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Magnetoplasma drive could make Mars transit take 39 days?

orbitalindex.com

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

#31

Post by onlyrealcuzzo »

sandworm101 wrote: post #24
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…

I think you should check your math again. 155,200mph = 69,380 m/s At 1g acceleration (10m/s/s) that is 6,938 seconds. 6,938 seconds is like 2 hours. A ship that can sustain 1g acceleration continuously for periods measured in hours, that would indeed be an interplanetary drive. Sustain that for days/weeks/months and it will take us to other stars.

How long do you need to accelerate at that pace to reach C? 299,792km/s / .01km/s => 29 million seconds? ~335 days?

I'm assuming a lot of things would go wrong as you get closer to C...

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

#32

Post by sandworm101 »

onlyrealcuzzo wrote: post #31
sandworm101 wrote: post #24

Earlier quoted context omitted.

I think you should check your math again. 155,200mph = 69,380 m/s At 1g acceleration (10m/s/s) that is 6,938 seconds. 6,938 seconds is like 2 hours. A ship that can sustain 1g acceleration continuously for periods measured in hours, that would indeed be an interplanetary drive. Sustain that for days/weeks/months and it will take us to other stars.

How long do you need to accelerate at that pace to reach C? 299,792km/s / .01km/s => 29 million seconds? ~335 days? I'm assuming a lot of things would go wrong as you get closer to C...

Or go right. Time dilation would start working in your favor. You might get there, and back, within your lifetime. Of course everyone on earth would be long dead.

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

#33

Post by Florin_Andrei »

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.

> It is 60-70% efficient

Funny - in a lot of other technology sectors, that would count as pretty good efficiency.

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

#34

Post by Florin_Andrei »

marta_morena_25 wrote: post #6
avmich wrote: post #5

Earlier quoted context omitted.

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...

Yeah this sounds cool. Essentially you could design a large spacecraft and put a fusion reactor in it (we will have viable, positive yield reactors soonish). It should be possible then to power a fusion drive as well by building a sort of "half-open" fusion reactor chamber into which we dispense some of the plasma without any pressurization. It should essentially cause a massive explosion, that if somehow controlled…

That's cartoon physics.

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

#35

Post by AnimalMuppet »

marta_morena_25 wrote: post #6
avmich wrote: post #5

Earlier quoted context omitted.

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...

Yeah this sounds cool. Essentially you could design a large spacecraft and put a fusion reactor in it (we will have viable, positive yield reactors soonish). It should be possible then to power a fusion drive as well by building a sort of "half-open" fusion reactor chamber into which we dispense some of the plasma without any pressurization. It should essentially cause a massive explosion, that if somehow controlled…

Even without relativity, the ejection velocity matters. To get the same change in momentum, you need to eject more mass if you have a lower ejection velocity. That means that you have to carry more mass to eject. And that means that, to accelerate that mass, you have to eject more mass. And so on. It just becomes really unworkable really quickly. (This is called the "rocket equation".)

As for the rest of your second paragraph: Look into how relativistic velocity addition works.

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

#36

Post by ColanR »

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.

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

#37

Post by dylan604 »

badwolf wrote: post #23
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…

Also importantly, you have to slow down at the other end.

If your ship can only handle 1G of acceleration, would that not also mean that it could only handle 1G deceleration as well? That means starting to slow down halfway to your destination.

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

#38

Post by snake_plissken »

sandworm101 wrote: post #24
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…

I think you should check your math again. 155,200mph = 69,380 m/s At 1g acceleration (10m/s/s) that is 6,938 seconds. 6,938 seconds is like 2 hours. A ship that can sustain 1g acceleration continuously for periods measured in hours, that would indeed be an interplanetary drive. Sustain that for days/weeks/months and it will take us to other stars.

Heh many thanks, you are correct. Somewhere in there I divided something incorrectly.

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

#39

Post by adwi »

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.

Any reasonable ways to recapture?

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

#40

Post by heimatau »

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…

This boils down to theoretical vs applied. The OP approx. stated that we're basically 1/100 of the way there and this theoretical drive is currently impossible to implement.

I've changed my career path because of these problems. I was a Math Major and now EE. These are the problems we need to be focusing on. Instead of using outdated and faulty technology from the 1960s.

IMHO, humanity is an inflationary species (for lack of a better term). We want to grow, spread and thrive. We aren't using a horse and a buggy. We (mostly) aren't shipping big chunks of ice around the world. We've made massive innovations happen and we should continue. It's nice that VASIMR is trying to push the envelop. Hopefully more of us can join together and tackle these big problems together.

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