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. …
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.
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) :)
As a Speccy nerd
Please, please, please tell me Ad Astra's company slogan is "To the stars!"
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!
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.
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.
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.
Pretty simple, really.
To slow down, you turn around and thrust in the opposite direction. If fuel burn is not a concern, 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.
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.
The calculations are for 50% acceleration, 50% deceleration. Leaving you with net 0 celeries. But at Mars!
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.
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.
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?
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.
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.
Don't be daft...
They accelerate for half the journey, coast for a day or a few hours and then decelerate for the rest.
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.
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.
My god that takes me back...
"Accelerate to ... Ludicrous Speed!"
How many of you actually remember this one?
Everyone's posted boring, sensible, low-risk answers to this question. I say keep accelerating til you get there, then lithobrake!
"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...
re: My god that takes me back...
Stopping is easy ...
Just aim for the centre of the planet....
It's not like Rocket Science is hard - it's not Brain Surgery you know...
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.
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?
Robert gets it
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.
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.
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.
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.
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.
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.
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!
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.
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.
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.
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.
"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).
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.
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.
"If you remove energy from a gravitationally bound system, IT HEATS UP"
it actually *speeds* up
Water down a plughole.
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?
270 HP - 148,500 foot-pounds per second? in space? Perhaps we'll start measuring the distance to Mars in peta-cubits.
What is that
In kilo swimmingpools?
Don't be silly.
If we are measuring power output in horse power, we should obviously then measure interstellar distances in furlongs.
I wonder if one day
VASIMR could be powered by Casimir
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.
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