NASA Studying Solar Powered "Space Tugboat" 86
Zothecula writes "Last year, NASA announced it was seeking proposals for mission concept studies of a high-power solar electric propulsion (SEP) system that could be used in a 'space tugboat.' Such a ship would be used to ferry payloads in low Earth orbit (LEO) into higher energy orbits, including geosynchronous Earth orbit (GEO) and Lagrange point one (L1) — saving on fuel and the use of expensive secondary boosters. NASA also anticipates an SEP system could be used to propel spacecraft into deep space for science missions and for the placement, service, resupply, repositioning and salvaging of space assets by commercial operators."
Sigh (Score:5, Insightful)
Welcome to the 1970s? Solar panels + some kind of high ISP, extremely low thrust engine (used to be ion engines but apparently casamir effect thrusters are much better) have been planned ever since.
The problem is really simple. It's cheap to study a potential space travel mechanism on paper. But you cannot make any real progress unless real hardware is built and tested in space. And that costs a fortune, because a kilogram in space costs about $10,000 to get it there. Not to mention costs other than money, such as time and launch windows and delays and so forth.
SO...a rational person at NASA, if the organization was not at the mercy of Congress for every project, would dedicate ALL of their budget to getting that $10k/kilogram cost down to something affordable. Even if this took a large up-front investment to solve this problem.
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SO...a rational person at NASA, if the organization was not at the mercy of Congress for every project, would dedicate ALL of their budget to getting that $10k/kilogram cost down to something affordable. Even if this took a large up-front investment to solve this problem.
But...but what about the moonbase they were supposed to build?
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Welcome to the 1970s? Solar panels + some kind of high ISP, extremely low thrust engine (used to be ion engines but apparently casamir effect thrusters are much better) have been planned ever since.
The problem is really simple. It's cheap to study a potential space travel mechanism on paper. But you cannot make any real progress unless real hardware is built and tested in space.
That stuff is like, old, man.
http://en.wikipedia.org/wiki/Ion_thruster#Operational_missions [wikipedia.org]
I know for a fact the wikipedia list is only NOTEWORTHY unusual historical missions involving ion electric engines, not every boring little comsat that has yet another station keeping system.
Re:Sigh (Score:5, Interesting)
Might be smarter to attempt to 'surf' the planet's electromagnetic field.
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SO...a rational person at NASA, if the organization was not at the mercy of Congress for every project, would dedicate ALL of their budget to getting that $10k/kilogram cost down to something affordable.
Which translates to "more power (and money) to SpaceX and co.", I assume. I just wonder how much money has been spent on that Constellation nonsense.
Re:Sigh (Score:5, Insightful)
SpaceX has spent less money to get actual rockets to orbit than NASA spent to build a launchpad. Perhaps privatization isn't always better, but apparently in some cases it works incredibly well. Privatizing something is a bad thing, I think, when you are essentially having government give a private entity a natural monopoly. Hence, privatizing the power grid, etc.
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Yep, it's all about competition. If the government can foster competition between multiple companies, then it usually works out quite well. If it just hands a monopoly to some corporation, it usually turns out to be a disaster because the company isn't answerable to the taxpayer the way the government is, and having a monopoly doesn't care about keeping customers happy. So if something needs to be a monopoly, it's really better to just have the government do it directly, preferably through an autonomousl
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Unfortunately, the teabagger types seem to think that "government = bad, corporation = good"
Careful, your insipid bigotry is showing.
so they want to privatize everything regardless if there's any competition at all.
If only there were evidence for this assertion. Demonizing political opposition is a favorite past time on Slashdot, but it rarely hits the mark. But as it turns out, there are a lot of perils in privatization.
Failures of privatization can sometimes be traced to a market that naturally lacks competition, such as the electricity grid, but more common causes of failure are forced actions, artificial scarcity and abundance, or rent seeking.
For example, California
Re:Sigh (Score:5, Insightful)
Ion thrusters have a distinct advantage over Casimir effect thrusters in that the former actually exist.
For LEO to HEO I think tether propulsion [wikipedia.org] is a far better candidate.
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Have we not actually found a material that enables the construction of a space elevator in graphene though, which would reduce the costs to orbit to a tiny fraction of what they were previously? Yes spinning it out to the correct length is a serious engineering challenge, but its not physically impossible. And for the record, I was one of the greatest sceptics of space elevators until I heard about graphene.
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How about a tension-leg platform that is made to be lighter than air by large rigid balloons that contain a vacuum?
That way no unobtainium is needed. Just have to figure out how to deal with the very high winds in the upper atmosphere.
Doesn't go far enough (Score:2)
Doesn't go nearly far enough. Just getting up through the atmosphere is not really the point. Balloons do that pretty well. The trick is to build a tower so high that
it reaches geostationary orbit, so the top of the tower is in orbit, not just in space. That's about 36000 km up.
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The top of the tower needs to be higher than that. With something large and heavy up there.
You want a counterweight above GEO so that the station at GEO isn't dragged down into a spectacular crash.
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How about a tension-leg platform that is made to be lighter than air by large rigid balloons that contain a vacuum?
That way no unobtainium is needed
Except for the unobtanium that you'll be constructing the balloons out of.
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Except for the unobtanium that you'll be constructing the balloons out of.
I was thinking about something like this.
http://www.liquidmetal.com/ [liquidmetal.com]
Twice the strength of titanium and is able to be molded like plastic. I thought I remember them saying that they were able to produce finished products that are accurate down to the micron, but I don't see that on their site anymore.
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Twice the strength of titanium and is able to be molded like plastic.
Do you really think that that material will be both (a) strong enough to keep from collapsing/imploding due to the air-pressure differential and (b) light enough to stay aloft, i.e. lighter than the equivalent volume of air?
It would be cool if it was, but I'll believe that when I see it.
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large rigid balloons that contain a vacuum
This is a very hard design requirement. You'd be better off with hydrogen filled balloons that have a lot less structure to them. And even with perfect unobtainium balloons, you'll only float to about 100-150km, the limits of the buoyant part of the atmosphere. As another poster noted, you need to get past 36,000 km. That's not going to happen even with magic balloons.
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The problem isn't really height, it's speed.
With a space elevator you get up to speed over a few days as you move up the elevator. At geosynchronous orbit (which I find from Wikipedia is actually 42k km), you are traveling exactly the speed you need to go to stay in that orbit. And somewhat lower altitudes, you can enter lower orbits though you might want to circularize it somewhat.
The most energy efficient launch would probably involve taking a balloon up a hundred km or so, then accelerating hard horizontally with a scramjet.
No, it wouldn't be. You have energy loss due to air resistance and work done in accelerating the mass of the remaining propellant in the scramjet. The most energy efficien
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Yes, we have a material that barely meets the required strength to be self-supporting with reasonable taper.
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Casamir effect thrusters? (Score:5, Informative)
Do you mean VaSIMR?
http://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_Rocket [wikipedia.org]
Or Hall Effect Thrusters?
http://en.wikipedia.org/wiki/Hall_effect_thruster [wikipedia.org]
And Ion Thrusters of various types have been used as primary propulsion n space successfully ever since Deep Space 1. They've been used for satellite orientation and station keeping for decades. They are vastly more efficient than chemical thrusters, reducing the amount of propellant you need to carry, and therefore reducing launch costs.
Re:Sigh (Score:4, Insightful)
The problem with reducing launch costs is there's only a couple ways to really do that. One is to improve existing rocket tech and costs, the way SpaceX and others are doing with privatization. That might help some, but you're not going to get order-of-magnitude or better improvements out of that approach, because the laws of physics and the cost of fuel put big limits on just how cheap you can make launching that way.
The second way is to build a space elevator. Of course, we're still in the phase where people are laughing about it instead of doing it, because the idea seems too far-fetched for morons^H^H^H^H^Hlaypeople, and also because it relies on a material that's extremely new and not yet proven in industrial applications. Even with graphene or carbon nanotubes or whatever, the initial cost will still be extremely high, and you know how short-sighted humans are with economics (they'd rather pay much more over a long term than pay a big up-front cost and spend less over a long term; that's why they get loans for everything and buy subsidized cellphones).
Another way is to follow Newt's idea and build a moon base. (I can't believe I'm defending Newt here; the guy is a scumbag, but just like a stopped clock is correct twice a day, he's right about the moonbase, though I have no idea how he proposes to pay for it since he, like every other non-Paul Republican, wants to maintain giant military expenditures and start a war with Iran to boot.) With a moon base in place that has manufacturing facilities, researchers on Earth would be able to send stuff to their colleagues on the moon base to be manufactured and tested either on-site or in space. The launch cost for anything from the lunar surface would be dirt cheap compared to here, because of 1/6g gravity. Of course, that's only once you have the base in place and fully stocked with equipment, and able to mine and refine materials and energy or fuel from the lunar surface. Getting to that point will probably cost a lot more than building the space elevator (just guessing), but it can be done with present technology mostly, and would have some other additional benefits as far as providing us experience in sustaining human life off-world.
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Launch from altitude make more sense than any of those.
Substituting fairly cheap fuels and reusable lift vehicles [wikipedia.org] to bring your space craft [wikipedia.org] to 50-70,000 feet reduces costs and risks substantially.
Expensive space fuel requirements are drastically reduced, as you are burning Jet A to get to launch altitude.
Lets face it, space elevator is not happening any time soon, and moon base is loony-tunes until we have better lift capability. We can barely keep the ISS manned at this point. Getting any amount of buildi
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Getting the infrastructure in a "moon base" to build and launch anything significant will be difficult and far off to say the least.
Really the only option that has been put forward that even has some realism is the space elevator, and even that is pretty fantastic.
When it comes down to it, the reason it is so impractical is A) it is so big and would require X amount of resources to physically build, and B) the dimensions being so big that no current material would be able to withstand the stresses required
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When it comes down to it, the reason it is so impractical is A) it is so big and would require X amount of resources to physically build, and B) the dimensions being so big that no current material would be able to withstand the stresses required for construction. You mention nano-tubes and graphene (and I recall something called buckyballs, which might just be something about carbon nano-tubes), but the problem with those right now, is to make the amount required for even a hairs strand is very hard to do
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The problem is really simple. It's cheap to study a potential space travel mechanism on paper. But you cannot make any real progress unless real hardware is built and tested in space. And that costs a fortune, because a kilogram in space costs about $10,000 to get it there. Not to mention costs other than money, such as time and launch windows and delays and so forth.
Cheap to study indeed. From the announcement:
Following the announcement, NASA awarded five companies four-month study contracts totaling approximately US$3 million, with a maximum individual contract award of $600,000. The selected companies were Analytical Mechanics Associates, Ball Aerospace & Technologies, Boeing, Lockheed Martin, and Northrop Grumman. Each company is tasked with providing a final report that will help identify technology gaps and look at possible solutions using SEP systems.
$3 million spread among 6 companies is not serious money. It actually sounds like "lets keep Joe on the payroll" money. Money to keep a company interested and a few scientists (maybe 5 or 6 per company) employed till there is something "real" to do. (Not that I think that is a bad idea in general, scientists have to eat between big projects, especially if you want them to stick around and not wander off to some other industry.).
But I don't think this is serio
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SO...a rational person at NASA, if the organization was not at the mercy of Congress for every project, would dedicate ALL of their budget to getting that $10k/kilogram cost down to something affordable.
Quick correction: It's actually down to a price of ~$2k/kilogram with the SpaceX Falcon Heavy [wikipedia.org]. That's still a fair bit of cash, but somewhat reasonable compared to the cost of developing a payload.
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The same Atlas V can transport about 5 times as much to LEO as it can transport to GEO. [wikipedia.org] A space tug could transport a satellite from LEO to GEO. The cost for this is mostly in bringing the tugboat into space. Since the ion drive needs only small amounts of propellant the running cost is pretty low.
The tugboat reduces the cost of a transport to GEO to the cost for LEO (which is just 1/5th) plus the cost for the tug. This can save a lot of
Electricity source (Score:2)
Re:Electricity source (Score:5, Informative)
The sterling engine work that NASA is doing is to make the RTGs more efficient - this is not for propulsion but for providing power to other systems on the spacecraft (avionics, transceiver, instruments). Part of the motivation is to reduce weight, or to get more power for the same amount of weight. The other issue is that the isotopes which are commonly used for RTGs were byproducts of nuclear weapon production, hence, have not been produced (in America, at least) for decades.
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The sterling engine work that NASA is doing is to make the RTGs more efficient - this is not for propulsion but for providing power to other systems on the spacecraft (avionics, transceiver, instruments). Part of the motivation is to reduce weight, or to get more power for the same amount of weight. The other issue is that the isotopes which are commonly used for RTGs were byproducts of nuclear weapon production, hence, have not been produced (in America, at least) for decades.
The thing is that the Stirling engine does not care where the heat comes from, and its efficiency is higher than the efficiency of even good solar cells. I just wonder how well would a solar-heared Stirling fare - mass-wise, compared to solar cells - for power output in the 100KW-1MW range.
A tugboat (Score:2, Insightful)
with nothing to tug?
one would have to get shit into space for a reasonable cost before shuffling it around would be an issue
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just put a winch on it and drop a hook down to earth.
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It'd be a good place to listen to Rasta dub music, mon. Not to mention the occasional need to move stuff around Freeside.
In Another Newsflash (Score:3, Funny)
Dr. Einstein - a german patent clerk - has declared a galactic speed limit. It is estimated that this limit will extend our whale oil supplies well into the next decade.
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299792458 m/s. It's not just a good idea... IT'S THE LAW!!!
Technical Question (Score:5, Funny)
How will this work at night?
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How will this work at night?
You'd simply have to line the spaceways with construction lights like they use on freeway work. Just make sure to put them out the day before they are needed. Otherwise its lights all the way down.
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Ahh! Makes sense. They might need some kind of electric tug to put them in place. Has anyone suggested this to NASA?
maybe invent a (Score:5, Interesting)
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reasonable engineering and physics make it entirely possible for a construction in orbit to be able to capture low orbit junk, compress it and then jettison in a trajectory that would take it to the sun if provided enough energy to escape the Earth's gravity and get picked up by the sun's.
You say that as if it were a trivial problem, it isn't.
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Reasonable engineering certainly does not.
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Silly question, but assuming that the minuscule mass of objects in low Earth orbit still contribute to the Earth's overall mass with respect to the inertia and centripetal acceleration that keeps us in orbit around the sun. If we were to start ejecting tons of crap from LEO and sending it towards the sun, however minute the volume, couldn't we potentially alter the balance slightly and possibly even impact our orbit (duration / trajectory / stability) ?
I'm guessing no, but that assumes everything in modera
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I haven't done the math, but I think you'd have to eject something roughly the size of Australia for the effect on Earth's orbit to even be measurable.
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Silly question, but assuming that the minuscule mass of objects in low Earth orbit still contribute to the Earth's overall mass with respect to the inertia and centripetal acceleration that keeps us in orbit around the sun. If we were to start ejecting tons of crap from LEO and sending it towards the sun, however minute the volume, couldn't we potentially alter the balance slightly and possibly even impact our orbit (duration / trajectory / stability) ?
I'm guessing no, but that assumes everything in moderation.
No, because the centripetal acceleration is due to gravity, and is therefore independent of the Earth's mass. The gravitational force on an object is proportional to the object's mass, and therefore the resulting acceleration due to gravity is independent of its mass. Thus "inertial mass" and "gravitational mass" are equivalent, and moreover, the effects of being in a gravitational field are completely equivalent to being subject to acceleration. It is this realization that Einstein described as the "hap
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Nah, fire it at the moon, so when Newt gets there he can use it to build a shelter ;)
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Yes! (Score:5, Interesting)
This is exactly the kind of basic space infrastructure NASA should be working on. Space tugboats, construction vehicles, mining drones and assayers, cargo haulers, all the simple stuff that makes a civilisation run smoothly. We need to walk before we run, and that means mastering the basic techniques of constructing and operating these types of vehicles long before any thought is given to colonising the moon or Mars.
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Absolutely. As commercial ventures start to make the trip to LEO cheaper, what NASA should be doing is working on basic technology to enhance what we can do once we get there. Like use LEO (halfway to Mars in terms of delta-v) as a staging point for a mission beyond.
This is the kind of thing that makes me feel good about NASA's future.
Loony-Tunes Flashback (Score:2)
Some toot high, and some toot low,
But the toot-toot-toot don't mean a hoot,
It's the chuga-chuga-chuga that makes 'em go!
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I question your numbers. I believe 200W/m^2 is reasonably accurate on Earth's surface, but conditions are entirely different in orbit, where you don't have an atmosphere, cloud cover, etc. reducing your solar efficiency.
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Very little difference, I think.
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It will run on a single torch battery. My indifference has paid off, as usual.
All for the idea but not for the approach (Score:1)
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I was wondering when the obligatory Mission Earth/Tug One reference would surface.
Asteroid Mining (Score:1)
What we need to do is to move the Eros asteroid o where we can smelt all those metals (including a lot of gold) into pure form, then get them all back on earth (without accidentally killing ourselves or the planet.) There's probably enough precious metals in it to literally pay off the national debt.
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Smelt them on Eros, or build an induction catapult on Eros to process the metals somewhere else. But my bet is on building the processing plant in low earth orbit, flying it to a near earth asteriod and producing metal products on site.
Tubgoat? (Score:2)
I read the title as "Tubgoat" and thought, as any normal person would, that it was about something like Tubgirl, but.. worse.