Landing on bodies with no atmosphere

[heyo]

I know we did this during the Apollo era, which was before my time, but at least I know it can be done.<br /><br />Lately we've had great success with robotic probes landing on Mars and Titan. All of our landings in my era that I have watched, though, have been the atmospheric entry/heat sheild/parachute type EDLs. <br /><br />Seems to me the presence of an atmposphere greatly reduces the amount of additional fuel needed to decellerate/de-orbit the craft, and makes the landing much easier.<br /><br />I wonder how much harder it will be when we want to go places like Io, Triton, Europa, Callisto, etc., ...places with no appreciable atmposphere to speak of. <br /><br />I suppose we'll have to use reverse thrust to slow way way down and then use retro-rockets to slow down and land.<br /><br />This seems extremely difficult for a remote robotic probe that will have to do it all autonomously. It could tip over under hover/retro power and wreck itself, it could have too much horizontal velocity and wreck itself, it could hit the ground to fast and wreck itself, etc...<br /><br />Can we do it without crashing?<br /><br />Heyo

 

[najab]

The Vikings did it succesfully - they did use a heat shield and parachutes, but the landing was made using 'rocket power'. The Surveyor and Luna probes did it succesfully on the Moon, so there's no fundamentally new techology to be developed.

 

[fangsheath]

People underestimate the capabilities of computers as pilots. Even the primitive Apollo LEM computers were capable of performing most of the descent, and did so. <br /><br />Creating algorithms for power descent really is not all that complicated. You need radar inputs to give you your vertical velocity and a guidance system to keep track of your attitude and trajectory. From these inputs it is simply a matter of calculating a descent trajectory and vectoring and throttling your descent engine. It is actually only a little more complicated than that - you have to account for the decreasing vehicle mass as propellant is consumed, and so on. The really tricky bit is at the end when you have to take into account the unevenness of the surface. It is all quite doable, and every year that passes advances the technology further. <br /><br />The Orbiter space flight simulator is a pretty good, and fun, way to learn about such things. And best of all - it's free!<br /><br />www.orbitersim.com

 

[heyo]

Yeah, Orbiter is a lot of fun. I'm just now able to get into orbit, then get to the moon and orbit the moon (thought now in the most graceful manner) and maybe get back to Earth orbit if I'm lucky. I am going to try to go to Mars soon.<br /><br />Haven't tried a landing though, I will have to give that a shot.<br /><br />Heyo

 

[CalliArcale]

The most recent robotic landing on a body without an atmosphere was actually in 2001. The NEAR-Shoemaker spacecraft, never designed for landing, touched gently down on the surface of asteroid 433 Eros, becoming the first spacecraft ever to land on an asteroid. It was quite a remarkable acheivement, as the spacecraft lacked the features normally associated with landers (like landing gear!). They basically lowed the orbit periodically and then carefully planned out its final descent so that it gently touched down at 3 meters/second in the weak gravity of Eros.<br /><br />Near Earth Asteroid Rendezvous Mission Web Site <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[chew_on_this]

According to the scientific community is more like it.

 

[najab]

><i>Well, according to many around here, there are NO bodies to speak of known, with NO atmospheres, so that's an end to this thread.</i><p><br />Actually, steve, if you read the initial post in the thread the question is "I wonder how much harder it will be when we want to go places like Io, Triton, Europa, Callisto, etc., ...places with no appreciable atmposphere to speak of." - the key word here being appreciable. For purposes of landing (or flying helicopters) the thin atmosphere of the moons listed can be ignored.</p>

 

[vogon13]

Soviet technology was up to the task in the sixties, on the moon (Luna 3, I believe). Carrying rocket fuel to destination is annoying, though, heavy, complicated plumbing, chance of it freezing or leaking away. Ion propulsion concepts not robust enough for landing on anything very big at all. <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[najab]

><i>Actually, If YOU had bothered to read the actual, real existing, proveable "Title' of this thread.</i><p>Ahh...you just read the title of a thread and respond. That explains a lot. Personally I put more weight on the 180+ words of the actual post than the 40 characters or so allowed for the title, but that's just my personal preference.</p>