Author Topic: Can we propel a small moon?  (Read 3163 times)

Can we propel a small moon?
« on: 12/09/2021 06:33 am »
Is it possible to attach a nuclear spacecraft on a Demios [Moon of Mars] which is 6.2 KM in size.
and use it as an Interplanetary Space Ship A.K.A USS Enterprise?

If possible, why create fragile ISS instead of using Rocks as Space Stations and Space Vehicles???

Offline daedalus1

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Re: Can we propel a small moon?
« Reply #1 on: 12/09/2021 06:49 am »
It weighs 2 trillion tonnes.
Think about how you would change the velocity of that even by a few kilometers/hour.

Re: Can we propel a small moon?
« Reply #2 on: 12/09/2021 07:02 am »
Yes, its a challenge. but Launching 2 Trillion Tonne Interplanetary Space Craft also is a Challenge.

1.Building such a huge space craft on Earth and launching is impossible
2.Building such a huge space craft in our Orbit also is a humongous challenge
3.It is also an equally challenging engineering to propel a super massive space rock

but why not try?

Offline Hobbes-22

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Re: Can we propel a small moon?
« Reply #3 on: 12/09/2021 07:12 am »
We don't need 1012 tons of material to build a viable interplanetary spacecraft. So the choice isn't between converting Deimos or launching 1012 tons, it's between converting Deimos and launching 103 tons - which is a billion times easier. 

Offline Welsh Dragon

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Re: Can we propel a small moon?
« Reply #4 on: 12/09/2021 07:19 am »
Can we propel a small moon? Yes. We can even propel a large moon. Stick an engine on the surface with a exhaust velocity larger than escape velocity and you'll propel it. Can we propel it by more than a few nanometres per second* with existing technology? No.

* I have not done the maths, this implies an infinitesimally small but non-zero amount.

Offline daedalus1

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Re: Can we propel a small moon?
« Reply #5 on: 12/09/2021 07:51 am »
Yes, its a challenge. but Launching 2 Trillion Tonne Interplanetary Space Craft also is a Challenge.

1.Building such a huge space craft on Earth and launching is impossible
2.Building such a huge space craft in our Orbit also is a humongous challenge
3.It is also an equally challenging engineering to propel a super massive space rock

but why not try?

You haven't really thought about it .
Nearly all that 2 trillion tonnes is material that is pointless for an interstellar flight. It wouldn't be attempted for that reason alone. Then you've got all the other reasons not to, like designing an engine big enough to take it out of Mars orbit let alone Solar orbit. And please don't just say a nuclear rocket as if that is the answer to interstellar flight.

Re: Can we propel a small moon?
« Reply #6 on: 12/09/2021 09:48 am »
Now I can understand better.

Still more curious...

1.Why do you say, building an interplanetary vehicle made out of nuts and bolts are more robust and efficient than re-infocring space rocks and build habitable buildings on it?

2.why not use all the best propsulsion system we have ? [Nuclear + EMD + Plasma Drive + whatever] to move such a massive rock? [we dont need warp acceleration, as long as it can move slow enough for "interplanetary distance than interstellar distance" it can be manuvorable


-- Trying to understand Better --

Offline octavo

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Re: Can we propel a small moon?
« Reply #7 on: 12/09/2021 10:14 am »
Now I can understand better.

Still more curious...

1.Why do you say, building an interplanetary vehicle made out of nuts and bolts are more robust and efficient than re-infocring space rocks and build habitable buildings on it?

2.why not use all the best propsulsion system we have ? [Nuclear + EMD + Plasma Drive + whatever] to move such a massive rock? [we dont need warp acceleration, as long as it can move slow enough for "interplanetary distance than interstellar distance" it can be manuvorable


-- Trying to understand Better --

1. Mostly because nuts and bolts (or sheet metal and composites) are *much* lighter than stone and rocks. You can also manufacture things in convenient shapes, instead of having to blast holes in the rock first so you can start to build in it.

2. Because regardless of how good your propulsion is, it must throw something out the back of the engine in order to go forwards. That means that your fuel, even nuclear, is limited to some amount. The heavier your craft is, the more fuel you are going to need to move that craft. I do not think you understand how heavy even a small moon is.

Offline missinglink

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Re: Can we propel a small moon?
« Reply #8 on: 12/10/2021 07:23 am »
"Hotshot", a short story by science fiction writer Peter Watts, takes place aboard a large asteroid hurtling across the universe at a large fraction of the speed of light. It was launched from the solar system millenniae ago, its purpose is to install wormhole "junctions" whenever it passes close by a suitable star. Presumably the energy required to accelerate the asteroid was well, astronomical, but only something this massive can be expected to endure the erosion caused by countless collisions with particles of all sizes along the way.
Read it for free on the author's website: http://rifters.com/real/shorts/PeterWatts_Hotshot.pdf

Offline Hobbes-22

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Re: Can we propel a small moon?
« Reply #9 on: 12/10/2021 10:12 am »
Now I can understand better.

Still more curious...

1.Why do you say, building an interplanetary vehicle made out of nuts and bolts are more robust and efficient than re-infocring space rocks and build habitable buildings on it?

2.why not use all the best propsulsion system we have ? [Nuclear + EMD + Plasma Drive + whatever] to move such a massive rock? [we dont need warp acceleration, as long as it can move slow enough for "interplanetary distance than interstellar distance" it can be manuvorable


-- Trying to understand Better --

1. Small asteroids are often composed of loose rubble, not a solid chunk of rock. So before you can do anything with it, you have to encase the whole asteroid in concrete to keep it together. The material cost for that operation alone is astronomical.

2. the biggest problem of rocket propulsion is colloquially called the tyranny of the rocket equation. Basically, to get anywhere, most of the mass of your spacecraft must be fuel. That means the lighter your spaceship is, the easier it becomes to accelerate.
We have no engines that can move a 1012 ton mass at more than nanometers per second. Build a spaceship that's 109 times lighter, and those same engines now provide useful acceleration.

Offline AS_501

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Re: Can we propel a small moon?
« Reply #10 on: 12/11/2021 05:04 am »
The idea of propelling a small Solar System body brings to mind a NASA-Ames proposal to very gradually move the Earth away from the Sun using carefully controlled asteroids or comets. Quoting from June, 2001 edition of The Guardian, "The plan put forward by Dr. Greg Laughlin, and his colleagues Don Korycansky and Fred Adams, involves carefully directing a comet or asteroid so that it sweeps close past our planet and transfers some of its gravitational energy to Earth.  'Earth's orbital speed would increase as a result and we would move to a higher orbit away from the Sun,' Laughlin said."  The Moon would complicate this process to some degree, but would not be a show-stopper.

At the time, the proposal stirred controversy because it was seen by some as a solution to global warming.

Let's jump ahead 10 billion years and use this method to gradually move the Earth away from the Sun as it expands into a Red Giant.  Earth is not doomed after all!

Note:  Perhaps a future NSF member can start a thread about this in the Year 5,000,000,000 AD. :)


Launches attended:  Apollo 11, ASTP (@KSC, not Baikonur!), STS-41G, STS-125, EFT-1, Starlink G4-24, Artemis 1
Notable Spacecraft Observed:  Echo 1, Skylab/S-II, Salyuts 6&7, Mir Core/Complete, HST, ISS Zarya/Present, Columbia, Challenger, Discovery, Atlantis, Dragon Demo-2, Starlink G4-14 (8 hrs. post-launch), Tiangong

 

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