DailyDirt: I'm Givin' Her All She's Got, Captain…

from the urls-we-dig-up dept

Space travel is filled with all kinds of complex challenges — microgravity, radiation exposure, fuel constraints, etc. Thankfully, engineers and physicists are coming up with creative solutions to some of these problems, and new propulsion systems are being put through a battery of tests to verify their safety and reliability. Here are just a few cool propulsion designs (that may or may not work at all).

If you’d like to read more awesome and interesting stuff, check out this unrelated (but not entirely random!) Techdirt post via StumbleUpon.

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Comments on “DailyDirt: I'm Givin' Her All She's Got, Captain…”

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Kal Zekdor (profile) says:

Propellent-less drive?

A propellent-free drive is a major milestone for sustainable space travel.

In a zero-g vacuum, the only (tested) means of self-locomotion is to expel some manner of matter in the opposite direction than you want to travel. The problem is, matter is hard to come by in space. Energy, however, is fairly easy to obtain if you’re anywhere near a star. However, as far as I know, there are no means of converting stored energy into thrust, without also expelling matter. So while energy can be restored in situ, and can be used to augment the thrust gained by matter expulsion, at the end of the day, something is coming out of your thruster. Which means that, eventually, you will run out of that something.

I’m skeptical, but if this thruster pans out, it would be a major breakthrough in sustainable space travel.

Personally, though, I’d put my money on solar sails.

JoeCool (profile) says:

Re: Re: Re: Propellent-less drive?

Incorrect. Solar sails use the radiation pressure of light to operate. Other common names for solar sails are light sails and photon sails.

One of the more common design proposals is to have a laser in orbit that “pushes” craft using solar sails rather than rely on the light the sun. Laser beams are more highly focused, so provide more radiation pressure.

So my suggestion was to put the laser on the craft instead of in orbit. 😀

Beta (profile) says:

Baloney detector pegged

The “Cannae Drive” is not absolutely impossible — nothing in science is — but I’d offer long odds against it. for one thing:

“…If it really works, it could be a major breakthrough for deep-space exploration.”

If it really worked, we’d have to tear down our theories of Physics and rebuild them. Ms. Nelson doesn’t seem to understand just how staggering this discovery would be if it turned out to be real, so I have to doubt that she asked the right questions about this experiment. (And NASA has never had much of a reputation for experimental physics, even before they started losing spacecraft by e.g. getting miles and kilometers mixed up.)

Anonymous Coward says:

Re: Baloney detector pegged

and what if our theories about physics actually are wrong? or at the least much more incomplete than we believe?

Just because something defies the current knowledge is no reason to proclaim it is impossible. Test it, analyze it and find out if it actually works. and if it does work against all expectations, it is time to go over the theories again.

Anonymous Coward says:

Re: Baloney detector pegged

While I agree with your assessement that there are very long odds against a device that violates conservation of momentum,I have to call baloney on your closing statement.

NASA did not lose a spacecraft by getting miles and kilometers mixed up. A (supposedly unimportant) piece of software that was supposed to be calculating total thruster impulse in newton-seconds was actually calculating it in pound-seconds. The results, when fed into the trajectory prediction calculations, produced weird answers that no one could quite understand. This caused the navigation team to incorrectly calculate the location of the spacecraft. The course went too deep into the atmosphere, resulting in destruction of the spacecraft.

Expunging inches and pounds from the face of the earth would still be a good idea …

Beta (profile) says:

Re: Re: Baloney detector pegged

Scientific theories posit that certain things are impossible — otherwise they’d be useless. But the scientific method requires that all theories be subject to challenge, that no theory can ever attain the rank of “absolutely certain”, that we always remain open to the possibility that our most trusted theories might turn out to be wrong. In that sense, nothing in science is absolutely impossible.

Anonymous Coward says:

Re: EmDrive Not Proven Yet?

I bought the full text of the article, and it’s a bit more complicated than the summary would suggest.

Essentially, the Cannae thruster is a long pipe that bulges in the middle into a “pillbox” shape. Cannae’s design calls for radial slots to be carved into one side of the pillbox, but not the other; according to Cannae’s theories, this assymetry is what produces the thrust.

Because NASA employs actual scientists, they performed three separate experiments: one with the slots, one without the slots, and one with a 50 ohm resistive load. The slotted and unslotted thrusters both produced significant thrust, and the thrust differed by less than 2%. The resistive load did not produce thrust.

The tests with the RF load strongly indicate that there was nothing wrong with the apparatus; the thrust that they detected seems to be actual thrust. On the other hand, because the slotted and unslotted thrusters both produced the same amount of thrust, it seems that Cannae’s slots have nothing to do with why the thruster works.

They clearly need to do more tests, but the results so far indicate that the thrust is real. It’s just that Cannae’s theory as to what produces the thrust is demonstrably incorrect. There’s currently no good theory as to why this works, which is why scientists are getting excited.

rpenner1886 (profile) says:

Re: Re: EmDrive Not Proven Yet?

I disagree. It is not “thrust” that is demonstrated but a signal from an apparatus which is designed to measure “thrust” if it exists. However, the questions not well explored in the paper is what else might contribute to this signal, and how the signal varies as a function of frequency, power and atmospheric pressure.

Francis Bacon: Knowledge is power.
Ben Parker: With great power comes great responsibility.
Carl Sagan: Extraordinary claims require extraordinary evidence.

It seems we have the extraordinary claims and a paucity of extraordinary evidence. The paper doesn’t even come with error bars.

Anonymous Coward says:

Re: Re: Re: EmDrive Not Proven Yet?

Measuring a vacuum thruster as it varies with atmospheric pressure would seem to be counterproductive. The tests were run at 5x10E-6 Torr, or 6.58x10E-9 standard atmospheres. LEO runs around 10E-9 Torr, so they’re doing pretty well.

They obviously need to perform further experiements. I personally doubt that they’ve actually found a workable vacuum thruster, but it doesn’t matter. The point is that, in response to the parent post, the experimenters used two separate controls. They measured thrust with one of the controls, but not with the other control; this is far, far more interesting than measuring thrust with both controls.

alternatives() says:


. Is it April Fool’s day every day?

What skin is it off my teeth if someone tries this idea?

we’d have to tear down our theories of Physics and rebuild them.

And that matters how? If the theories were wrong, they were wrong. It would not be the 1st time. Is there some kind of hazard to this tear-down that should be shared?

Mason Wheeler (profile) says:

Re: Re: And?

You kidding? It’s pretty much every scientist’s dream. There aren’t very many scientists who are household names, but one of them, who pop culture tends to regard as more or less the smartest man who ever lived, was the last guy to find a problem with Newton’s laws: Albert Einstein. Who wouldn’t want to be remembered in his company?

Urgelt (profile) says:

EM Drive Not Proven Yet?

My two cents.

1. The measured thrust was teeny-teeny-tiny. Which means that to avoid measurement errors, you have to go to great lengths.

2. The experimental set-up only took a few days. They did *not* go to great lengths to avoid measurement errors. (They did a few things to minimize measurement errors, but obviously did not spend much time worrying about it.)

3. The null case – a configuration not expected to produce thrust – was measured to produce about the same thrust as the EM Drive configuration. That’s *strongly* suggestive of measurement error.

4. NASA’s paper doesn’t deal with theory behind the EM drive at all. It’s just a report of an experiment hastily thrown together which produced unexpected results (e.g. null case wasn’t null).

5. And then… despite the haste, despite the very small ‘thrust’ measured, despite the null case being the same as the EM case, despite the utter lack of grappling with any theory whatsoever, the NASA experimenters announced ‘success.’

That’s really sloppy work.

Sooner or later, NASA’s front office is going to stomp on those guys. They’re an embarrassment.

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