back to article NASA aims for space tests of Mars-in-a-month plasma drive

NASA will work with a firm started by a former astronaut to build a spaceworthy plasma drive capable of revolutionising travel beyond Earth orbit. However it appears that the space tests may not take place aboard the International Space Station (ISS) as had been planned. The VX-200 blasting Argon at full bore in ground trials …


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  1. LesC

    Space Sims -??

    Didn't the old MS Space Simulator have a Bussard ramjet or similar (low specific impulse but a *very* high top speed) with hydrogen tanks for the excess fuel? Been something like 10 years since I flew that all over the galaxy at .99c. Orbiter devs please note.

    Neat idea.


    1. Anonymous Coward
      Thumb Up


      I remember.

      Used to love the intergalactic freighter, the nimble craft that used to dart about the surface of the moon and Space Station Freedom (est: 1999) :)

  2. Greg J Preece

    As a Speccy nerd

    Please, please, please tell me Ad Astra's company slogan is "To the stars!"

    1. TeeCee Gold badge

      Re: As a Speccy nerd

      Well the company *name* is. You think they ought to say it in English as well so the thickies get the message?

      <Has a look>

      Holy crap! They have a "Mission statement" that tells you what they're actually planning to achieve, rather than some weaselly worded cobblers about customer satisfaction and / or the environment. This place really is run by people trying to actually do something!

      1. Greg J Preece

        Well yes, I know that

        I know what Ad Astra means. My comment was a game reference. On the Spectrum there was a game called Ad Astra, and the tagline scrawled across the cassette case was "To the stars!" It always used to amuse me. Great game, incidentally.

  3. Bill Neal


    39 days is great, but how do you slow down once you arrive? chemical rockets? Also, how many of these things could we strap together I wonder? The weight starts adding up fast.

    1. Anonymous John


      Accelerate for half the journey, turn the ship round, then decelerate for the second half.

      Not quite that simple of course as Mars is a moving target, but you get the idea.

      1. MacroRodent Silver badge


        For planets like Mars that have an atmosphere, you could also plunge partway into the atmosphere for braking. Requires a heat shield, of course, but would save lots of fuel.

    2. This post has been deleted by its author

      1. Michael Wojcik Silver badge

        Shortcut to Mars

        "your fastest route is to thrust forward for the first half of the mission, then at the halfway point (and your peak speed) you swing around and spend the rest of the journey slowing down again"

        Well, no - your *fastest* option is to accelerate toward it the whole way, and smash into the thing at top speed. But that's rough on the cargo.

    3. easyk

      sun's gravity well

      As I understand it... The Earth and Mars are orbitting in the Sun's gravity well. The energy from the engine accelerate the vehicle until it matches the orbital velocity (and thus orbital distance from the sun) of Mars.

    4. Martin Lyne


      The calculations are for 50% acceleration, 50% deceleration. Leaving you with net 0 celeries. But at Mars!

      1. seanj

        @Martin Lyne

        "The calculations are for 50% acceleration, 50% deceleration. Leaving you with net 0 celeries. But at Mars!"

        Net 0 celeries. Love it. Thank you for brightening up my Friday morning - but you still owe me for the keyboard...

    5. Tom Maddox Silver badge

      Presumably . . .

      You decelerate the way a regular rocket would: turn the ship around and thrust in the opposite direction. You just would have to do it for a longer period. Rocket scientists, being rocket scientists, will hopefully have thought of the whole "needing to stop" issue and planned appropriately.

      1. The First Dave


        It's not like Rocket Science is hard - it's not Brain Surgery you know...

    6. CaptainHook

      39 Days

      The plans I've seen quoted for Ion Drives Missions in the past has been based on half the time pointing at mars accelerating to ludicrous speed, turn around 180 degrees at the half way point and use the same engine to slow down.

      1. Steve the Cynic

        My god that takes me back...

        "Accelerate to ... Ludicrous Speed!"

        How many of you actually remember this one?

        1. Robin

          re: My god that takes me back...

          Me! Classic.

    7. Adrian Challinor

      The title is required, and must contain letters and/or digits.

      Oh you muppet.

      Weight in space is meaningless. I think you mean mass.

      Where's the icon for rocket scientist?

      1. Bill Neal

        Weight in space...

        Sending weight into space is not meaningless. every pound adds to the astronomical cost.

        AND YES I GET THE RETRO BURN CONCEPT. just that it doesn't seem to ever be mentioned anymore. Also if you chase down Mars in orbit, are you not exceeding orbital velocity?

    8. Aremmes

      Upon arrival

      To slow down, you turn the spacecraft 180° to point the engine in the direction of travel halfway through the trip and apply the same thrust. There's a video of this particular flight plan somewhere on the 'net.

    9. A Known Coward

      @ Bill

      You don't slow down when you arrive, you start slowing down at the halfway point using those same engines pointed in the other direction.

    10. Graham Dawson Silver badge

      Don't be daft...

      They accelerate for half the journey, coast for a day or a few hours and then decelerate for the rest.

    11. Robert Heffernan


      As the other replies to this post have said, the craft indeed does turn around at the half-way mark. But of interest is the 39 day trip time is inclusive of this maneuver.

      1. Bill Neal
        Thumb Up

        Thank you

        Robert gets it

    12. Rattus Rattus

      Slowing down

      Everyone's posted boring, sensible, low-risk answers to this question. I say keep accelerating til you get there, then lithobrake!

    13. Stumpy

      Stopping is easy ...

      Just aim for the centre of the planet....

    14. Cochituate

      39 Days to Mars

      the 39 day figure accounts for half the voyage speeding up, and once the craft flips over, the other half hitting the brakes.

  4. John Savard

    Specific Impulse

    This article does a very good job of making clear the distinction between systems like VASIMIR and conventional rockets. VASIMIR, like other advanced systems proposed in the past (i.e., ion drive) doesn't have the thrust to weight ratio needed to get off the ground, but the total amount of thrust it can produce before running out of fuel is much greater than for a conventional rocket, as is noted.

    However, the article did omit to note that the technical term for the latter useful end product of a propulsion system is referred to as "Specific Impulse", or I-sub-SP, which would have helped readers keep track of the more technical space literature.

  5. Anton Ivanov

    VF200 or VF2? Or VF200/1:100?

    VF2 will be an excellent match to the unmanned "black space helicopter", sorry spaceplane.

    Alternatively, who said that it will work continuously. Another advantage of VASIMR is that you can turn it on or off at will. Back of the fag pack calculation shows that 3-4 decent size batteries should be enough to run it at 1:100 duty cycle with several minutes continuous burn at time. More than enough for a test. Once again, the reduction in the amount of propellant the black space helicop^W plane needs to carry may probably justify that one as well.

  6. Johnny Canuck
    Thumb Up

    This is not a title

    Another benefit of the constant thrust/braking type mission would be the slight pseudo-gravity. This would have to be better for the astronauts health rather than the mostly weightless condition of the short powerful thrust/coast type.

    1. longbeast

      Only very marginal benefits.

      Even if you're making a spaceship that is stripped down to the theoretical minimum of an astronaut standing on top of a fuel tank and engine, no mass spared on comfort, you're still only going to be getting accelerations of about a thousandth of earth gravity.

      Acceleration-gravity of around 0.001G and lower isn't going to do much to help bone density loss and immune system function. It won't even really help with settling dust out of the air, since the air has to be circulated by fans anyway.

      It might make astronauts feel better in psychological terms to be able to feel a very faint downwards direction perhaps - giving some sense of direction.

    2. George Kapotto

      Shorter Trip

      39 days is a fairly short trip. even allowing for staging time at the ISS spaceport ;-) and prep time to land at Mars. The time in micro-gravity is on par with current ISS missions. Effects can be at least partially mitigated by currently known exercise regimes and equipment.

      There will be no need for huge Space Odyssey-type spinning ship to simulate gravity.

      btw - There is a Russian project going on right now where 'cosmonauts' are evaluating the psychological stress of a slow-boat mission to Mars. (365+ days in isolation if I remember correctly). They'll be pissed if no one ever actually spends that much time going to Mars.

  7. Ammaross Danan

    Nuclear Scaremongerers

    Nuclear scaremongerers are grasping at straws and spouting "what if it explodes on launch/re-entry???" They're akin to the religiously-biased backwards-thinking of the world, well, right up to current times almost. I would fully support proper nuclear power for space-faring craft, especially of a propulsion-testing nature. Of course, the space cannon of Final Fantasy (the movie) fame is what people are fearing. Have anti-satellite weapons (which we already have apparently...) and get on with it!

    1. Orv

      The risks are not so theoretical

      A Soviet nuclear-powered satellite re-entered after they lost control of it, and strewed radioactive material across a huge swath of northern Canada. Only a fraction was ever recovered.

    2. longbeast

      required title

      As the article mentioned, proper reactors have been flown in space already. They're not popular devices, as a few of them burst their coolant systems and spewed molten metal all over their orbit. Nuclear reactors have horrible potential for making the space debris problem worse.

      Shooting down satellites also has unfortunate space debris consequences.

      Nuclear power for an interplanetary mission is a great idea, and I wholeheartedly support it, but trying it in low Earth orbit when we haven't got any sort of debris cleanup strategy is asking for trouble. Keep it far away from orbits full of expensive satellite tech.

    3. Anonymous Coward

      Re: Nuclear Scaremongerers

      "Nuclear scaremongerers are grasping at straws and spouting "what if it explodes on launch/re-entry???""

      You either aren't very old or don't have a very long memory:

      Of course, radioisotope generators have been used extensively, and Lewis's "technofear protest" claims are just his usual hype. I imagine that most sensible people know the risks and rewards of such kit and accept its use even if they don't like nuclear power very much.

      "They're akin to the religiously-biased backwards-thinking of the world, well, right up to current times almost. I would fully support proper nuclear power for space-faring craft, especially of a propulsion-testing nature. Of course, the space cannon of Final Fantasy (the movie) fame is what people are fearing."

      I don't see how you can get off calling people names and then bring up Final Fantasy, Captain Sweatpants.

  8. JDX Gold badge

    nuclear space engines...

    seems in space is the ideal place for anything nuclear to me. Are the concerns based on sensible concerns like devices crashing during take-off and cracking open, or stupid worries about "making space radioactive"?

    Nice to see some people are still pursuing proper science.

  9. Joe User

    One question

    "VASIMR ships could get to Mars in just 39 days."

    Is that 39 days to go shooting past Mars, or 39 days to stop for a visit? In space, you accelerate to the halfway point, then turn around and decelerate for the other half (maybe a little less, if you can use gravity or an aerobrake at the destination to help you slow down).

  10. Anonymous Coward
    Anonymous Coward


    Interesting further development of a long toyed-with technology.

    Presumably the 39 days to get to Mars only refers to a "fly-by". To actually orbit the planet, you'd have to do a proportionate amount of deceleration to slow down enough, and then have the means to "inject" the spacecraft into orbit.

    Once there you still have the problem of getting a payload down to, and back off the planet. (Unless you're planning on the mooted one-way colonization mission).

    Aside from the huge amount of power needed, I missed seeing a reference in the article as to the actual amount of mass required to sustain such long trips.

  11. HurlingF

    Continually slowing it down...

    The additional drag removes orbital energy from the ISS complex. The altitude of the ISS is eroded and, thanks to the physics of orbital mechanics, it actually *speeds* up. A satellite in a lower orbit has a higher mean motion (a measure of orbital velocity) than one in a higher orbit. For example, the ISS orbits the Earth in about 100 minutes at around 350km, whilst a GPS Navstar takes about half a day at a tad over 20000km.

    1. Destroy All Monsters Silver badge


      "If you remove energy from a gravitationally bound system, IT HEATS UP"

    2. Anonymous Coward
      Anonymous Coward

      it actually *speeds* up

      Water down a plughole.

      1. Destroy All Monsters Silver badge

        Same difference


  12. John Smith 19 Gold badge

    There *might* be an intermediate option.

    Route *most* of the ISS power into a small high power phase array steered microwave array (site *well* away from the Earth) hitting a rectenna on a free flyer. IIRC that would be about 200 microwave ovens worth of hardware.

    Engine tested *without* needing an on board reactor (conventionally fueled compact 200Kw generators are on Earth as direct coupled gas turbines but I suspect the duration they could run before they ran out of fuel would not be enough for a really *through* life test) or a pricey c35m^2 triple junction cell array.

    Played properly it *might* (I've done no background research on this) be configured to carry a *small* (10s of Kg at best) payload to somewhere else in the solar system and *possibly* (depending on how good the trajectory design is) allow it to come back.

    It would be a bit like the solar sails JPL has been looking at for decades. The ISS is the "sun" and the system gains some flexibility as the flyers thrust vector can be altered (OTOH the "sun" might have to be switched off regularly as power is diverted to other needs).

    This has been one of those back burner projects at JPL since the 1970's. They say this thing could get to Mars in about a month. Why not *try* it?

  13. Steven Jones


    270 HP - 148,500 foot-pounds per second? in space? Perhaps we'll start measuring the distance to Mars in peta-cubits.

    1. hplasm

      What is that

      In kilo swimmingpools?

    2. Goat Jam

      Don't be silly.

      If we are measuring power output in horse power, we should obviously then measure interstellar distances in furlongs.

  14. AceRimmer1980

    I wonder if one day

    VASIMR could be powered by Casimir

  15. Remy Redert

    @P Henry

    Not sure on the specifics of the engine proposed for the mission, but 39 days from Earth departure to Mars orbital insertion with a good VASIMR engine and a nuclear reactor to power it is not at all an unreasonable figure.

    For example, a trip from Earth to Mars AND BACK! takes only 30 days if you can keep up a constant thrust of 0.01g (You will expend roughly 370,000m/s of DeltaV doing so). For a VASIMR drive with a specific impulse of 50km/s, that would require a ridiculously high mass fraction (Specifically, 1636:1. Meaning you carry 1636kg of propellant for every kg of spaceship)

    A slower transit, taking 39 days would result in considerably smaller mass fractions. A quick back of the envelope calculation gives a 7 to 1 mass ratio for a 39 day transit. Of course that doesn't get you into Earth orbit or down from Mars orbit.

    1. John Smith 19 Gold badge

      @Remy redert

      An MR of 7 (roughly 14% structure) is well within *stage* design capability (the Centaur stage is reckoned to be about the best at 8%) but the joker is the size of the power supply.

      Note that while it would *only* get you to Mars orbit in 39 days (compared to IIRC about 18 months for the usual proposed crewed trip) you can do quite a lot from orbit (including launch stuff that *can* land).

      The *real* payoff is that it would turn once-in-a-career design/launch/build opportunity for any given experiment into a 5 year experiment cycle (18 months-2 years to design/build your experiment package, results by radio/laser starting within 50 days then a year-18 months to analyse them and do the next version).

      That would be with *one* shuttle to Mars. From the engine makers PoV they get a mountain of telemetry to refine their design (and I'm sure that there will be *lots* of room for improvement once 1.0 is tested). Making it a bus service (once every few months) would give experimenters a solid timetable to work from. And of course once at Mars power would not a problem. A 200Kw generator (or receiver) could probably power most of the science experiments *ever* launched at the same time.

      Depending on how this test is handled the future could be very bright indeed.

  16. Anonymous Coward


    Is that a sporty Vauxhall?

    1. Anonymous Coward


      I've driven a VXR Vectra with more power than 270hp!

      Like the mars mission, it goes well in a straight line, but attempting to change trajectory it all falls apart and goes off on it's own tangent......

  17. Destroy All Monsters Silver badge

    Kill all Greens, get the Techno rolling!

    You know, when I was at uni and talked about nukes in space, other so-called "engineers" would decry the danger of "nuclear pollution of space". I had the terrible urge to bash in heads with a fire axe.

    "The fact is that even the launch of comparatively simple and low powered radioisotope-decay power units (as opposed to reactors proper) often draws a lot of technofear protest"

    Frack. That. Shit!!

    "and the bureaucracy and expense associated with spaceflight-rated nuclear technology is immense."

    Cut the red tape! Drop the regulatory horror! If need be, launch Doctor-No like from dead volcanoes in Zimbabwe or other cash-strapped places. They will be forgiving.

    1. Anonymous Coward
      Anonymous Coward

      "I had the terrible urge to bash in heads with a fire axe"

      I'm glad then that you are not in a position to make such decisions !

    2. Anonymous Coward
      Anonymous Coward


      It's not the releasing radiation is space that I have a problem with, it's the loading radioactive materials onto devices that are launched from the Earth. Remember GLORY crashed and burned last week?

      That's not to say that I'm anti-radioactive fuels in space, it's just that you really need to make sure that they're not going to be a hazard if they fall to Earth in a fireball. After all, you basically can't go away from the sun using power generated by PV cells, there just isn't enough light.

  18. Anonymous Coward

    I must be missing something

    Are they talking about using a solar array to power this thing to Mars? Because I'm thinking a big sail travelling at a very high speed isn't going to cope well with any debris it encounters along the way.

    1. longbeast

      Be optimistic!

      Sure it will!

      It's not going to be all on a single circuit in series. A solar array is, as the name suggests, an array - inherently built with some redundancy. You can prod holes in it all you like, and all you lose is a little bit of power where the actual damage happened. At worst you might have to shut down engines and EVA to reconnect a broken cable.

      There's not much risk of debris in interplanetary space though. Plenty of probes have gone that way before, solar panels unfurled all the way.

  19. BristolBachelor Gold badge

    200kW ??

    I'm currious as to where exactly the 200kW will come from on the ISS. To my understanding there is only 110kW user power available, and you would have to turn off everything to get all of that. I don't think that using all the solar array juice and not charging the batteries counts; the next 45 minutes without power would leave the ISS pretty dead. (Normally in sunlight half the array power charges the batteris for the next eclipse)

    Maybe the reason that this thing is car-sized if because it carries it's own juice as well as gas? The ones around here (although lower power) are more like the size of a remote controlled car rather than full-sized one.

  20. Ian 5

    Oh YES!

    it *is* rocket science... :o)

  21. Bobster

    "Variable Specific Impulse Magnetoplasma Rocket"

    Bloody hell! Sounds like something from Thunderbirds?!

  22. BossHog

    This pleases me...

    "The blue glowing engine exhausts in Star Wars are actually quite realistic, it turns out"


  23. Anonymous Coward
    Anonymous Coward

    Return journey time?

    If you need a seven to one fuel/structure mass ratio for a 39 day transit does that mean a 63:1 ratio for a return trip (assuming the Earth/Mars distance stays just as favourable for both trips)?

    Rocket science makes my head hurt.

  24. Remy Redert


    The 7 to 1 ratio is for a return trip, Earth orbit to Mars orbit and back.

    It's a bit high for commercial space flight still, but plenty low to use for Mars missions.

    And when the thing gets back to Earth, you can just refuel it and perform any required maintenance before sending it back out. It won't be a single use design.

  25. Stratman


    Does any uberboffin know why argon is the propellant of choice for the engine?

    1. Chemist

      Just a guess..

      'cos I'm an organic chemist but maybe it forms a plasma more readily. Its ionisation potential is quite low whilst having reasonable mass.

      On the other hand maybe it's the blue glow that makes your spaceship look like a 'proper' spaceship

  26. Jacob Lipman

    Nuclear reactors... in space!

    Nuclear reactors in space are the best answer. I approve the poster's plan to launch from a country that doesn't give a shit if nuclear material is sprayed all over the place in the event that the rocket stack goes kaboom.

  27. John Smith 19 Gold badge

    A note on Argon, nuclear reactors in space and alternative power sources.

    IIRC Xenon has been the preferred fuel for ion engines in space. It's *much* easier to store than Helium (the smallest atom) and being larger than Argon *should* be easier to ionize.

    However while Argon is likely to be harder to ionize (higher voltage power supply needed) it is also the most *common* noble gas in the atmosphere and perhaps most important of all, the *cheapest* as it's used in welding quite a lot.

    Being cheap and readily available (I'd expect large welding supply stores to have at least some in stock) can pay dividends when your research is on a budget.

    The problem with nuclear reactors in space (at least those in the *open* literature) is that they just are not *big* or current enough. The last *actual* US orbiting *reactor* was SNAP-10A in 1965, which was good for about 500W.

    The proposed SP100 (100Kw) for SDI in the early 80's never got out of design. Los Alamos has been designing something called the SAFE400, designed to deliver 100Kw of electrical power, as a sort of private project of the director, and that's about it in the US (of course the NRO, USAF and USN *could* have one on every big sat they've been orbiting since the 80s and simply not *told* anyone. However the presence of high temperature neutron emitting IR sources *anywhere* in Earth orbit would be a pretty big hint *someone* was using them and the list of countries that could is a short one).

    The US bought 6 TOPAZ reactors in the early 90s (and AFAIK still has them) but I don't think they bought any *fuel*. However even if they were good to go they would deliver about 5Kw


    Bottom line. No one is going to design, build and qualify a space nuclear reactor in the timescale needed (although a space reactor design in the 100Kw+ range, which gave more power than all but the *biggest* solar arrays, *would* be a good idea to have on the shelf for the future)

    Ground based turbo generators in the 200Kw range are used for emergency power and typically fueled by gasoline or natural gas. Assuming sea level air has a density 1.22521 kg/m3. and 20% of that mass is O2 then LOX is 4562x more dense (per cubic metre). It *should* be possible to build a power pack (LOX/fuel tanks, turbo-generator, controls) into a package you could stow on the Shuttle.

    While it would be enough to *start* the engine it's *very* doubtful to get the kind of run time that would be needed to show up any flaws that *only* shoe up in long term tests (936 Hrs, possibly with a re-start following flip over at the half way mark if you really want to go to Mars)

    BTW the way to avoid the exhaust interfering with the thrust measurements is to fit the exhaust pipe with a T end piece that exhausts in equal and opposite directions, canceling any thrust.

    Wiring this thing *directly* to the ISS power system and directly mounting it to the structure is *much* the simplest option.

  28. Neil Stansbury
    Thumb Up

    Electromagnetic Shielding?

    The extra exciting part, is the very large magnetic fields generated by the engines' super conducting magnets.

    I wonder if these could be used to provide an artificial magnetosphere for shielding the crew on long duration manned voyages.

    The engines also generate a magnetic torque that perhaps could be used to rotate the crew capsule creating a centripetal force to create artificil garvity.

    Solutions to two long-duration flight travel problems as a result of a by-product!

  29. Bronek Kozicki

    mass in space

    ... multiplied by speed turns to inertia, which must be preserved (unless opposite ... etc).

    So it does matter, only differently.

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