Ion engine could one day power 39-day trips to Mars

[DainBramaged]

There's a growing chorus of calls to send astronauts to Mars rather than the moon, but critics point out that such trips would be long and gruelling, taking about six months to reach the Red Planet. But now, researchers are testing a powerful new ion engine that could one day shorten the journey to just 39 days.

Traditional rockets burn chemical fuel to produce thrust. Most of that fuel is used up in the initial push off the Earth's surface, so the rockets tend to coast most of the time they're in space.

Ion engines, on the other hand, accelerate electrically charged atoms, or ions, through an electric field, thereby pushing the spacecraft in the opposite direction. They provide much less thrust at a given moment than do chemical rockets, which means they can't break free of the Earth's gravity on their own.

But once in space, they can give a continuous push for years, like a steady breeze at the back of a sailboat, accelerating gradually until they're moving faster than chemical rockets.

Several space missions have already used ion engines, including NASA's Dawn spacecraft, which is en route to the asteroids Vesta and Ceres, and Japan's spacecraft Hayabusa, which rendezvoused with the asteroid Itokawa in 2005.

But a new engine, called VASIMR (Variable Specific Impulse Magnetoplasma Rocket), will have much more "oomph" than previous ones. That's because it uses a radio frequency generator, similar to transmitters used to broadcast radio shows, to heat the charged particles, or plasma.

http://www.newscientist.com/article/dn17476-ion-engine-could-one-day-power-39day-trips-to-mars.html?full=true

http://brightcove.newscientist.com/services/player/bcpid1873822884?bctid=29691708001 <------------------VIDEO, so cool



Water on the moon, hah!

[donco6]

1. If it accelerates slowly, how does it slow down quickly?

Do they have to preserve fuel for deceleration? (sp)

[DainBramaged]

2. I do not know, I only post da article

but I am SURE they'll have it figured out by the time they are ready to fly to mars! Maybe solar sails like in Star Wars? Wow and the turds are un-recing the thread already. :puke:

[Sinti]

41. Look at the Japanese space-based solar array project

http://www.engadget.com/2008/02/07/japans-space-agency-planning-space-based-solar-power-arrays/

There could be technology to use the sun as power also - very much like solar sails. Sometimes I think art (science fiction in this case) informs science as much as science informs art.

[Statistical]

4. It doesn't. It decelerates just as slowly.

Simple version

Conventional rocket:
Fire rocket for few seconds to few minutes.
Coast for couple days (99% of time)
Fire rocket for few second to few minutes to slow down (Mars gravity is used to pull ship into orbit = same speed but now circling the planet).

Ion rocket
Fire rocket constantly for 20 days to accelerate.
Flip craft over so engine faces mars
Fire rocket constantly for 20 days to decelerate.

Ion engine is much slower on shorter trips like to the moon. 14 days vs 3 days however they are far more efficient so they can carry more cargo and less fuel for a given size. Important is you want to reduce cost of supply runs to the moon.

For longer trips (like 6 months to mars) the constant acceleration means it can shorten the trip but it is also useful for short trips (albeit longer travel time).

[donco6]

13. Thanks - really interesting.

So it sounds like they'll have to "launch" this from orbit? Bring the astronauts to ISS and load the craft from there?

[StarfarerBill]

5. Perhaps with aerobraking:

dipping into Mars's upper atmosphere to provide friction and thus deceleration...assuming, of course, that its thin atmosphere would suffice without the spacecraft descending too deeply into the planet's gravity well.

[Statistical]

7. Aerobraking is possible but too dangerous for humans.

If you have a malfunction and fail the areobraking the crew would travel past mars and out of solar system with no method to turn around or be saved. Eventually they would die from lack of oxygen and water.

Not something NASA will consider at this point.

Instead you accelerate towards mars. At half way point you flip ship end over end so rocket is facing mars and decelerate for second half of trip.

[StarfarerBill]

16. Who knows?

With some of the advanced propulsion systems being considered, perhaps NASA is also mulling over more radical ways of slowing them down.

And thanks: I do understand basic zero-G/vacuum physics. I guess I just couldn't see how any spacecraft could make it to Mars in only 39 days with half of that time spent decelerating; so I thought aerobraking would be a solution to that.

[Statistical]

19. The magic of constant regular acceleration

d=0.5*a*t^2
thus

a = 2d/t^2

19.5 days = 1,684,800 seconds

60 million km to mars so half way point is 30 million km. ship must travel 30 million km in 19.5 days at constant acceleration

a = 2 * 30 billion m / 1684800^2 = 0.2114 m/s^2

With acceleration of only 0.2114 m/s^2 the ship will reach half way point in 19.5 days and have a peak speed of 35 km/s = 126,000 km/h.

The 90% reduction in fuel also enables the ship to be much lighter or carry larger cargo.

Plus the system could be made more efficient by using booster. On launch from earth orbit a conventional booster could provide initial acceleration and then be discarded.

[StarfarerBill]

29. Gotcha.

I didn't realize a relatively low-powered system like an ion engine could accelerate/decelerate that speedily.

Thanks for the clarification, Statistical. :)

[SidDithers]

36. Wouldn't want to have something go wrong during deceleration...

that would be a bad thing

Sid

[spin]

64. Somewhat like untaxed compound interest...

at first the money you have invested doesn't seem to be increasing very fast, but come back in 40 years.

[Statistical]

65. Very good analogy.

Work exactly the same.

The Chemical rocket provides a substantial and constant velocity(once it finishes accelerating after few minutes).

For first 1/4 of the trip the spaceship would actually be traveling slower than a conventional chemical rocket. However around the 25% point it passes the chemical rocket and continues to accelerate until the halfway point.

It is like the classic question
Which would you rather have $1000 a day for a month or a penny on first day and double it each day ($0.01, $0.02)?

[drm604]

18. If you have a malfunction during deceleration you end up with the same problem.

Either method could fail, both with fatal results. Having to start deceleration halfway through the trip increases the trip length thereby increasing all of the dangers that go with a longer trip.

It's a question of overall safety. Is aerobraking inherently less reliable than decelerating for half of the trip? I don't know the answer to that, but it seems like an important question.

[Statistical]

21. You have chance to fix failure in 19.5 day deceleation.

1) Engine could be repaired.
2) Likely there are multiple redundant engines
3) Engines are likely run at less than full capacity so their output can be increased to compensate for output lost from damaged/offlne engines.
4) Deceleration will take 19.5 days giving time to overcome errors.

My asumption would be that NASA would build something will multiple engines and some hot spares all operating at something like 80% of max. Say 10 engines with 8 firing at 80% would provide lots of contingencies for any emergency.

Aerobreaking will take a matter of minutes, expose the ship to massive G force (slowing from 35km/sec), and any failure will be instantly fatal.

If the ship undercuts the the aerobreak it burns up, is it overcuts the aerobreak it glances the atmosphere and goes into deep space. The margin of error is small and there is insufficient time

The major advantage of ion engine is it can accelerate/decelerate the entire trip making the need for aerobreaking redundant.

[drm604]

25. Good points. n/t

[Confusious]

43. I don't think mars has enough of an atmosphere to aerobrake......eom

[backscatter712]

62. Aerobraking can work, but everything has to go exactly right.

Go too shallow, and you don't slow your ship enough and you skate off past Mars into deep space - sucks to be you.

Go too deep and you die in a spectacular fireball.

Though if the ship had human pilots aboard, they might be able to react better than computers in an emergency situation and make sure the aerobraking goes right.

[Pab Sungenis]

14. That would be the best bet.

Chemical rockets to decelerate quickly.

[Statistical]

15. That would be hugely expensive in terms of weight.

You would need to carry all that conventional fuel the entire trip.

Considering fuel weighs nearly twice that of entire rest of mission would have increased the weight cost by 50%.

Now you need 50% more ion engines to accelerate the craft.

No the goal is to eliminate all conventional rockets except for small ones used in positioning.

[Pab Sungenis]

32. You'd need conventional fuel for a landing, anyhow.

Unless, of course, you never planned on taking off again. Even if you go to the "landing module/command module" model of Apollo, you'd still need conventional fuel for the lander to take off.

My bet would be a combination of ion "retro rockets" fired in advance of orbit insertion to slow back down gradually, with some combination of "braking" conventional fuel rockets to finish deceleration and maneuver into orbital insertion. Then after the return of the landing party, a short burn of conventional to break orbit and maneuver onto course for a new ion burn for the return trip.

To reduce launching costs, I would assume a Mars mission ship would originate from the ISS, not from the ground. It could be assembled and fueled in Earth orbit and dock at the ISS on return.

[csziggy]

55. One proposal I saw years ago suggested sending an unmanned "factory" ahead

To produce fuel for the take off and return trip. I am not technological knowledgeable enough to understand or remember the details, but they were making assumptions about the composition of the soil based on early Mars missions and what elements and compounds they could harvest and produce.

The basic idea was that before the manned mission ever took off there would be enough fuel stockpiled on Mars for a return trip. How much easier if there only had to be enough to power a chemical rocket to get the return vessel into orbit and let the ion rocket power the interplanetary trip!

ETA: Here it is: Mars Direct. My memory of the details is not quite right: http://www.nss.org/settlement/mars/zubrin-promise.html

[Statistical]

66. Yup good way to merge both technoligies.

Carrying fuel is insanely inefficient.

Anything you can do to avoid it frees up tons of fuel.

Having the fuel to launch the lander on Mars and ion drive for both legs of trip means the conventional fuel requirements can be reduced to steering rockets (rocket to insert craft into Martian orbit) and rockets to slow descent to Mars.

You go from carrying literally 60-80 tons of conventional fuel to carrying maybe couple hundred kg of fuel. The mission is lighter, cheaper, and capable of carrying more useful cargo.

[csziggy]

54. The size engine for going to Mars would be powered by a nuclear reactor

So fuel is not a big problem compared to chemically powered rockets. The spacecraft could accelerate until halfway there, turn around and decelerate the rest of the way, rather than accelerate to the desired speed in a short time, coast most of the way, then a short deceleration at the end as current technology would require.

This would make a huge difference in space flight!

[snake in the grass]

3. Who the fuck would unrec this?

Really, who are you and what's your problem? Did Mama do too much meth during the pregnancy?

[Statistical]

6. Anti-science nuts.

The ones who think money is "spent in space" and thus wasted.

However they forget all the money is actually spent on earth providing jobs, living wages, and scientific research.

[SidDithers]

10. The ones concerned that astronauts will be raping the Red Planet...nt

Sid

[Odin2005]

23. The resident luddites.

[name not needed]

28. The same idiots who cried about the "moon bombing"

[Regret My New Name]

31. WHAT??? THE MOON WAS BOMBED?? WE BOMBED THE MOON?

:P

[DainBramaged]

39. WOW you missed it.....

[Confusious]

44. Didn't you notice it wasn't there anymore.............

Ooops, nevermind.

[Marr]

34. The anti-science crowd at DU really leaves me shaking my head.

I used to think it was only the right that was cursed with a magical wing, but unfortunately, that's not the case.

[phasma ex machina]

8. K&R

[hunter]

9. I think this is the only reasonable way to do it.

Using chemical rockets is like rowing a boat across the Atlantic. It can be done, but it's awfully hard on the passengers.

[walldude]

11. Twin Ion Engine Fighter.

T.I.E Fighter. Star Wars is becoming reality.

[bridgit]

12. Gerard O'Neill Lives!

His: The High Frontier, among others, advocated heavy ion pumps in deep space explorations for terra form-able systems http://orbitalhub.com/?p=399

4. Interplanetary Propulsion

Once a payload is in space, it is then eligible for interplanetary transport. The primary advantage of this is that the vehicle does not have to provide direct lift against the planet's gravity, so propulsion systems with thrusts much less than the vehicle's weights are quite acceptable.

4.1. Performance of Systems in the Literature

In this area, some concepts have already been sketched out which are intended to particularly exploit the capabilities of MNT. <6> examines lightsails, which are propelled by the light pressure from the sun on a large surface, and solar-powered ion engines, which turn solar energy into electrical power and use that power to accelerate ions to high exhaust velocities. (The accelerated ions are neutralized before release so that the vehicle does not build up a net charge.) As discussed, an unloaded sail 20 nm thick of aluminum will develop an acceleration of up to 0.16 m/s2, depending on its solar angle, at one AU from the sun. This is equivalent to a 0.08 m/s2 acceleration with a payload mass equal to the sail mass, or a 0.04 m/s2 acceleration with a payload mass equal to three times the sail mass. A major advantage of solar sails (built with or without MNT) is that they can provide this thrust continuously, without expending on-board reaction mass.

The ion engine discussed in <6> uses solar collectors with specific power on the order of nearly 105 W/kg to drive ion engines with a ~250,000 m/s ideal exhaust velocity, providing ~0.8 m/s2 acceleration. <2>, suggests the specific power could be more than an order of magnitude greater, and a 1,000,000 m/s ideal exhaust velocity vehicle could provide ~9.8 m/s2 acceleration.

http://www.zyvex.com/nanotech/nano4/mckendreePaper.html#RTFToC15

[jmondine]

17. There is another advantage to this: Simulated Gravity

By accelerating for the first half of the trip, rotating the craft 90 degrees, and decelerating the rest of the way, the astronauts would not have to be weightless for the entire trip.
As fun as zero gravity is, after long periods it takes a while to then get used to the Earth's (or Mars') gravity once planetside again. It also creates a hell of a lot of logistical headaches considering that anything you "set down", unless it's contained or adhered to a surface, can then float away and end up who knows where.

Arthur C. Clarke used this concept to great advantage in many of his books, including 2061 and Imperial Earth.

[Statistical]

27. However with current technology it would be a negligble gravity

Earth to mars in 40 days at constant acceleration would be 0.2114 m/^2.

1G = 9.8m/s^2
0.2114m/s^2 = 1/50th earth gravity.

To put it into perspective the moon micro gravity is 1.63 m/s^2 so it would be roughly 1/8th the gravity on moon.

However someday it pay be possible to increase the output of the engines to higher level of force.

A hypothetical ship w/ 0.6 G acceleration would not only provide gravity equal to mars for the trip but would go from earth to mars in 2 days!

[wroberts189]

20. In 24 hours a moonbase and trip to mars became feasable. knr/nt

[DainBramaged]

22. Yes, and it's interesting how science fiction is becoming fact now...

http://www.cybertech-systems.tcs-ltd.net/article.htm

[Greyskye]

24. If they find Helium-3 on the moon, it's even better than that.

NASA has said that more than just water was detected, but they aren't saying what yet. If they detected amounts of Helium-3, we've got a real game changer on our hands. Helium-3 is fusion fuel, and could not only power spacecraft, but could supply the energy needs of Earth.

http://www.space.com/scienceastronomy/helium3_000630.html

[Statistical]

30. Except we have no fusion reactor.

It is kinda like uranium was considered a contiminent in other mines until we got fission power plants working.

Having large supply of He3 is useful but useful only if someone gets a unity fusion reaction and that reaction uses He3.

[Greyskye]

38. If they find He-3, we will

And there have been lots of successful experimental fusion reactors over the years. http://en.wikipedia.org/wiki/Tokamak#Experimental_tokamaks

[Statistical]

42. You are getting the cart before the horse

1) We have He3 on earth it just is incredibly expensive due to scarity
2) While we have fusion reactors we don't have one that has reached unity. unity is power output = power input

So today is we had 10,000 tons of He3 on earth in 100% pure form it wouldn't matter because we don't have a reactor that outputs power (all current reactors require more power to sustain the reaction then they output).

Someday we may have a unity fusion reactor then the next step would be a reactor that outputs power (output > input) then next step would be scale up to commercial 1000 MW power generation THEN we would need a large. If we got that far and the power was cheap enough to compete with other forms of power and mining the He3 and transporting it to earth was cheap enough THEN He3 mining on moon would matter.

Having He3 today doesn't change that. We need the reactor FIRST then cheap source of fuel matters.

[Greyskye]

46. As you said yourself:

"It is kinda like uranium was considered a contiminent (sic) in other mines until we got fission power plants working."

If we have access to a large supply of He-3, that would provide an incredible amount of incentive. Countries and corporations will be climbing over each other in order to gain market advantage. I have confidence that the technology will follow.

Transporting anything from the moon to the earth is fairly simple. Rail-gun technology to get it out of the moons relatively insignificant gravity well, and it's all downhill from there. :)

[spin]

50. Big oil will stop that. (n/t)

[nemo137]

58. They won't be able to.

Sorry, this is one thing where I'm relentlessly optimistic, as alien as that is to my personality. There is a limited amount big oil will be able to do when the ball starts rolling on an advance like this.

[spin]

63. I hope you're right, but I'm a pessimist.

[edbermac]

26. Aye, we're having a wee bit of trouble with the ion drive, Captain!

[berni_mccoy]

33. A long-time friend of mine worked on Vasimr.

[stevedeshazer]

35. That is amazing, thanks.

May I recommend Commander Bunnypants for test pilot of the pre-beta version?



(with all credit due Swamp Rat)

[hunter]

56. Commander Bunnypants deserves a mission to Pluto and beyond.

These engines could do that.

[Better Believe It]

37. Let's go to Mars. Far more interesting. The moon? Been there, done that. K & R

[DFW]

40. I read about discussions on ion drives 15 or 20 years ago.

Apparently, they haven't quite gotten all the kinks out.

So much for my plans to run over to Australia for the weekend.

[backscatter712]

47. Oh, they've been making plenty of progress.

Ion drives have flown successfully on several space probes, and VASIMR drives have been built and are being tested in labs here on Earth.

The technology's incredibly promising!

[DFW]

51. I had heard about it a LONG time ago, but wasn't aware of any real progress.

If it is coming anywhere near to being efficiently being used for propulsion of space vehicles,
that is important news. Perfection of an ion drive, if it lives up to its potential (big "if,"
I understand), could mean the solution of manned inter-planetary travel. I haven't heard that
we're anywhere near there yet.

[backscatter712]

52. They're going to put on on the ISS next year.

It'll be a test bed, and it'll also have the job of reboosting the ISS periodically to keep it in orbit - it'll save tremendous amounts of money on fuel & resupply as the Progress resupply ships and Shuttle won't have to do the job with chemical rockets.

[DFW]

53. The issue about not having to ferry up fuel from earth is huge

This could possibly THE biggest single advance in the efficiency of propulsion technology, if it works.

[Statistical]

67. Just as small correction. you still need fuel just less fuel.

Ion engine for an equivelent amount of thrust requires <1% of fuel of conventional chemical rocket.

Of course the savings are not 99% because it also requires a substantial amount of electrical power so the engine is larger and more complex.

Still a substantial fuel savings is possible.

[hunter]

68. Someone in another thread suggested (tongue in cheek?) we could send the ISS to mars...

I apologize to whoever it was for not remembering their screen name.

In the old sort of ion engines the beam of high energy ions would eat away at components of the engine itself until it eventually failed.

This new engine design has fewer problems of that sort.

[backscatter712]

71. That's exactly the point of VASIMR.

IIRC, other ion engines had physical electrodes, which eroded over time until the engine failed, which is a huge problem in an environment where the nearest mechanic is millions of miles away.

The VASIMR, rather than using electrodes, charges the plasma up using radio waves. In other words, it's a modified microwave oven. And that design, once refined to the point where it's decently efficient, will ensure that the drive can run continuously for very long periods of time.

[Vincardog]

45. How do you give a continuous push for years, on a 39 day trip?

[BradXXX]

48. I think you have a problem with reading comprehension

All it says, is that it is possible for the continuous push to last for years. It doesn't say anything about needing years worth of continuous push to get to Mars. Apparently that only takes 39 days.

[backscatter712]

49. Very high specific impulse.

Specific impulse is a number that's akin to the "gas mileage" of a rocket engine.

Think of it as roughly analogous to the velocity of the rocket's exhaust.

Chemical rockets, while having very high total horsepower, have relatively low specific impulse. They have enough oomph to launch your spaceship from Cape Canaveral to earth orbit, but they're gas guzzlers, and they run out of gas in a few minutes.

VASIMR and other ion engines are the opposite. They have very low raw horsepower (think the amount of force a sheet of paper would give as it rests on your hand. But because the gas mileage, the specific impulse is orders of magnitude higher, instead of a fuel tank the size of an office building and compromising 99% of the rocket's mass, you use a fuel tank the size of a soda bottle, use tiny amounts of fuel at a time, and have it last you for months.

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

[nadinbrzezinski]

57. GEEKS of the world, you know Star Wars used Ion Engines extensively

right?

:-)

Yes science fiction does have some science in there...

[nemo137]

59. Yeah, but I think Lucas' knowlege of science was limited to whatever he heard in bars.

"Parsec? It sounds like a second, so it's got to be some kind of unit of time. Let's have Han say he made the Kessel Run in less than 12 parsecs."

::facepalm::

[nadinbrzezinski]

60. Well still a lot of the science in many of these fictional worlds

is real. Why a lot of scientists do silly things like oh advise these shows and movies.

:-)

Well the future nexus world also uses ION engines for in system drives.... and I do know what a parsec is.

:hi:

Shameless plug

Of course Star Trek has had an even closer relationship with the scientific community and it is a two way road.

[nemo137]

61. And there was a later explanation that Solo flew dangerously close to a black hole

making his overall journey shorter, thus making him the only person ever to make the Kessel Run in 12 parsecs.

But, yeah. I was raised by science and sci fi nerds, so I am well aware that scientists waste their precious time ;) advising them.

[HiFructosePronSyrup]

70. No, not really.

They had spaceships that looked like bowties, so they called them TIE fighters. Then later somebody invented an acronym to satisfy the nerds.

[Veruca Salt]

69. kick!