to my SpaceStar and don\'t want to entirely scrap the design.

[Trekkin]

How exactly are you trying to land this? I would think you would try not to change landing orientation at all.

[Markus Reese]

The way I do it is I build the rocket in the SPH, for up to the landing phase, then I copy the save file for the craft into the VAB. For landing controls, I actually use rotated thrusters. While I land in the horizontal profile, I still use vertical ones. The other way as a straight plane is to use vertical thrust til near surface than pitch forward. It is difficult and causes a combined foward motion with vertical to pitch yourself down. Either way, it pretty much has a vertical component

[Wayward]

The best I was able to do, was to land vertical and 'tilt' it off....a bit stressful, but it works....

[bdawg]

The best I was able to do, was to land vertical and 'tilt' it off....a bit stressful, but it works....

This worked best for me as well. I mean technically, it\'s a vertical landing, but the conditions kind of demand it. :-[

[Torpedo423]

I did it by accident, had enough fuel left for the main engines on the rocket so i just burned till i made it down to about 15m/s then detached the rover without trying to land and it landed just like a plane

[Trekkin]

I\'ve been trying this. Low PE landings, using a periapsis at 0 and an apoapsis at like 10 km. If one dodges the mountains, it\'s tantalizingly doable; I just keep overusing my retros and going back the other way.

Okay, I finally got it! You need a LOT of SRBs as retros, and you start deorbit burning at about 1500-2000 m or so, until your surface velocity and altitude are both near zero. It\'s tricky as heck, though, and lots of RCS helps. That said it does get you on the ground without an orientation change, albeit with enough velocity that not breaking landing gear is insanely hard.

[Khrissetti]

perhaps being ignorant here, but can\'t you just turn your spaceplane around and land backwards, if you\'re having a problem killing the speed?

[Mikemc]

One of my randomly orbiting spacecraft that are strewn about the solar system recently came very close to Mun. It was traveling in the same direction, so I do not see how this would not be possible. I\'ve always imagined it to be like in Mass Effect where you launch your rover towards it then fire some jets at the last moment to slow it down.. like the bungee cord on an aircraft carrier .

[vexx32]

Well, for a start, it IS possible, just extremely difficult. Also, ideally you want to be cutting vertical velocity at just the right moment to have zero velocity at the exact moment you touch the ground. Now, that isn\'t humanly possible intentionally, so you\'re going to have to waste a fair bit of fuel keep vertical velocity low (preferably around 100-200m/s above 10km and less than 100m/s below that, going down to 30m/s under 5km) so you can stop quickly in case you land on a high mountain, in which case the altimeter will be well into a few thousand metres by the time you touch the ground. Also, if you land going up a hill you ahve a much higher chance of crashing. A well-designed rover is also a necessity.

[olex]

I did a wheels-down spaceplane landing on the Mun yesterday. Screenshots:

Landing sequence: powered descent on the rocket engine up until a meter or so above surface, burst of throttle to float momentarily, flip wheels down with about 45° nose up, power up a bit, and land carrying some forward speed. Stop with wheel brakes.

I also saw a Youtube video where vertical RCS was used for the final touchdown after flipping the plane horizontal.

[Fortunateson1969]

Are you trying to win my challenge?

http://kerbalspaceprogram.com/forum/index.php?topic=16313.0

I point away from the surface and slow my Vert Speed to about 10m/s. Then, based on my appx of how high up I really am (AGL) I turn prograde(ish, really more like my desired approach angle) and fire the retros on the front. I have a whole mess of landing gear on the bottom and still haven\'t gotten it. The terrain gets me every time.