Are lunar landings without chemical rockets possible?

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Discussion Overview

The discussion revolves around the feasibility of lunar landings without the use of chemical rockets, exploring various theoretical and practical approaches to achieving a successful landing on the moon's surface. Participants consider the implications of different landing definitions and the challenges posed by the moon's environment.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that without rockets, a satellite would crash upon landing due to high speeds, proposing the idea of using airbags to cushion the landing and suggesting a downward slope for a softer touchdown.
  • Another participant counters that the accelerations involved in using an airbag would be unmanageable, citing extreme negative accelerations and the need for materials capable of withstanding the lunar surface's abrasiveness.
  • A different perspective is introduced regarding the definition of a landing, indicating that while hitting the surface without rockets may be straightforward, ensuring the device remains functional post-landing complicates the discussion.
  • Participants note the absence of an atmosphere on the moon, which contrasts with Mars and affects energy dissipation during landing.
  • One participant mentions a Swedish rocket that utilized ion engines, suggesting that while currently weak, such technology might be developed further to facilitate lunar landings in the future.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of landing without rockets, with some focusing on the practicality of various methods and others emphasizing the challenges posed by the lunar environment. The discussion remains unresolved regarding the viability of alternative landing technologies.

Contextual Notes

Participants highlight the significant challenges related to landing speeds, material limitations, and the definition of a successful landing, which may depend on the intended functionality of the landing device.

guss
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If a satellite tries to land on the moon without rockets to counter the force of gravity, it comes in too fast and crashes into the surface destroying itself. A satellite would be orbiting at approximately 1.8 km/s or so at a 50km altitude, and come in for landing from that height which would speed it up an additional .4 km/s. All in all we are probably talking 1.2km/s in the horizontal direction and 400 m/s in the vertical direction upon touchdown. It would I was thinking there may be some type of airbag that could deploy, and allow it to roll on the surface which would slow it down in the vertical direction. Maybe have it land on a downward slope for a bit of a softer landing?

Just something interesting I was thinking of. Any ideas?
 
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It might help if you thought of the problem from a practical standpoint. You're talking about trying to bring something from 4300 km/hr in the horizontal, and 1400 km/hr in the vertical, to a stop. There's just no way to do that with an airbag and keep the accelerations reasonable.

Taking into account just the vertical speed, if we assume your airbag is 10m thick (that sounds like a pretty big airbag), you're talking an acceleration of -8,000 m/s^2 (-816g), not even including the 182 rpm spin rate that would be induced from impacting the surface at 4300 km/s. Your airbag would also have to be made out of material that is tough enough to handle hitting the very abrasive lunar surface (basically ground silica glass) at that speed, probably not possible with any existing technology.
 
The answer to this question relies heavily on how you define a landing. In general terms a lunar landing without a chemical rocket is very easy to do as long as you are aimed at the surface and you hit said surface. If you require the landing device/object to be usable afterwards then this conversation changes completely ;)
 
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Yes landing... in one piece.. and functional.
 
No atmosphere to dissipate any energy like on Mars.
 
There was a swedish rocket that used ion engines. Terribly weak engines they said. but in the future perhaps those would be able to counter the gravity enough to make a landing.
 

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