I've been following the discussion on the Lunar Space Elevator idea. While it sounds intriquing, I suspect we'll see a mass driver approach to delivering lunar...
8320
Ian Woollard
wolfekeeper
Jul 7, 2008 1:01 pm
... I think that for delivering goods and stuff *to* the moon, a lunar space elevator is really nice. You more or less just carry it to the L1 point on an ion...
8321
GWMobile
geopass2001
Jul 7, 2008 4:06 pm
What is impact of balloon assist on lower portion of space elevator cable. If you use a series of balloons to hold some of the bottom of the cable does it...
8322
Andrew Swallow
am4987
Jul 7, 2008 9:22 pm
... It would be practically no help. Lifting 15 miles of a 60,000 mile cable will reduce its weight by (15/60000)*100 = 0.025% The climbers would need extra...
8323
robert owen
craig_holm
Jul 8, 2008 2:55 pm
Given the overall length and mass of the cable, probably not. But what about balloon assist on the payload car?...
8324
climbach@...
muhstronomy
Jul 8, 2008 2:55 pm
I don't have my space-elevator books with me at the moment, but I don't believe this calculation is so simple. The 15+ miles of ribbon being held by balloons ...
8325
blturner3
Jul 8, 2008 4:32 pm
There are a number of other reasons that a balloon might be useful besides reducing the ribbon weight. But putting a balloon that high, that is big enough to...
8326
blturner3
Jul 8, 2008 5:57 pm
I should have said the atmospheric losses that adaptive optics can't correct for. Brian...
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Ian Woollard
wolfekeeper
Jul 8, 2008 8:40 pm
... No, it's trivial. The cable isn't significantly tapered over such a short distance even low down near the Earth. Fundamentally, the cable needs to be...
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Herbert Murray
hcm1955
Jul 12, 2008 8:42 pm
The balloon makes sense if the laser is space based. Then the climber could be lifted out of the atmosphere by balloon, where the laser can take over. This...
8329
Ian Woollard
wolfekeeper
Jul 12, 2008 11:11 pm
... You say, 'laser is space based' I say 'orbital space weapon'. You say 'avoid the problems of atmospheric effects' I say 'please don't shoot me'. -- -Ian...
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Kate H
kate_ropewalk
Jul 12, 2008 11:36 pm
Greetings, I'm a new member and I thought many of you would be interested in knowing about a film that highlights the space elevator. A new documentary film...
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Herbert Murray
hcm1955
Jul 15, 2008 12:45 am
Any laser useful for powering a climber, would be a very poor weapon. Any laser that would be a good weapon, would be useless for powering a climber (It would...
8332
Ian Woollard
wolfekeeper
Jul 15, 2008 12:56 am
... No, for a climber it wouldn't care too much, you can design it to take it pretty easily. But for the average thing on the ground, a laser like that would...
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Robert Munck
bobmunck
Jul 15, 2008 1:50 am
... Could you design it such that it wouldn't penetrate the atmosphere? A frequency that's absorbed by water vapor or carbon dioxide or methane, say? That...
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Andrew Swallow
am4987
Jul 15, 2008 5:26 am
... Planes could be fuelled by hydrogen. Only a few hundred major airports would need changing, unlike the millions of car gasoline stations. Cars suffer...
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Graham Addis
grahamaddis
Jul 15, 2008 7:50 am
... Methane?...
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Dan Ust
dan_ust
Jul 16, 2008 3:36 pm
I guess this would be both an engineering and financial problem -- but not an insoluble one. At first glance, though, wouldn't this require larger, sturdier...
8337
Jo Jaquinta
jim_plummer
Jul 16, 2008 6:02 pm
... I think the main problem is physics: energy density. Jet Fuel has an energy density of 42.8 MJ/kg (weight) or 33 MJ/L (volume). For hydrogen it would...
8338
Ian Woollard
wolfekeeper
Jul 16, 2008 6:07 pm
... Not sturdier, as the hydrogen is quite light, but they could look like this: http://en.wikipedia.org/wiki/Reaction_Engines_A2 ...
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Andrew Swallow
am4987
Jul 17, 2008 8:35 pm
... but not an insoluble one. At first glance, though, wouldn't this require larger, sturdier fuel tanks, making planes even heavier? ... Nice aircraft. I...
8340
Alexander Kawaihae
akawaihae
Jul 18, 2008 1:02 am
Hydrogen would a good substitute fuel, but it was tried over and over again around the turn of the last century thru the nineteen-thirties, but it was its own...
8341
John Barnes
kf4oyt
Jul 18, 2008 1:02 am
Space ElevatorHi, group... I mostly just lurk, and the exchanges here have always been very interesting. I saw an article on Space.com recently that NASA is...
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Ian Woollard
wolfekeeper
Jul 18, 2008 1:30 am
... Nah, it's not much more explosive than gasoline. Lots of rockets use it without too much problem in fact. It's fiddly to handle safely, but done routinely....
8343
Andreas
awnd329
Jul 18, 2008 1:39 am
At Mach 5 or higher it does not really make sense to push through the atmosphere. This is why the future of intercontinental travel is outside the atmosphere. ...
8344
Ian Woollard
wolfekeeper
Jul 18, 2008 2:11 am
... It pretty much isn't anyway. Supersonic aircraft fly very high, hypersonics, higher. There's hardly any air up there. ... If you mean rockets, no. ... No,...
8345
Andreas
awnd329
Jul 18, 2008 9:27 pm
... That makes sense. As you increase speed and altitude, though, isn't there a point somewhere when rockets become more efficient than jets? Is that point...
8346
Jerry Irvine
01rocket@...
Jul 18, 2008 9:41 pm
... Around 3-4. Also depends on what you call efficient, time to target or mpg. My experience with Hydrogen, and I have some, is the tanks are big balloons...
8347
Ian Woollard
wolfekeeper
Jul 18, 2008 11:14 pm
... It's a complicated question. As a rough rule of thumb, rockets work best at speeds around mach 8-12; and up, but are very inefficient below about Mach 5....
8348
Herbert Murray
hcm1955
Jul 19, 2008 12:36 am
I disagree, A climber that can take a laser hit that could take out plane, would not be very practical for a transportation system. I do agree that ther might...
