Astronomy Picture of the Day -- Curiosity Rover Lifts Off for Mars

NASA ^ | November 30, 2011 | (see photo credit)

[SunkenCiv]

Explanation: Next stop: Mars. This past weekend the Mars Science Laboratory carrying the Curiosity Rover blasted off for the red planet atop an Atlas V rocket from Cape Canaveral, Florida, USA, as pictured above. At five times the size of the Opportunity rover currently operating on Mars, Curiosity is like a strange little car with six small wheels, a head-like camera mast, a rock crusher, a long robotic arm, and a plutonium power source. Curiosity is scheduled to land on Mars next August and start a two year mission to explore Gale crater, to help determine whether Mars could ever have supported life, and to help determine how humans might one day visit Earth's planetary neighbor.

[SunkenCiv]

[Credit: NASA]

[SunkenCiv]

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[wastedyears]

Next August is too long. Don’t they slingshot anything that visits Mars around our moon?

[cripplecreek]

5 months isn’t too bad but if we really want to send people with any kind of regularity, we’ll need propulsion that gets them there in a few weeks.

[wastedyears]

It’s 9 months by my poor math.

[Moonman62]

Slingshot maneuvers save fuel, but they tend to take longer. This is one of the largest rockets we've ever used for a Mars mission, mainly because of the size and weight of the rover.

I believe somebody is working on a plasma engine that could get us to Mars much quicker.

[The Louiswu]

Saw it live and it was very cool
It is some thing everyone should try to see

[wastedyears]

How would a plasma engine work?

[momtothree]

Wow... you can almost “feel” the energy and power just in the picture. It must be awesome to see it live.

[traderrob6]

Drinkin again?

[Moonman62]

http://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_Rocket

[cripplecreek]

lol Yeah I suppose it is. pre coffee brainfart.

[TheOldLady]

So we still have a space program. Just unmanned. Like our pres_ent.

[GonzoGOP]

How would a plasma engine work?

Badly. The problem isn't with the plasma engines themselves, but with the power plants. In order to achieve the 39 days to Mars claimed by NASA, a VASIMR engine would need to be coupled to a nuclear reactor system with a power of 200,000 kilowatts and a power-to-mass ratio of 1,000 watts per kilogram. The best reactor achieved to date, the Soviet Topaz, had a power of 10 kilowatts and a power-to-mass ratio of 10 watts per kilogram.

To make matters worse the anti-nukers have put the screws to reactor research. So even if the power-to-mass ratios specified by NASA were possible, and a significant number of scientist and engineers doubt that, we won't be able to build and fly the experimental reactors necessary to find out.

Besides the VASIMR ship gets real big real fast. Can't launch it in one lift. So now you not only have to build a Battlestar, you need to build and orbiting shipyard too. This in an era where NASA can't get the budget to fly, well anyone.

The example I use is the 747 vs the Conestoga wagon. If you are going from St. Louis to California the 747 is faster, cheaper per passenger, safer, more reliable, moves more cargo and vastly more comfortable, even in coach. But the Conestoga departs in 1849, the 747 doesn't fly until 1969. And that 120 year head start is going to make all the difference.

You are better off going with smaller, lower tech, lower budget missions. Proper design can use the Earth departure stage as a counterweight to spin up the habitat module for gravity. And you can use to stores, water and fuel as a storm shelter against cosmic rays and solar flares. Yes you are going to Mars in a tuna can. And you spend more time in the can than the battlestar. But the tuna can is possible immediately within technical and budgetary restrictions. VASMIR might be used to colonize Mars some time in the late 21st or early 22nd century. But if you want to explore the place before then big dumb boosters and methane rockets are a much more workable solution.

[hattend]

They got that thing off the ground, with a plutonium power source, without some greenie group taking them to court?

Must be because of Obama.

[Las Vegas Dave]

Thanks for the ping. I watched it on DISH network/NASA TV.

It was GREAT!!

[Mmogamer]

What about an ion engine?

[GonzoGOP]

What about an ion engine?

They are well proven tech, and don't have the high power requirements of the plasma drives. Until someone builds an antimatter drive nobody will approach their ISP. On the down side the thrust to weight ratio is abysmal. So instead of simply blasting to escape velocity you spend weeks spiraling out.

The farther you go the better an ion drive works. At Mars they are only marginally better than a pure chemical rocket. The ion is always a hybrid because you still need a chemical first stage to get it into orbit, and a chemical engines on the lander. That is the rub. You have to drag along chemical engines and all the associated plumbing anyway. So you might as well just pack in a little more fuel and let them do Earth Departure. The small gain in trip time from a ion drive isn't worth the extra complexity and cost if you are only going to Mars.

The final consideration on a Mars mission is the idea of the free return orbit. Free return means that if the Mars orbital insertion / landing engine doesn't fire, you whip around Mars and come right back to Earth. Think Apollo 13, once on a free return orbit you are letting Isaac Newton do the driving. It isn't a fast trip, but it is a very safe trip. And the lander has enough food for a year on mars so if you don't land there are plenty of supplies for the trip back.

By its very nature an ion drive isn't on a free return orbit. Its whole efficiency comes from being under thrust the whole time. So if the engine fails you are outward bound forever. Not a big problem on a cargo or unmanned probe. You call Lloyd's of London and build another robot cargo ship. But if there is a man in the can it would be nice to have that automatic plan B.

To the asteroid belt they come into their own because of the ability to do lots of maneuvers at the destination. And and ion drive is more than enough to break away from the low gravity of an asteroid. Finally asteroids don't have enough gravity to do a free return orbit so that objection drops out.

Jupiter or farther and they are pretty much the only way to go. Chemical rockets just can't get humans there in a reasonable amount of time.

The best way of all would be a nuclear pulse drive. They have orders of magnitude more thrust than the biggest chemical rockets with the specific impulse close to an ion drive. Those things are 1950's tech so the problems are largely worked out. The 40 meter Orion would get 800 tons payload to Mars and back in only a couple on months round trip. Paradoxical the nuclear drive exposes the crew to less radiation. Since it has so much extra mass to play with you can put in much better cosmic ray shielding. And with a 40 meter diameter you can spin the thing up to Mars gravity at only 2.5 rpm. Well within human tolerance. But nobody is going to let you build one. And they play heck with launch facilities.