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Magnetoplasma drive could make Mars transit take 39 days?

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

#21

Post by SECProto »

a_crc wrote: post #11
api wrote: post #4

Earlier quoted context omitted.

How much thin film PV is that? There's no wind and the solar constant is a lot higher in space even further from the sun. Also remember that space is not dark. Unless you are behind something you are always in daylight if you are near a star.

It's a lot of solar panel. A quick search gives us a figure of 220 watts of power per square meter of space based solar panel. This would mean a 200MW solar collector would need to be almost a million square meters in size. For reference that would be a square the length of 155 NYC city blocks on each side.

> A quick search gives us a figure of 220 watts of power per square meter of space based solar panel. This would mean a 200MW solar collector would need to be almost a million square meters in size. For reference that would be a square the length of 155 NYC city blocks on each side.

200MW/(220w/m2) gives us an area of 1,000,000m^2, a square 1000m on each side.

(side note: a NYC block isn't a very good length reference - they vary[1] from 250ft to 750ft depending which direction you're measuring. So the square would be 4 to 12 blocks on each side)

[1] https://streeteasy.com/blog/how-many-nyc-blocks-are-in-one-m...

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

#22

Post by krastanov »

UnpossibleJim wrote: post #14
marta_morena_25 wrote: post #6

Earlier quoted context omitted.

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…

To my understanding of physics, there is almost no amount of thrust that would actually propel us to the speed of light, in reality. The energy costs alone would simply be too enormous. "Folding space"/"Warping space", or shrinking the space in front of the craft while expanding the space, would seem to be the only theoretical way to achieve speeds that not only would match light speed but could surpass it and not br…

Alcubierre is a Mexican physicist, not Spanish.

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

#23

Post by badwolf »

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.

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

#24

Post by sandworm101 »

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.

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

#25

Post by ashtonkem »

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.

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

#26

Post by jcims »

a_crc wrote: post #11
api wrote: post #4

Earlier quoted context omitted.

How much thin film PV is that? There's no wind and the solar constant is a lot higher in space even further from the sun. Also remember that space is not dark. Unless you are behind something you are always in daylight if you are near a star.

It's a lot of solar panel. A quick search gives us a figure of 220 watts of power per square meter of space based solar panel. This would mean a 200MW solar collector would need to be almost a million square meters in size. For reference that would be a square the length of 155 NYC city blocks on each side.

That's if it's illuminated by the sun. Blast it with a 500MW space-based laser and you'll up the tempo.

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

#27

Post by ashtonkem »

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.

I double checked, because I originally thought you were wrong, but it looks like you're essentially right.

32mi/s * (5280ft/mi) = 168,960 ft/s

168,960 ft/s ÷ 32.17405 ft/s^2 = 5,251.4371053691s

5,251s ÷ 60 s/min ÷ 60 min/h = 1.45hr

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

#28

Post by ben_w »

adrianN wrote: post #9
api wrote: post #4

Earlier quoted context omitted.

How much thin film PV is that? There's no wind and the solar constant is a lot higher in space even further from the sun. Also remember that space is not dark. Unless you are behind something you are always in daylight if you are near a star.

On Earth a commercial solar panel produces around 150W per square meter peak. I don't think you can improve this by more than an order of magnitude. Solar power drops off with the square of the distance to the sun. 200MW is a lot of solar panels.

Not by a factor of ten, but you can get 47.1% of the sunlight (which at 1 AU with no atmosphere is 1360 W/m^2), or 640 W/m^2.

Even then, 200 MW is a square 560 meters on each side.

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

#29

Post by thatcherc »

UnpossibleJim wrote: post #14
marta_morena_25 wrote: post #6

Earlier quoted context omitted.

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…

To my understanding of physics, there is almost no amount of thrust that would actually propel us to the speed of light, in reality. The energy costs alone would simply be too enormous. "Folding space"/"Warping space", or shrinking the space in front of the craft while expanding the space, would seem to be the only theoretical way to achieve speeds that not only would match light speed but could surpass it and not br…

It's actually that there is no amount of thrust that would propel you to the speed of light - no 'almost' about it.

From the perspective of an outside observer, a constantly-accelerating spaceship will approach the speed of light, but never quite get there. This will happen regardless of the level of thrust.

Alcubierre drives are pretty sweet - the only trick is they seem to require negative mass [0]... at least they've gotten down the requirement from a negative Jupiter mass to a mere -700 kg!

[0] - https://en.wikipedia.org/wiki/Alcubierre_drive#Mass%E2%80%93...

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

#30

Post by sobellian »

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 VASIMR or a nuclear-thermal design like NERVA. We already routinely park 100MW+ nuclear reactors in port for our navy, why not consider civilian use for space exploration? We already know many ways to mitigate risk for the launch of nuclear material.

I think Musk, Zubrin, et al. analyze propulsion technologies from the perspective of how to enable a journey to Mars now. In that light, something like Raptor makes much more sense. You still need a chemical rocket engine to lift off from Earth or Mars, so in the near term a nuclear ion thruster just adds far too much complexity to justify its inclusion. Further, it's difficult to imagine SpaceX obtaining the political backing to put nuclear tech into space as a private company. This is also why Musk would rather power Martian propellant plants with fields of solar arrays instead of the much more mass-efficient space-rated nuclear reactors that NASA has been developing.

But imagine if we actually developed a Mars colony with millions of people. The logistics of seeding a colony on Mars with chemical thrusters already boggle the mind. Economics would basically forbid meaningful interplanetary trade unless we develop new technology with much higher specific impulse. It would be even more impactful than moving from air-freight to container ships.

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