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Blimps... In... Space...
LandGator writes "MSNBC reports a California company with an alternate launch site in Texas, JP Aerospace, is on their third test of a blimp system specifically designed to fly to space. Blimps. To Space. At payload costs around a dollar a ton to LEO. Their concept, first unveiled at the Space Access '04 conference in Phoenix last month (with a blog report here, include the Ascender, a ground-to-near-space blimp, which docks to a helium-inflated two-mile-long station at the edge of space, over 20 miles up. Another ship, also a blimp but specifically designed to reach orbit, takes the payload from there to LEO, using well-proven electric propulsion (AKA 'ion drive'). That trip to LEO would take up to nine days, but that's a good thing; for, what goes up fast, must come down fast, and speed is energy which must be bled off by either massive amounts of expensive and explosive rocket fuel, or through ablative heat transfer which has its own problems (as we have seen before). JP Aerospace has flown many PongSats -- micropayloads the size of a ping-pong ball -- for balloon or rocket-launch. Over 1,500 PongSats have flown to date, which demonstrates a track record in near-space few of the X-Prize contenders can approach. Oh, yes, the Air Force is interested."
Incase there are actually people not reading the linked article, the interesting part is quoted here:
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uhm... no. hydrogen is 1/4 the weight and therefore has ((airdensity)-(heliumdensity))/((airdensity)-(heli umdensity/4)) the buoyancy. In this case the density of air is so much higher that the increase in buoyancy isnt even 25%, let alone the 300% you say.
Half the weight. Hydrogen is diatomic.
The Hindenburg was filled with hydrogen, not helium. Hydrogen burns, helium does not. Besides, the Hindenburg was painted with some rather flammable compounds..
Well, let's work it out. Assuming an ion Drive can produce a net thrust of 0.01g (.0931 m/s). LEO is around 7600m/s. That gives 81362 seconds, or 22 hours. Obviously they're planning on much lower accelerations than even that, but low forces build up over time.
TODO: Something witty here...
Although the Hindenburg is often perceived as an advertisement against hydrogen, it was, in reality, more of an advertisement against using cellulose nitrate or cellulose acetate to add rigidity to the skin of a dirigible.
In all likelihood, it was the flammable nature of the skin that led to the ignition. Sure, having all that hydrogen there didn't help once the fire started, but there were a lot of successful hydrogen-filled blimps and dirigibles up to that point (the survival ratio was at least as good, if not better, than that of hydrazine or solid-propellant rockets).
Eloi, Eloi, lema sabachtani?
www.fogbound.net
Your question begs multiple misconceptions.
First, escape velocity is about getting you permantly out of earths gravity well. Not something you want if your destination is a stable orbit around the earth.
Second, escape velicity is a ballistic value, ie. the speed required to kick your butt off the planet from ground level going straight up.
Third, pushing "a big inflated condom" around in the upper atmosphere is not really a problem since there isn't much air to create drag.
Further, the higher you go, the less drag you feel, hence the "launch" of the orbiter from a platform already 20 miles up.
-- The morphemes of your disquisition are ascertainable, but they have eschewed an ambit of transpicuous exposition.
That is what the ion engine is for. They calculate it will take 9 days to acclerate the craft to 8km/s.
Thank you. The stupid Hindenburg was the begining of bad science in the media. Due to the radio reports and the worldwide viewing of the recorded images of the disaster no formal inqury into the cause of the disaster was done. As we know now the skin of the Hindenburg was painted with what was essentially ROCKET FUEL. A small static discharge along a seam is the most likely cause of the disaster, the skin almost exploded and it wasn't until much later in the disaster when the envelopes tore open due to loss of internal structure that the Hydrogen had any affect on the fire. Not only that but no people were hurt by the hydrogen fire because due to hydrogens boyancy it would have risen to the top of the structure and burnt there.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
This is stupid, I swear noone has any vision.
First, they're talking about 20 miles up for this two-mile 'lily-pad'. At 20 miles, we still have atmosphere, so we still have buoyant(sp) forces acting. Since there's a buyoant(sp) force at work, orbital mechanics can be damned. Your airship doesn't fall back to Earth because it's lighter than air.
Are you with me, then? You have a lovely two-mile long launch platform. From here, you launch another, smaller balloon with even less density and a few ion engines. This smaller balloon floats up as high as the remaining atmosphere allows. At this point, we'll say that the balloon is 'floating' on the very top of the Earth's atmosphere. It won't go down (buyoant[sp] force) and it won't go up (gravity). At this point, as long as the ion engines can beat the force of gravity, you have acceleration.
Acceleration, even small amounts of it, mean a lot in a vaccum. Give it a couple weeks and you'll find yourself speeding along at 8 km/s. Let go of the object you want in orbit and use the same ion engines to slow down. Physics being what they are, you should wind up back where you started with the same amount of velocity as when you left. At which point, you'll be 'floating' on the top of the Earth's atmosphere and you can manipulate your airship to get back down to the 20-mile-high 'lily-pad'.
So, yeah, you're right it's leaving, but it's also being replaced by natural radioactivity so that even after all the hydrocarbons are used up, natural gas wells will still be producing helium for millions of years.
According to Praxair, fifty percent of current natural gas consists of helium. So, it's not all that rare which helps to explain why it's not all that expensive.