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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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Low Earth Orbit.
Yea, good and explosive. While it may not be particularly dangerous to people, losing payloads to accidents involving hydrogen explosions in the atmosphere would jack the potential cost up.
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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?
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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.
People have a misconception that if you put a hole in a blimp, that it crashes. If properly designed it will not.
It all comes down to the pressure difference between the insides and the outsides of the blimp.
Reading their promotional literature, they do not maintain much of a pressure difference between the insides of the blimp and the outsides. Thus, a hole will not really result in the helium being replaced with the heavier atmospheric gases.
Most blimps can manage a safe emergency landing if even significantly damaged.
Last but not least, I suspect that their choice of helium was more due to the dramatic reduction in safety precautions they have to take with the stuff on the ground. There are real advantages to using diatomic gases over monotomic gases (for example, they leak much more slowly through micro-pores). But the advantages do not make up for the disadvantage of the risk of explosion on the ground or at low altitudes.
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.
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http://www.jpaerospace.com/atohandout.pdf
Here are the details:
Atmospheric airship with crew of three takes payload to 140,000 ft. Airship uses lift and buoyancy, and driven by propellers designed to operate in near vacuum.
Dark Sky Station (DSS) at 140,000 ft. Permanent, crewed facility.
Airship that flies from DSS to orbit. Over a mile long. Uses buoyancy to climb to 200,000 ft. From there uses solar/electric propulsion to reach orbital velocity over several days.
Continuing to use solar/electic propulsion, it can keep on going to anywhere in the solar system.
Several "DSS" platforms have been flown. All equipment has been flown at 100,000 ft. and tested in the environment. Ion engine tests of the orbital airship at 120,000 ft. will occur in the next five months.
Every segment of the plan has funding. DoD is funding the atmospheric airship for reconnaissance. Telecom companies are funding DSS.
Yes. Atomic oxygen (O1), standard diatomic oxygen (O2, the kind we breathe), and ozone (O3, the kind the blocks UV and gets eaten by fluorocarbons). O1 and O3 are very reactive, but nothing that a hydrogen balloon should have to worry about, so long as it contains most of its hydrogen.
Of course, one of the other great benefits of helium over hydrogen is that helium is MUCH more containable - He stays inside Mylar envelopes a lot longer than H, which has been known to burrow its way out of multi-layer metal/ceramic containers thanks to its small atomic size.
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Actually it is. Any Nuclear reactor can be tuned to produce Helium. I think they did this briefly at the Laurence Livermoor reactor for a short time before decomissioning it.
"Curiosity killed the cat, but for a while I was a suspect."- Steven Wright
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'.
This blimp needs air for bouyant lift, so you are inevitably going to be in the atmosphere. Ion engines, unfortunately, only work in a vacuum. And even if they did work at that altitude, the drag would so high that they wouldn't accelerate the ship at all.
.01, then the drag force at 5000 fps, 1/5 of orbital velocity, is: .5 rho Cd V^2 A
.01
If the ship was, say, 50 ft wide and had a rediculously low drag coefficient of
where
rho is density (about 1.7x10^-5 slugs/ft^3)
Cd is
V^2 is velocity squared. At 5000 fps, that's 2.5x10^7
A is area, 50 ft
This yeilds a drag of a little more than 100 lbf.
The most powerful ion engine is Nasa's new HiPEP that has a thrust of about 1/10th of a pound.
Now, I'm a big fan of JP Aerospace, and wish them all the luck in the world. Their program of launching sounding rockets from high-altitude balloon platforms was quite exciting. Hypersonic blimps, though, are just not going to happen.
Thad
I love Mondays. On a Monday, anything is possible.
Yes, I know you won't get aerodynamic lift without air, so there will be some drag, but your back-of-envelope calculation doesn't tell enough of the story to know if it's a showstopper.
My question is how the heat gets dumped on the way back. I guess it has so much surface are the heat load at any given point is small, but we're not talking about titanium here.
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.