Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Magnetoplasma drive could make Mars transit take 39 days?

orbitalindex.com

Post reply on HN
Print view View original

41–50 of 90 posts

Re: Magnetoplasma drive could make Mars transit take 39 days?

#41

Post by skunkworker »

ashtonkem wrote: post #25
snake_plissken wrote: post #18

Some quick math: 32 miles per second (see one of their linked articles, https://www.spaceflightinsider.com/conferences/vasimr-plasma... ) is 155,200 miles per hour. Assume you accelerate at 21 MPH, which is about 1 g (100 KPH ~ 60 MPH, 100 KPH / 32.81 KPH/S^2 = 2.85 s, 60 MPH / 2.85 s). So at 1 g It takes you about 228 days to reach cruising speed, 2 g takes 114 days, 3 g 57 days. So I don't think this would not be u…

And remember that you have to bleed most of that speed off before entering orbit. Even with aerobraking most orbiters try to slow down to ~2km/s before hitting the atmosphere. Hitting the Martian atmosphere at 32miles per second wouldn't be an acceptable plan in KSP, let alone in real life.

If this existed I would expect it would do something similar to The Expanse where they "flip and burn" to slow down coming towards the target. On the plus side, your craft could have decent "gravity" for most of the whole trip.

Re: Magnetoplasma drive could make Mars transit take 39 days?

#42

Post by jessaustin »

avmich wrote: post #5
blakesterz wrote: post #2

"A massively scaled up version running at 200 MW could make the one-way transit to Mars in as little as 39 days, but generation of this amount of in-space energy isn’t currently anywhere near possible and would require both an advanced onboard nuclear reactor as well as super-efficient heat radiators. " 200 MW is a helluvalotta power! Disappointing to see it's so far off.

If we're talking of this kind of efforts, why not to discuss this - https://toughsf.blogspot.com/2019/10/the-expanses-epstein-dr... . Seems in the realm of physics, with some more impressing results...

One would have expected a narrative published in the last decade could have featured a more felicitously named phlebotinum.

Re: Magnetoplasma drive could make Mars transit take 39 days?

#44

Post by Ductapemaster »

sobellian wrote: post #30
sandworm101 wrote: post #15

https://www.spaceflightinsider.com/conferences/vasimr-plasma... http://spacenews.com/vasimr-hoax/ "Zubrin wrote in SpaceNews: “To achieve his much-repeated claim that VASIMR could enable a 39-day one-way transit to Mars, Chang Diaz posits a nuclear reactor system with a power of 200,000 kilowatts and a power-to-mass ratio of 1,000 watts per kilogram. In fact, the largest space nuclear reactor ever built, the Soviet[-…

The idea isn't ludicrous, although the torch-ship speeds of 39-day transits are definitely out of reach for now. The basic idea is, let's attach a nuclear reactor to an ion engine. Further, let's make the propellant hydrogen so we can refuel anywhere in the solar system. If we want to get serious about exploiting the solar system, we'll eventually have to give in and embrace nuclear technology, whether something like…

I love that we have ideas and theoretically a combination of technologies that can take us to Mars and beyond in a short timeframe. The way I see it is that while chemical rockets are un-economic, as you point out, for a large scale colony, what humanity needs is a demonstrated need and a catalyst to get us to explore the more exotic propulsion technologies like nuclear + ion drives + hydrogen.

Chemical rockets will take us from 0 to 1, and the economics will drive the next technological development to take us from 1 to n. I think it will work the same way as when telegraph wires were exploding around the US and we realized copper resources were a limiting factor. Did we give up and say "well, let's wait for the next technology"? No, we kept building the wires and other industries sprouted up to handle the demand (notably recycling).

Re: Magnetoplasma drive could make Mars transit take 39 days?

#45

Post by RandallBrown »

d_silin wrote: post #8

From what I heard from industry people, overheating is an unsolved problem for VASIMR. It is 60-70% efficient, meaning that 60kW of thermal power has to go somewhere. Waste heat management for 200MW system in space is firmly outside the realm of present-day technology.

Could you use the waste heat to boil something and then spray it out the back as extra reaction mass?

Re: Magnetoplasma drive could make Mars transit take 39 days?

#46

Post by [deleted] »

ColanR wrote: post #36
sandworm101 wrote: post #15

https://www.spaceflightinsider.com/conferences/vasimr-plasma... http://spacenews.com/vasimr-hoax/ "Zubrin wrote in SpaceNews: “To achieve his much-repeated claim that VASIMR could enable a 39-day one-way transit to Mars, Chang Diaz posits a nuclear reactor system with a power of 200,000 kilowatts and a power-to-mass ratio of 1,000 watts per kilogram. In fact, the largest space nuclear reactor ever built, the Soviet[-…

Your source is ignoring the fact that limitations on nuclear power in space are largely political. If we could put something bigger up there without concern it would be interpreted as a nuke, we would.

[deleted]

Re: Magnetoplasma drive could make Mars transit take 39 days?

#47

Post by extrapickles »

d_silin wrote: post #8

From what I heard from industry people, overheating is an unsolved problem for VASIMR. It is 60-70% efficient, meaning that 60kW of thermal power has to go somewhere. Waste heat management for 200MW system in space is firmly outside the realm of present-day technology.

I’m assuming you mean 60MW of heat, which would likely be worth recycling, especially if it’s not low grade heat. If you then are left with say 30MW of unrecoverable heat, than its only ~500x what the current largest space thermal system can handle (the one on the ISS).

It really depends on the mass budget they have for that speed for if anything new needs to be discovered.

Re: Magnetoplasma drive could make Mars transit take 39 days?

#48

Post by baybal2 »

sobellian wrote: post #30
sandworm101 wrote: post #15

https://www.spaceflightinsider.com/conferences/vasimr-plasma... http://spacenews.com/vasimr-hoax/ "Zubrin wrote in SpaceNews: “To achieve his much-repeated claim that VASIMR could enable a 39-day one-way transit to Mars, Chang Diaz posits a nuclear reactor system with a power of 200,000 kilowatts and a power-to-mass ratio of 1,000 watts per kilogram. In fact, the largest space nuclear reactor ever built, the Soviet[-…

The idea isn't ludicrous, although the torch-ship speeds of 39-day transits are definitely out of reach for now. The basic idea is, let's attach a nuclear reactor to an ion engine. Further, let's make the propellant hydrogen so we can refuel anywhere in the solar system. If we want to get serious about exploiting the solar system, we'll eventually have to give in and embrace nuclear technology, whether something like…

> The basic idea is, let's attach a nuclear reactor to an ion engine.

Why do you need to attach an ion thruster to a reactor, if you can turn the reactor itself into a thruster? https://forum.kerbalspaceprogram.com/index.php?/topic/151286...

Re: Magnetoplasma drive could make Mars transit take 39 days?

#49

Post by Pixelbrick »

sobellian wrote: post #30
sandworm101 wrote: post #15

https://www.spaceflightinsider.com/conferences/vasimr-plasma... http://spacenews.com/vasimr-hoax/ "Zubrin wrote in SpaceNews: “To achieve his much-repeated claim that VASIMR could enable a 39-day one-way transit to Mars, Chang Diaz posits a nuclear reactor system with a power of 200,000 kilowatts and a power-to-mass ratio of 1,000 watts per kilogram. In fact, the largest space nuclear reactor ever built, the Soviet[-…

The idea isn't ludicrous, although the torch-ship speeds of 39-day transits are definitely out of reach for now. The basic idea is, let's attach a nuclear reactor to an ion engine. Further, let's make the propellant hydrogen so we can refuel anywhere in the solar system. If we want to get serious about exploiting the solar system, we'll eventually have to give in and embrace nuclear technology, whether something like…

Totally agreed re: the necessity of doing what can be done [i]now[/i] within existing regulatory frameworks.

If & when we get round to allowing more exotic stuff to be used I like the look of this one.

https://www.nasa.gov/pdf/718391main_Werka_2011_PhI_FFRE.pdf

Re: Magnetoplasma drive could make Mars transit take 39 days?

#50

Post by Gravityloss »

ColanR wrote: post #36
sandworm101 wrote: post #15

https://www.spaceflightinsider.com/conferences/vasimr-plasma... http://spacenews.com/vasimr-hoax/ "Zubrin wrote in SpaceNews: “To achieve his much-repeated claim that VASIMR could enable a 39-day one-way transit to Mars, Chang Diaz posits a nuclear reactor system with a power of 200,000 kilowatts and a power-to-mass ratio of 1,000 watts per kilogram. In fact, the largest space nuclear reactor ever built, the Soviet[-…

Your source is ignoring the fact that limitations on nuclear power in space are largely political. If we could put something bigger up there without concern it would be interpreted as a nuke, we would.

Cooling is hard in space. It is hard and expensive to get good power to weight ratios.
Post reply on HN