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To Mars and Back in Ninety Days
paltemalte writes "A new means of propelling spacecraft being developed at the University of Washington could dramatically cut the time needed for astronauts to travel to and from Mars and could make humans a permanent fixture in space. In fact, with magnetized-beam plasma propulsion, or mag-beam, quick trips to distant parts of the solar system could become routine, said Robert Winglee, a UW Earth and space sciences professor who is leading the project."
This is fine and well, but how does one meanwhile solves the most pressing problem, that is, providing CHEAP and RELIABLE means to get into earth orbit???
Sign me up, should this ever become a reality. However, the only way space travel will become an everyday occrance is if it is profitable. Don't get me wrong. I'd love to do it for the sake of doing it. But people aren't willing to spend millions/billions/trillions of dollars to do something just because "its there".
/. is a bunch of nerds at a million typewriters. It's not a political conspiracy determined to undermine your beliefs.
What's all this about a "new method" being required for short trips to Mars? What about the 101 old methods we have? Nuclear Thermal, Nuclear Electric, Orion, Laser Lifters, Nuclear Salt Water (this seriously needs to be developed!), Fission Fragment engines, Nuclear Steam ships, etc, etc, etc.
We've got high powered propulsion options pouring out of our ears. It all comes down to getting funding. Wave a plan near congress and they're sure to kill it before breakfast.
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What are they looking at in creating particle or at least micrometeorite ablative shielding that can handle the increased velocity these hazards will bring with the increased speeds?
right now our spacecraft are basically beer cans with insualtion and windows, any tiny object at any decent velocity can rip through them like tissue paper. on a long distance mission as a trip to mars would be, we need a craft that is at least 100 times stronger than anything we launch now which would make it more than that many times heavier.
Do not look at laser with remaining good eye.
...this will only work for vehicles that have already arrived at their destination.
The article mentions having one station here and another on the other side, so that the craft itself need not carry its own propulsion.
However, any sort of malfunction - from the braking side not firing at the right time, to the braking side getting knocked off angle by a micrometeorite at the wrong moment, to the craft itself getting pushed off course - would mean that the craft itself would go hurtling through space with no real chance to be rescued.
The way around this? Keep an on-board propulsion system that's able to slow it down from full-speed back to 0, and then speed it up enough to get back to where you were going originally in a reasonable amount of time.
Which kind of defeats the purpose of the entire method.
That green slime had it coming.
Speed is relative. Meteors (including micrometeors) often travel 100's of thousands of miles an hour w/respect to the EARTH. A measly 20-40 thousand mph difference in ship speed isn't going to make much difference to one of these bad boys.
- The race is not [always] to the swift, nor the battle to the strong. -
..is there ANY realistic reason why sending people to Mars is good science?
No. There is no direct scientific reason to send humans to Mars. However there is a hell of a lot of capacity for new discoveries to be made and new technology to be invented by trying. Just look at the sort of stuff that came from the space program of the 50's and 60's. Likewise look at some of the stuff that came from [D]ARPA projects which on the surface had no direct scientific applications, but in retrospect gave us things like the Internet.
Setting lofty goals and spending money on pure research and development without having to worry about practical application or reason is a great way to produce really good, useful science. Not mention it makes you look really good if you happen to be the nation doing it.
You can always spin the spacecraft around. That's exactly what they do/did with the Space shuttle. You may be traveling at an obscenely high rate of speed, but you have 360/360 degrees of freedom for attitude. Haven't you ever played Asteroids?
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Can anyone tell me how the "pusher" satellite in the picture is supposed to work? I see one beam of energy with enough force to accelerate a spacecraft with a lot of force. Either there's an invisible other beam balancing this out, scorching the Earth underneath, or the satellite is doing a much better job of propelling itself out of the solar system than it is pushing the distant spacecraft where it's supposed to go. Or has someone figured out how to suspend Newton's second law?
It's all about weight.
The reason our spaceships are tin cans is because nobody can afford the weight for shielding. When 99+% of your mass is thrown away, carrying an extra kilo at the end means an extra hundred kilos at the start.
But, if you have a good enough fuel that you only need 10 times your ultimate mass in fuel, suddenly you can carry shielding. The better your specific impulse (I_sp = pounds of thrust per pound of fuel used per second), the better your chances for shielding. An I_sp of 200 (about what http://armadilloaerospace.com/ hoped to achieve) means you're just barely cutting it. An I_sp of around 300 makes life a lot easier, but that pretty much requires liquid hydrogen/liquid oxygen.
Anything higher than that is just pure nirvana for the rocket guys. I have heard of I_sp of over 1000 from a cesium ion drive, but that had just a teensy thrust, making it useful only for satellite station keeping.
So, in conclusion, if you can get a high I_sp and a high thrust, then shielding is a piece of cake.
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The cost and difficulty of shipping all of that material out to a Mars orbit, and maintaining it so it will be ready to deccelerate an incoming spacecraft would be Absolutely Enormous.
The article appears slashdotted. But,
Using this system means that you can't use conventional rockets and air-breaking to slow you vessel? Why can't the craft get a massive push from Earth orbit, then slow down using another form of propulsion once it gets to its destination?
Granted it makes coming home a major pain. Now you have to come home the old fashioned way. But, getting there isn't so bad... and sending supplies out to outposts doesn't take too much either.
The first few trips is to Mars in 45 days, to earth in 6 months. You can send all you want out to Mars or to meet a craft in transit in 45 days or less. Going home is a bigger problem.
Think... boot strapping... start small... build up infrastructure. Eventually when enough infrastructure is built up at a remote location you can do Plasma Jets both ways.
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For real perspective, running into all the space debris at this speed would be like hitting a brick wall in an F1 car.
We're going to need some kind of shielding.
Looks like 76 days each way, but with advances would only be a 3 month round trip
Yes. I've played Asteroids. I get pulverized in 30 seconds by a big rock because I'm going too fast. Is that what you meant?
Since the plasma is basically 'free' once the station is operational, merely direct an equal amount of plasma in the oppposite plane to the direction required for propulsion - the station would remain motionless, relatively. Mind you, I'd be carefull approaching the back door...
The last fucking thing you want is my undivided attention...
We've got a world full of nerds excited about spending months in a can to get to a world with no water and no air and no life that we know of, hoping to use the information gained on the trip to hop in another can to go to other worlds which will most likely have no air and no water.
Meanwhile, we're on a planet that our bodies have been custom built over billions of years to live on (with both air and water-perfection for us by definition) and we are so expectant at our own ability to screw the place up that we are trying to plan on the day when we'll have to leave this place because of what we've done to it.
Doesn't it seem a whole lot EASIER to just change our planet screwing habits than it does to attempt to terra-form a dry, red rock-which we would inevitably screw up in our same unlearned fashion?
This is a waste of money that would better be spent trying to figure out why we screw things up for the world around us so much better than we fix them. We have great success at helping our own species in specific fashions while screwing every other form of life up in general. Our myopic vision does not allow us to see big pictures, those that are more than 2 steps away from any cause or cure we undertake.
Any other planet with life on it out there would undoubtedly regard us as the trailer-trash that devalues the neighborhood. "Welcome!" signs are not in our future...
This reminds me of an idea from Larry Niven's Known Space stories. He thought that intrasystem transport would go through a phase in which photo-sail craft would receive an additional push from orbiting lasers sitting where they have access to high-density power supplies, making the light and simple vehicles fast enough to be practical for routine use.
:-)
:-/
(This plan figured interestingly in the first Man-Kzin War. Kzinti planners had not used reaction drives in so long that they failed to realize what a fleet of exawatt laser stations scattered all over a star system could do to an incoming force.
Come to think of it, long-range focused plasma beams could have military uses, even if they aren't dense enough to instantly zap the other guy out of existence. So, funding should be assured.
Because we all know that the steam engine, the universal governor, the printing press, the cotton gin, the combine, the internal combustion engine, the Model T, the airplane, the transistor, the integrated circuit, the telephone, the chemical battery, the capacitor, the steam tubine, the incadescent light, the phonograph, the film projector, the Compact Disk, and the mechanical loom are all examples of not much happening in the world because of the guiding principle of life being profit.
You can tell a great deal about the character of a man by observing those who hate him.
Imagine when 80 days around the world was an extraordinary and unbelievable accomplishment, now it seems that something as odd as 80 days around the solar system may be laughed at in a 100 years time.
In todays world, I cannot imagine how restrictive travel must have been, in tomorrows, they will pity us with our cars and segways!
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Depending upon the size of the pusher satellite, couldnt you just take an additional one with you. Once you arrive in orbit around mars, set up the return pusher for your trip home a few months later.
Once you do have the return pusher set up, that would mean you could basically start tossing out supply canisters to mars for free. No need to equip any preceding ships with conventional rocketry to slow it down, just give it big enough thrusters to maneuver and land.
You could modulize the entire operation. Use a "hopper" type craft to get the supply ships into orbit, then replace the hopper craft with the plasma sail module, and once you get to your destination use a landing hopper to descend. Seems you could be much more efficient if launch, transit, and decent all used specialized systems without the need to package all three together and pay for transporting the extera mass. Kinda liek how the spaceshuttle drops its booster rockets and fuel tanks after reaching orbit.
And there lies a lot of the problem with the space program. It's become cold and lifeless. You sound like a freaking accountant except that instead of counting dollars, you're counting quanta of scientific data.
We send people to Mars because it would be one glorious incredible acheivement of the human spirit and human will. We send people to Mars to hold our heads up high and say: Look what we can do, universe, now get out of our way.
And some day, the wild horses of humanity will go into space, and all the domesticated men and women they leave behind will huddle around their pathetic lives and fade away into the gray mist reserved for all mediocrity.
You can tell a great deal about the character of a man by observing those who hate him.
Don't count out the defense department either; I am betting the station in earth orbit they are talking about in the article used to kick a spacecraft out to the other planets could also put a nice big hole in selected ships/buildings/people here on earth. Just think of it as a dual-purpose satellite.
I Am My Own Worst Enemy
As I understand it, VASIMR and other plasma based systems require megawatts of power. I wonder where they are going to find a dense energy source that can provide that much power. Consider that the space shuttle only requires power on the magnitude of kilowatts. It would be interesting to see a nuclear powered (think submarine, not actomic bomb) spacecraft because that might be the best way we can put a dense enough energy supply on a craft.
Of course you need some kind of shielding, this is space after all. But your velocity has little to do with the danger of the debris that you will encounter. Speed is relative. Chances are that the debris that impacts your ship will be moving at 200,000mph. Even if you are motionless, you have the same type of impact. All space debris is not just sitting out there motionless waiting for some ship to fly into it.
True enough, but the likelyhood that you will encounter some form of debris increases with the distance that you travel. Sit in one spot, not a big deal. We know where a lot of that is and where it's going. Go rocketing around the solar system, Whoo-boy!
The Question 2 you raise is a good one. Presumably, since it's in earth orbit, we could keep shuttling fuel of some sort to it w/out too much effort (hah!).
I had considered that they might do that, but the end result is that you need *twice* the energy as a simple rocket. i.e. You've got the propulsive force from your plasma cannon and then you've got the force required to cancel out the former. Granted, it's not that hard to continuously boost LHOx tanks to LEO (~10-50 million per launch on a Delta II), but if you're going to do that you could have just strapped them to the Mars craft and ejected each tank as it ran out of fuel.
Honestly, the idea is not all that different from that of riding a laser "rail" via a solar sail. The engineering of a laser platform is certainly easier, and you could plant a bunch of them somewhere stable (like the moon or a Near Earth Asteroid).
The biggest problem I still have is that the launch window would be EXTREMELY tight for these devices. Launch *must* occur as Mars approaches Earth in its orbit, or you'd lose alignment as Mars passes around the other side of the Sun. The return trip would be pretty much the same issue. What that means is that either you get there and back in 90 days, or you'll spend the next 3 years on Mars.
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> With an energy model (e.g. you must climb to height X and introduce "potential energy" Y--escape velocity is derived from a kinetic/potential energy model anyway), it becomes unambiguous about how energy you've spent so gains you, and you can now integrate issues of energy lost to drag from doing anything other than flying straight up, and the validity of shooting straight up is clear.
In theory, you're correct, but there are other factors with the "space plane" design that change the balance. The first is that using a space plane means you only need to lift a portion of your craft out of the atmosphere, leaving the plane part behind, so you need less fuel on the "space" part of the plane. Second, the "plane" part of the space plane can incorporate an air-breathing engine, so you don't have to carry all of the oxidizer with you from the launch pad, like the shuttle does. This lowers the amount of total weight you need to lift, which (using proper mission design) could offset the extra energy you're using in a not-straight-up flight. Whether the savings from less oxidizer/less to-space weight can make up for the extra wasted energy remains to be seen, but I have high hopes that it can be.
Virg
I must have missed something in the article. I seem to remember Newtonian mechanics requiring that any force have an equal and opposite force. So, if this beam is going to push a craft, something must push the beam. And, if the satellite is pushing the beam, then something must be pushing the satellite. Now, if the satellite is sitting out in space, what's pushing on it? Isn't the satellite just going to fly backward (at a rate dependent on the ratio of its mass to that of the craft)? What did I miss in the article?