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back to article Solar-powered ion drive asteroid probe set for launch

NASA has confirmed that the "Dawn" space probe to the asteroid belt will indeed launch on Saturday, ending speculation that the mission might be delayed. After launching, Dawn will spend four years in transit to the asteroids, circling the Sun twice and gaining a "gravity assist" on the way by making a close approach to Mars. …

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Silver badge

Not a very SMART article ;-)

ESA was there first with the SMART probe to the moon!

Once in space the best form of acceleration is gravity which is why it's used by all projects: free and very powerful

Interestingly ion drives are one of the areas of patent contention between NASA and ESA with presumably the US department of defence not keen on any "competitor" having access to the same technology. I thought the US version used a nuclear reactor rather than solar panels to energise the propellent.

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Bronze badge

patent contention?

I refer the court to the case of noodles vs spaghetti.

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A couple of corrections to the previous post.

An experimental ion engine was flown on the Zond 3 probe in 1965, so SMART itself was beaten to the punch by some decades.

Also, nuclear-ion drives have been designed on paper, but not yet been launched. Dawn does indeed rely on solar panels for its electricity, as stated in the article.

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TWIN Ion Engine?

Anyone?

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Is this a way of recycling old irons?

We have a couple in the cupboard we could send to NASA if it would help.

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Bronze badge

CO2

So, I'm supposed to turn off my lights to save the world, while NASA produces as much CO2 as a small country in one lanch!

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Ion Drive

Dawn uses Chemical rockets to reach escape velocity, so SMART-1, which reached escape velocity entirely by ION propulsion still has the edge!

Also, what's all this "0.02lb" nonsense? At the very least you should consider the other 95% of the planet that doesn't use Imperial* measurements. Hang on, I'll save you the trouble.. 0.02lb, that's er 2.2lb => 1Kg, or 9.81N at sea level. So, 0.02lb is: 0.1N, impressive, Smart-1 only managed 68mN.

-cheers from jules @P.

(*or 'English' measurements as US refers to it, even though 'English' measurements are largely Metric these days).

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RE : patent contention?

in the voice of comic book guy from the simpsons :

"Best Comment Ever"

nice one

dude

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hmm, I remember this one well

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

good thing there's no people there... I think the spaceship in that book was ion powered :S

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Anonymous Coward

Lift off

"Dawn uses Chemical rockets to reach escape velocity, so SMART-1, which reached escape velocity entirely by ION propulsion still has the edge!"

SMART-1 was launched by an Ariane rocket. This may have helped it on its way?

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Re: CO2

That the main exhaust of the shuttle is produced from burning hydrogen and oxygen. The SRBs use ammonium perchlorate and aluminium (not hydrocarbons), and the mass of propellant in an SRB (the only engine that even has hydrocarbons on the shuttle system, for example) is 499,000 kg. Of that mass most is ammonium perchlorate (no carbon). Only 12% is the hydrocarbon binder. The US on average burns 1.51 billion litres of gasoline every day. Do the maths yourself; one shuttle launch is barely a drop in the bucket.

Incidentally, "Dawn takes ages to squirt out a given amount of fuel" - this sounds like he's been watching the same internet porn as I do.

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Pounds and ounces

0.02 lb-force =approx 0.3 ounce-force = 92 millinewtons ie 0.092 not 0.1.

It's the same engine as DS1 - three on-board but only one in use at a time. http://en.wikipedia.org/wiki/Deep_Space_1

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Anonymous Coward

Nasa should really consider

using electrodynamic ion drives instead of electrostatic ones. They are more powerful, can work with hot plasma (usable for fusion systems), and because the magnetic fields the plasma never touches the drive so there is no accelerator grid to get stuffed. The problem with them is that they need more energy unless one uses superconductors. (which is imho quite doable in deep space) For a fusion powered system, which already has high magnetic fields and produces ionised helium as an exhaust an electrodynamic ion drive will be the best solution. (today, we could use plutonium based batteries for the same purpose)

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Silver badge

Vesta arrival/Vesta departure

Are we sure the graph shown in the article is not a Microsoft OS rollout plan? They must have misspelt the name though - Vista, not Vesta, right?

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Anonymous Coward

CO2

"So, I'm supposed to turn off my lights to save the world, while NASA produces as much CO2 as a small country in one lanch!"

Yes but it's for science, so that's okay. Anything done in the name of science is fine, and anyone who objects is a luddite religious fundamentalist.

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Re:Nasa should really consider

I'm sure the thousands of scientists and engineers employed by NASA and its subcontractors are giving themselves a collective slap-on-the-head for not thinking of that solution first.

Maybe they've got better reasons than 'imho', Mr/Mrs Armchair Anonymous Critic.

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This Article is Better Than the One In Aviation Week

In that article, the writer drew analogies between ion and Star Trek, because both drives glow blue.

see http://fourtyyears.blogspot.com/2007/07/note-to-aerospace-journalists-star-trek.html

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Getting picky!

With regard to:

"Lift-off" SMART-1 of course got into orbit via a chemical rocket, but it's still the only spacecraft (AFAIK) to travel from there to another body using an Ion drive.

"Pounds and Ounces": Hmm, "approx 0.3 ounces" translates into mN accurate to 4 decimal places? If we want to be more accurate, 0.02lb should be more like 89mN, not 92mN.

-cheers!

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Re: This Article is Better Than the One In Aviation Week

Writing aimed at the lowest common denominator, no doubt.

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re: Nasa should really consider

Nasa should really consider launching ITER into space? I dunno, it looks pretty heavy to me. Besides, I think the French, amongst other participants, would object.

From what I've heard, while producing fusion reactions is easy to accomplish (though technically complicated), no one has been able to produce a fusion power generation system that produces more energy than consumed by its power-producing mechanisms.

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