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Horizontal landing on other planets

Posted by: Ekkehard Augustin - Wed Oct 20, 2004 10:32 am
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Horizontal landing on other planets 
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Post    Posted on: Tue Nov 02, 2004 5:00 pm
If there is very little gravity and little atmosphere, couldn't the landler simply fly from space towards the planet at a very slow speed?

I often pondered why they don't take the Space Shuttle out to the moon and land it horizontally on skids or similar.

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Post    Posted on: Tue Nov 02, 2004 5:16 pm
roygrif wrote:
If there is very little gravity and little atmosphere, couldn't the landler simply fly from space towards the planet at a very slow speed?


That is exactly what the NEAR mission did. It just approached the asteroid very slowly and "landed". For a bigger planet you can't go slow all the way down without something (parachute, wings, rocket) to keep you from accelerating under the planet's gravity as you "fall". And unless you fly all the way from Earth really slowly you have to slow down some way, and atmospheric drag is almost free, except for the cost (that is weight) of the heat shield.


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Post    Posted on: Wed Nov 03, 2004 11:48 am
Hello, campbelp2002,

having a vehicle that is able to land at and to launch from each planet safe and secure could save a lot of financial ressources and costs. It could be carried to each planet by a carrier vehicle that does never land.

SS1 is reusable on earth - it could be interesting to have a vehicle that is reusable at each planet and not on earth only. Regardless wether it is manned or unmanned.

I suppose that SS1 could be modified to be able to land on water or at snow. If it could be modified to be used landing and launching at/from Mars as well as at/frim Earth then it would be a solution for the manned Mars mission. Another possibility would be to modify it to an unmanned robt travelling from planet to planet and land at that planets. I'm sure there are break-even-points at which this becomes economical advantageous.

That are the reasons why I wrote my initial post. If a way could be found by which that is possible the costs could be calculated and the break-even-points could be found - then there would be a basis for decisions.



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Post    Posted on: Wed Nov 03, 2004 2:30 pm
I wasn't considering reusability, that does make a difference.

In the case of the moon, since there is no atmosphere the only solution is vertical rocket landing, like Apollo or Armadillo. The shuttle's or SS1's wings would just be useless weight.

For Mars the atmosphere is so thin that you would need extremely large wings; too large to be practical. For Venus or Titan or the gas giant planets wings would work, but who really wants to go there? (How I miss the old days when science fiction considered Venus and Mars to be similar enough to Earth the we could breathe the air!)

In all the above cases you either need a nuclear rocket or the ability to make propellant at the landing site to get reusability. It has been pointed out that transatlantic air travel would not be economically viable if you could not refuel at both ends of the trip.

For asteroids, you don't even need landing gear, you can just slowly drift to the surface. And almost no rocket power is needed to take off again. In fact, since the low gravity of asteroids makes landing and takeoff so easy, a round trip from Earth to Moon landing and back actually takes more rocket power than a round trip to a near Earth asteroid.


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Post    Posted on: Wed Nov 03, 2004 3:02 pm
From my point of view horizontal landing at moon is possible by combination of vertical braking rockets with horizontal braking rockets.

Reusability at each planet is meaning that for earth wings are required but for moon could be removed - for example. Might be a question of modularization which I tried to discuss much earlier this year.

Going to Titan might be interesting for economical and industrial reasons - we should wait for the first results to be delivered by Huygens. Scientists seem to be speculating wether Titan has a thick layer of organic material. If it has really that layer then this could be of meaning for colonizing other planets.

Venus is interesting not only because of the possibility of life in the upper atmosphere - in principle that upper atmosphere could be colonized a little bit. Temperatures are normal there - entry by SS1-like vehicles may make sense then. Colonization could be based on stations like JP Aerospace's Dark Sky Station that they want to install at 140,000 feet altitude.



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Post    Posted on: Wed Nov 03, 2004 4:55 pm
Probably horizontal landing on the moon is possible, but I can't see any advantage to it. In the end you need to stop, the only question is do you stop above the surface and land vertically, or do you land with some horizontal velocity and slow down while travelling over the surface. The advantage of horizontal landing for aircraft is because they need their wings to travel in the atmosphere anyway, the horizontal landing is "free", except for the cost of building the airport. That cost is so high that a lot of effort has gone into making vertical landing aircraft, such as helicopter, tilt rotor and vectored thrust jet aircraft. So far the technology just does not work well enough and it is still easier to build airports.

For the moon the opposite problem exists. Wings are useless due to lack of atmosphere and horizontal motion is easily cancelled out completely before touchdown by the landing rockets.

As for reusability, the Apollo LM could probably have taken off without leaving half of it on the surface if it could be refueled on the ground. I can foresee a future moon hotel where large LM type vehicles land, refuel and take off reusably, but they would do so vertically I think. And such a vehicle would not land on Earth but instead transfer payload to a winged vehicle for Earth landing. And if they do, I want to go!


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Post    Posted on: Thu Nov 04, 2004 8:40 am
Horizontal landing at moon too might be safer than vertical landing. Vertical landing could be compared to direct colliding to an impact. Stronger forces are effecting the vehicle compared to horizontal landing.

Wings are useless at moon yes - but not at earth. So a winged vehicle might launch from earth because the wings are of use at earth. It might take them to the moon then were they are useless but at or after reentry into earthian atmosphere the wings are of use again..

An alternative would be removal of the wings once the vehicle is in space and on the way to the moon and to move the wings onto the vehicle again after it's back from the moon and about to reenter.



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Post    Posted on: Sat Feb 07, 2009 9:02 am
What about satellites or stations the spacecraft to be landed horizintally docks to? There it could be attached to tethers. Then the tethers are rolled down to the surface.

At a certain proximity to the surface the spacecraft could fire deceleration thrusters horizontally and be released from the tethers.

Since the tethers will have provided a slow descent the remaining distance will not be gone as fast as without the tethers. So if at all retro rockets are needed they will have to fire for a shorter period and perhaps not that strong.

This way a spacecraft perhaps might land horizontally on the Moon too.



What about that?



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