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Magnetoplasma drive could make Mars transit take 39 days?
- blakesterz 6y ago"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.
- tectonic 6y agoBut usage on smaller, uncrewed probes could be much closer.
- api 6y agoHow 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.
- Majromax 6y agoThe linked article also makes a comparison with the ISS solar arrays, which provide 120kW of power. They're not the most efficient panels out there, but it's hard to make up three orders of magnitude.
- adrianN 6y agoOn 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.
- ben_w 6y agoNot 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.
- a_crc 6y agoIt'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.
- api 6y agoHmm... or maybe some smaller panels plus a really enormous and very very thin reflective collector for concentrating solar. Keep in mind that things can be very thin in space. It would still weigh a lot though, and heat would be a major issue. You wouldn't want to melt the solar panels. This would require someone much more knowledgable to determine if it's feasible. Edit: I wonder if you'd get some amount of solar sail effect in addition to the plasma rocket? Of course this would help you one way and hurt you the other way.
- codeduck 6y agoA million square metres is one square kilometre. It could be built but it would be heavy. A circular sail with a radius of just over 600 metres would do it.
- SECProto 6y ago> 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-mile/ https://streeteasy.com/blog/how-many-nyc-blocks-are-in-one-m...
- avmich 6y agoIf we're talking of this kind of efforts, why not to discuss this - https://toughsf.blogspot.com/2019/10/the-expanses-epstein-drive.html https://toughsf.blogspot.com/2019/10/the-expanses-epstein-dr... . Seems in the realm of physics, with some more impressing results...
- marta_morena_25 6y agoYeah 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 by magnetic fields, should yield an enormous forward thrust. Technically, does it even matter how fast we eject? Shouldn't relativity allow us to reach speed of light with any positive thrust velocity? If the speed of the shuttle was of any concern, that should directly invalidate relativity, since passengers would suddenly not perceive any acceleration anymore, even though nothing about the spaceship and its physical reaction has changed.
- UnpossibleJim 6y agoTo 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 break the laws of physics as we understand them. The drive Alcubierre proposed in the 80's, I think... maybe the 90's. I'm not sure when. A Spanish mathematician or physicist who was a fan of Star Trek. EDIT: My understanding of physics is pretty minimal. I'm more than happy for someone to correct me and explain what I got wrong. This type of stuff is fascinating.
- krastanov 6y agoAlcubierre is a Mexican physicist, not Spanish.
- d_silin 6y agoFrom 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.
- Florin_Andrei 6y ago> It is 60-70% efficient Funny - in a lot of other technology sectors, that would count as pretty good efficiency.
- rbanffy 6y agoTrue, but radiating 30-40% of your waste heat isn't that easy.
- adwi 6y agoAny reasonable ways to recapture?
- RandallBrown 6y agoCould you use the waste heat to boil something and then spray it out the back as extra reaction mass?
- ryanmarsh 6y agoYes, but what? You have to lift that mass to orbit. What mass boils off with greater energy than, say, mass that combusts?
- TheOtherHobbes 6y agoYou don't necessarily need to lift that mass to orbit for interstellar flight. https://en.wikipedia.org/wiki/Bussard_ramjet https://en.wikipedia.org/wiki/Bussard_ramjet
- Symmetry 6y ago
- natcombs 6y agoUsing nuclear bombs for propulsion was estimated to make it to Mars and back in 4 weeks. First time I heard of this, I thought it was a joke. https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion The project Orion study anticipated a one-way trip could reach Alpha Centauri in as short as 133 years
- jandrese 6y agoI would take the figures from Project Orion with a grain of salt. It was very much a cocktail napkin exercise.
- elihu 6y ago> The most recent tests of VASIMR have run at 200 kW and expelled ions at 180,000 km/h Is this the power consumed by the device, or a measurement of the propulsion power created? It would be interesting to know the energy efficiency; i.e. what percentage of the input power is converted to thrust.
- d_silin 6y agoAt least 60%.
- sandworm101 6y agohttps://www.spaceflightinsider.com/conferences/vasimr-plasma-engine-earth-mars-39-days/ https://www.spaceflightinsider.com/conferences/vasimr-plasma... http://spacenews.com/vasimr-hoax/ 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[-era] Topaz, had a power of 10 kilowatts and a power-to-mass ratio of 10 watts per kilogram. There is thus no basis whatsoever for believing in the feasibility of Chang Diaz’s fantasy power system.” Note the word used by spacenews: Hoax.
- sobellian 6y agoThe 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.
- Animats 6y agoYou still need to carry reaction mass. It just gets pushed out the back faster. It's another variation on the nuclear rocket idea.
- pinewurst 6y agoSeriously, I've been reading VASIMR press releases for the last 20 years or so. Looking into it, I get the impression it's more a livelihood (from grants) for the inventor than an ongoing technological trajectory.
- snake_plissken 6y agoSome quick math: 32 miles per second (see one of their linked articles, https://www.spaceflightinsider.com/conferences/vasimr-plasma-engine-earth-mars-39-days/ 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 useful to transport space crews? Still really cool tho.
- ashtonkem 6y agoAnd 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.
- skunkworker 6y agoIf 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.
- badwolf 6y agoAlso importantly, you have to slow down at the other end.
- dylan604 6y agoIf 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.
- jandrese 6y agoI think it would be more like you time your arrival with the conjunction of some gas giants in the destination solar system and aerobrake multiple times to get your speed low enough so you can aerobrake on your destination planet. Bringing enough fuel to decelerate the same way you accelerated isn't usually practical, inflating your rocket by 15x its original size or more.
- tectonic 6y agoIf you're into this sort of thing, we write about nerdery like this every week in The Orbital Index :)
- catmistake 6y agoEveryone is missing the fact that even if this technology was available 100 years ago, and worked just like we wanted, you could not get to Mars in 39 days. It would take about twice as long, because you have to turn the ship completely around half way to the destination and slow down pretty much for the same about of time it took to get to whatever velocity. And Mars is a rock. I am sure there are astounding discoveries to be made, but resources would be far better spent fixing ourselves and what we've done to the planet before we cause our own extinction. Maybe we can do both, but let's not ignore the fact that we have major problems, and it is unlikely we'll ever find a better home than Earth.
- peter_d_sherman 6y ago>"VASIMR (Variable Specific Impulse Magnetoplasma Rocket) is a helicon magnetoplasma thruster designed to provide a variable thrust profile, from low-specific-impulse / high-thrust to stupidly-high-specific-impulse / low-thrust. Specific impulse could max out at ~12,000 seconds, drastically higher than the roughly 2,000 s from current hall thrusters. VASIMR creates thrust through a multi-step process. First, it bombards a neutral gas with RF energy in helical waves to ionize the gas and create plasma (it can use multiple gases: argon, hydrogen, or even CO2). Then, it uses magnetic fields and an additional RF coupler to contain and energize the plasma to a superheated state (in the neighborhood of the temperature of the Sun’s core). Finally, a magnetic nozzle ejects the plasma at exceptionally high velocity. The most recent tests of VASIMR have run at 200 kW and expelled ions at 180,000 km/h (test fire video… or a blue party light being turned on, we’re not sure). 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..." Thoughts: We need a functioning ITER -- in space...