Lunar Slingshot Maglev: NASA's Energy Savings for Mars & Beyond

[darkdave3000]

TL;DR

The moon is actually a giant catapult from a certain point of view.

Has NASA considered building a maglev on the moon so we can use the lunar mass and momentum to gain higher energy savings for missions to Mars and beyond?

A spacecraft can be catapulted toward the destination with its rocket engines off and only turn them back on to course correct or slow down.

Furthermore it can be used to slow down spacecraft in low lunar orbit thus more energy savings for landers. Yes it will have to be precise landing but with computer guidance it can be done.

I would orient the rail from West to East along the equator of the moon so that our targets for outbound shoots are in a trajectory similar to if the moon was the rock on a sling being swung anti clockwise from the point of view of a northern observe . This will take capture momentum from the angular spin of the Moon has as well as it's orbit. The rail would need to be at least 100km long or more.

On Earth this isn’t an option but the moon is a near vacuum.

 

[anorlunda]

How difficult is it to build a Rail Gun on the Moon?​

https://forum.nasaspaceflight.com/index.php?topic=56504.40

 

[berkeman]

[Mentor Note: Thread prefix level changed from "A" = Graduate school levle to "I" = Intermediate undergraduate level]

 

[russ_watters]

I don't see that a maglev has anything to do with a lunar slingshot.... but I'm envisioning a spaceship trying to engage with a rail at high speed without crashing...

So, what purpose does this serve that a normal lunar gravitational slingshot wouldn't already do? And is there much actual benefit to a lunar gravitational slingshot? I don't think I've heard of it being done (Earth, yes though).

@darkdave3000 some advice: PF is a serious science site. This and your prior thread don't appear very serious, which is why the last one didn't go well. To make this and future threads go better, you'll need to put more effort into making them serious and not just hand-wavey.

 

[Rive]

The rail would need to be at least 100km long or more.

Every effort needs to have the promise of some gains to justify it.

It would require quite an interplanetary traffic to justify the building of such structure ...

I'm afraid we are not even close to just being able to fairly assess such project.

 

[Vanadium 50]

I don't see that a maglev has anything to do with a lunar slingshot

This thread seems to mix three ideas - maglev, a mass driiver, and gravity assiste ("slingshot"). Based on the OPs posting history, I think he believes that the path to discovery/invention is through words, not numbers. But as @Rive points out, numbers matter.

I haven't confirmed the 100 km number, as it depends on where in the solar system you want to go, whether you are willing to launch fuel, and how much force your space probe is able to tolerate, but the scale is surely kilometers and not meters.

The issue I see is that to launch something from the moon you need to get it to the moon. The energetics in earth-moon-destination are only a few percent different from earth-destination. At best. You almost certainly lose any gains because of inefficiencies. And "lets just build the probes on the moon" isn't so simple. There's a big difference between a rock with silicon in it and a CPU.

 

[darkdave3000]

I intended to post the numbers when I get around to it. What is the expected response rate in forums these days? Because I don't live on forums, I post something I go away for a week and add the numbers later based on response.

 

[darkdave3000]

I am actually working on a spreadsheet but it isnt complete yet and I dont want to post half finished work, but from what i can tell you about it is that it can get us numbers of up to 24km/s if the railgun/maglev wraped 360 deg around the Moon, but I don't think this will be practical because even with 3g acceleration it will end up after 1 revolution around the Moon with about 30g of centrifugal/centripetal forces pulling the spacecraft away from the lunar surface and this it self while great for non living payload would not work for human astronauts.

However even a much shorter rail length say 100-200km would already provide huge energy savings, I have not finished my spreadsheet yet and I'll post the results of that much shorter rail length here when is complete. But you should get the idea, a spacecraft being flung toward Mars at say 15km/s can spend most of it's fuel to just decelerate and thus create artificial gravity a very very important need in space.

 

[Vanadium 50]

I am actually working on a spreadsheet

I have a truly remarkable proof that unfortunately does not fit in the margins of this book.

 

[berkeman]

I have a truly remarkable proof that unfortunately does not fit in the margins of this book.

LOL. Quiz Question -- What movie is that from? Oh, wait...