Elevators, Space, and War

On October 4, 1957, the successful launch and orbiting of Sputnik 1 inaugurated the Space Age. Since then, mankind has had a stop and start relationship with outer space. We've accomplished a great deal, but it's been expensive and risky.

The next stage of our expansion into the Solar System may be made a lot easier if space elevators can be built. No less a visionary than Sir Arthur C. Clarke has endorsed the concept. Brad Edwards, a leading space scientist, is actively promoting the effort, and a company called the Liftport Group has published preliminary plans [PDF] to design and build the first space elevator.

But -- as humans expand into space, will we take our warlike legacy with us? Last year, we wrote about the disquieting possibility of a space weapons race. Now, we have a new policy document that lays out the current U.S. administration's views on "defense and intelligence-related activities in pursuit of national interests."

The Presidential Directive on National Space Policy says that the United States will:

• [P]reserve its rights, capabilities, and freedom of action in space; dissuade or deter others from either impeding those rights or developing capabilities intended to do so; take those actions necessary to protect its space capabilities; respond to interference; and deny, if necessary, adversaries the use of space capabilities hostile to U.S. national interests; oppose the development of new legal regimes or other restrictions that seek to prohibit or limit U.S. access to or use of space.

The Directive goes on to say:

• Proposed arms control agreements or restrictions must not impair the rights of the United States to conduct research, development, testing, and operations or other activities in space for U.S. national interests.

There is a lot more in the document, and we encourage you to read the whole thing.

Mike Treder

Tags: nanotechnology nanotech nano science technology ethics weblog blog

Comments

[Tom Mazanec]

Nanofuture by J. Storrs Hall points out that a space elevator will eventually be struck by a satellite and broken. He proposes a accelerating launch tower just below orbital height and as long as Pennsylvania to do the trick.

[Tom Craver]

Once we get large scale space tethers, we won't need satellites other than geosynchronous - just hang whatever you want down from GEO on a tethered platform.

The day may come when non-geosynch spacecraft are prohibited.

[Tom Craver]

Regarding the directive - it looks to me like the difference between the new one and the old one ( http://www.fas.org/spp/military/docops/national/nstc-8.htm ) lies in the new one being phrased a bit more aggressively. The substance of our space policy doesn't appear to be greatly changed.

One exception is that the new directive seems to place greater emphasis on use of nuclear power in space, including potential commercial uses.

[Phillip Huggan]

Current Space Elevator bluep[rints call for the tether to be attached to a mobile ocean platform; a platformn that can be moved as necessary. Oscillations will travel up the ribbon and shift its location in orbit when a collision is impending.

[Phillip Huggan]

The existential threat of kinetic impacters (hitting Earth) launched from space ranks 6th or 7th on my extinction threat list. My favoured MNT administration involves patrolling Earth for low-temp/vacuum conditions. This would encompass the entire universe outside of Earth. Hopefully whatever military structures and technological solutions that are developed to mitigate Earth-based risks, will carry over to space.
Without GEO launch costs dropping below the current $10000/kg, there won't be any man-made threats originating from space (nor will we reap any benefits either).

Tom Mazanec or anyone else, do you know the tensile strength material requirements for Hall's tower? SE needs 35-45 GPa CNTs and we are presently stuck at 29 GPa. Is it a sci-fi mag-lev launcher? If so, good luck with that. You have like a few grams of magnetic material to work with for every few tens of meters of "rail-tower".

[jim moore]

Phillip,

According to Josh
"The "pier into space" is 100 km high by 300 long. Due to the curvature of the earth the center is bowed nearly 2 km away from a straignt line; the accelerator track on the top is nearly 5 km longer than the base (even though both end towers are locally vertical). The tower extends completely through the stratosphere (50 km) and mesosphere (90 km) extending into the ionosphere. The density of air at 100 km is less than one millionth that at sea level.

Compared to the skyhook, which is just barely possible with even the theoretical best material properties, a tower 100 km high is easy. Flawless diamond, with a compressive strength of 50 GPa, does not even need a taper at all for a 100 km tower; a 100-km column of diamond weighs 3.5 billion newtons per square meter, but can support 50 billion. Even commercially available polycrystalline synthetic diamond with advertised strengths of 5 GPa would work. Of course in practice columns would be tapered so as not to waste material; and the base of the tower would be broadened to account for transverse forces, such as the jet stream. Only the bottom 15 km (i.e. 15%) of the tower lies in the troposphere and would have to be built taking weather into account.

The electromagnetic accelerator along the top might be fairly heavy. In many designs, coils have iron cores; NASA's Marshall prototype weighs 100 pounds per foot. If we allow a tonne per meter, the total weight of the accelerator is 300 thousand tonnes. For comparison, the cruise ship QE2 is 70 thousand tonnes. However, most the weight is (relatively cheap) iron. Note that this entire weight, if it were concentrated in one place, could be supported by a column of currently available polycrystalline diamond less than 80 centimeters on a side."

[Phillip Huggan]

Hall's tower is contingent upon MNT (flawless diamond)? If so I withdraw my objection. The main reason the SE isn't viable right now is flaws (sidewall defects) in all present CNT manufacturing processes.

I'd be really interested in seeing CNT sidewall defect "healing" processes researched. I'm aware of two papers posted by someone in a Liftport forum thread, but that's all. Perhaps sidewall defect healing is what Brad Edwards is working on right now.

[Chris Phoenix, CRN]

Tom, one problem with geosynchronous satellites is speed of light lag. So you want things close to the earth.

You talk about hanging things down on a tethered platform--if you want to hang them within a few hundred miles of earth, that's almost as bad as building a whole 'nother space elevator for each satellite.

Of course, much of the reason for using satellites is simply that they stay up without using much additional power. High-altitude solar-powered aircraft might do as well as satellites for a lot of earth-related activities, once they're developed.

Chris

[Brian]

Nanofuture by J. Storrs Hall points out that a space elevator will eventually be struck by a satellite and broken.

There are legal and technical ways to dodge that problem. Another poster mentioned moving the base to induce wiggle in the ribbon. Edwards suggests shaping the ribbon in the regions where collision is most likely to avoid severing the ribbon.

Legal fixes to that problem might include protocols to determine who maneuvers to avoid the ribbon and so forth.

Compared to the skyhook, which is just barely possible with even the theoretical best material properties, a tower 100 km high is easy.

There are political and legal implications to a construction like that that might make it less than ideal. It's hard enough to get funding for a bridge when the construction spans multiple jurisdictions for example ...

I am not putting it down as unviable - believe me whatever it takes to make access to space a reasonable cost. Just pointing out that there are other variables than just technical.

[Michael Deering]

You say, "You talk about hanging things down on a tethered platform--if you want to hang them within a few hundred miles of earth, that's almost as bad as building a whole 'nother space elevator for each satellite."

Why do you use the term 'bad'? What would be wrong with Earth looking like a porcupine from space instead of a marble?

[Greg]

>>Why do you use the term 'bad'? What would be wrong with Earth looking like a porcupine from space instead of a marble?
<<

One problem is that Earth would not be porcupine-like, rather it would be mohawk-like (if you tilt your head the right way). That is to say that the beanstalks must be located on or at least near the equator. Why this is a problem is that there are any number of uses for satellites that just don't work well from an equatorial orbit (or its tethered equivalent). Satellites which require a ground track that covers the higher latitudes, and there are any number of satellites whose purpose requires this, cannot adequately be replaced by a bird hung off a beanstalk sitting on the equator.

Greg - Tethered platforms could still swing north and south - they don't have to hang statically at the equator.

Another solution is to actually tether them to the ground at a higher lattitude - that adds a bit more strain on the tether, but it's not too much greater.

[Greg]

>Tethered platforms could still swing north and south - they don't have to hang statically at the equator.
Another solution is to actually tether them to the ground at a higher lattitude - that adds a bit more strain on the tether, but it's not too much greater<

I am not sure that you can, practically speaking, move the latitude enough to make a difference (if you have worked the numbers on this indicating otherwise, I would be interested to see it).

[michael Laine]

hi, i sent you a personal email to your crn address, but wanted to add something here.

i have gone on record several times, stating a lack within industry, and a lack within the government of having clear, safe-worker, standards for employees, when working with carbon nanotubes. i worry about this, not just as it relates to our project of the space elevator, but also as its impact on a global workforce.

i'd like to post 2 links, one to the (video)presentation i made to the wilson center on nanotech, and the other is our policy on public inclusion. we strongly beleive this needs to be a global project.

take care. mjl

http://www.wilsoncenter.org/index.cfm?fuseaction=events.event_summary&event_id=185117

http://www.liftport.com/index.php?id=190

[Chris Phoenix, CRN]

Michael D, I meant "bad" in an engineering sense, as in too difficult/costly. The point of a space elevator is to make space access easy and inexpensive. But you don't do that by building a space elevator for each satellite!

Chris

[Tom Craver]

For some info on off-equatorial elevators, see:

http://www.mit.edu/people/gassend/publications/NonEquatorialUniformStressSpaceElevators.pdf

[Greg]

Tom the url you posted was truncated and hence did not link to the info you were trying to link to. Could you try again?

[Tom Craver]

Hmm works for me - maybe it's your browser?

Here it is split in two parts - copy past both!

http://www.mit.edu/people/gassend/publications
/NonEquatorialUniformStressSpaceElevators.pdf

[Mike Treder, CRN]

META:

Re the linking issue above, anyone posting comments here is allowed to use basic HTML, so Tom's link can be shown as this [PDF].