Yes the space elevator guys are at it again. It's interesting that they figure they can do this little project of theirs making a buck as they go. If they can do it I will be in complete awe of how incredible the feat would be.
Let's be honest though folks. A space tether stretching up over 62,000 miles? (By the way is that number really right or did they just accidentally add three zeros?) They are certainly aiming big if that number is right. You're talking about a space tether above Geo-synchronous orbit. Which brings to mind another question: Why above geo and not at Geo? The whole advantage I thought of having a satellite at Geo levels of altitude was that the period of your orbit was exactly 24 hours. This means you have a satellite at exactly the same point in the earth's sky 24 hours a day 365 days a year. If you're above you start to go slower than the period of rotation of the earth so wouldn't the satellite attached to the tether get dragged along?
Either way this is getting a little far fetched. I'll believe it when I see it. Until then I still think conventional chemical rockets are the best way to go.
I would guess outside geo would account for cargo and counter weight
ReplyDeleteExactly correct anonymous. The portion above GEO holds up the portion below. The center of mass of the entire system is just slightly above GEO, in order to maintain tension throughout - if it was balanced right at GEO, then it would not be under tension, and wouldn't be capable of lifting any cargo. It is the ultimate Indian rope trick - except it wouldn't be a trick, it would actually work; the math is sound.
ReplyDeleteSuch a system would bring cost to orbit down from >$2600/kg (Falcon V) to under $1 per kilogram. The SpaceRef article has one slight error near the end though... it says that mechanical lifters would move both up AND down the ribbon. They would only go up, and release any cargo somewhere along the length of the ribbon (below GEO to go into earth orbit, above to go elsewhere), after which the lifter would travel further up the ribbon and become more counterweight.
And yes, they would be capable of making a profit - any company producing Carbon Nanotube sufficiently strong (>65GPa) and in sufficient length to make a ribbon (>100000km long) could also make nanotube fibre for building suspension bridges, weave them to make automotive parts stronger than steel but lighter than paper, and so on.