Man falls from space

[Bob in a quantum-state-of-faith]

... and breaks the sound barrier on the way down, lands safely via parachute

http://www.youtube.com/watch?feature=player_embedded&v=FHtvDA0W34I

[youtube=425,350]FHtvDA0W34I[/youtube]

After flying to an altitude of 39,045 meters (128,100 feet) in a helium-filled balloon, Felix Baumgartner completed a record breaking jump for the ages from the edge of space, exactly 65 years after Chuck Yeager first broke the sound barrier flying in an experimental rocket-powered airplane. Felix reached a maximum of speed of 1,342.8 km/h (833mph) through the near vacuum of the stratosphere before being slowed by the atmosphere later during his 4:20 minute long freefall. The 43-year-old Austrian skydiving expert also broke two other world records (highest freefall, highest manned balloon flight), leaving the one for the longest freefall to project mentor Col. Joe Kittinger.

Watch the Full Recap: http://www.youtube.com/watch?v=dOoHArAzdug

(emphasis mine... it's cool... watch the long video if you can, it's only 5 minutes)

[Griffin NoName]

Paul Merton suggested bungee jumping might have been fun in this context

[Sibling DavidH]

I can't get over the fact that a balloon will take a load up to 10mB.  Yes, I know it's Archimedes thingy, but it still seems counter-intuitive.

And I wonder why they didn't use hydrogen for an odd one like this.  The Helium cost a fortune.  I know about the safety aspect and the Hindenburg and all that, but surely for this event you could accept that tiny risk.  You could make your balloon a lot smaller, too.

[Swatopluk]

Half the size actually but hydrogen has the other disadvantage that it is far more able to escape.
What surprises me that the whole thing holds together with a hull only 20 µm thin (even with stabilizer bands).

[Swatopluk]

Btw, what happened to capsule and baloon?

[Griffin NoName]

They continued upwards until they hit Andromina, split into three chunks and fell back to earth, knocking Mrs Jane Tripset off her bike.




No idea

[pieces o nine]

...comment on this event at TOP, thought you dujes would enjoy it...   

[Sibling DavidH]

They continued upwards until they hit Andromina, split into three chunks and fell back to earth, knocking Mrs Jane Tripset off her bike.No idea

LOL

[Bob in a quantum-state-of-faith]

Btw, what happened to capsule and baloon?

I asked that very same question myself-- could not find a straight answer.   It was clear there was a mechanism in place to abort the mission from the outside, and with the medical monitoring equipment onboard, I presume a way to abort via radio command.  So one would presume the capsule also had a parachute of some kind.

So, initiate that command, to release the balloon, and let the capsule fall and remotely open the chute?  Or was there a pressure-activated switch on-board?  (another obvious engineering safety)

The balloon itself would rise high enough to explode--it's what they typically do with ultra-high altitude weather balloons after all.  The fabric would drift a bit, but eventually end up in the ocean, where sunlight slowly breaks it down--or so I'm told.  

________________________

Follow up article:  How close to space was he?

http://io9.com/5952443/infographic-reveals-just-how-far-felix-baumgartner-really-was-from-space

Short answer:  not that much, actually...

The linked article published a lovely graph that puts things in proportion:



So, from this, it was clear he was about 1/3 or so the way to the lowest stable earth-orbit.

Which is still quite an achievement for someone only wearing a space suit.

[Bob in a quantum-state-of-faith]

What happened to the capsule?

Yaaay to UK reporters for addressing this question:

http://www.guardian.co.uk/sport/shortcuts/2012/oct/15/felix-baumgartner-skydive-key-questions-answered

As soon as it was confirmed that Baumgartner had landed safely, the attention of mission control shifted to the balloon and capsule. The team remotely detached the capsule from the balloon, allowing it to fall back to Earth under its own parachute. It hit the ground 55 miles east of Baumgartner's own landing site. The balloon was deflated via a nylon "destruct line", with the lightweight balloon material – known as the envelope – falling back to Earth to be gathered and removed by truck. The capsule could, in theory, be used again, but the balloon envelope can only be used once.

Well, I was right in that they had both a remote-release switch, and a dedicated parachute for the capsule itself.  But I got the balloon question totally wrong.  I'm gratified they didn't let it drift into the ocean.

Read the link-- it answers quite a few questions about the technology of the jump.

[Sibling DavidH]

Half the size actually but hydrogen has the other disadvantage that it is far more able to escape.

OK, but if it will stay in a doped cotton bag long enough to get an airship across the Atlantic, it'll stay in a bag made of a modern material for two hours.

[Swatopluk]

It's a bit more complicated than that. But I think safety is not the only reason.
I'd have to check though, whether under the flight conditions the fire hazard plays any significant role. Accidents tend to happen close to the ground usually.
Also in a zeppelin there is enclosed space between gas cells and outer atmosphere where the really dangerous mixes can form. Under this aspect a balloon is actually safer.

[Bob in a quantum-state-of-faith]

Half the size actually but hydrogen has the other disadvantage that it is far more able to escape.

OK, but if it will stay in a doped cotton bag long enough to get an airship across the Atlantic, it'll stay in a bag made of a modern material for two hours.

There's the Big Danger myth to overcome too.  /end sarcasm

If anything went wrong-- anything at all-- even the tiniest thing-- the media would blame it on that H2, even if it had nothing to do with anything.

So, they'd be without any sort of insurance.

And?  Many of the health professionals who might otherwise volunteer to be on-hand just for the recognition-rights, would stay away just because of the perceived danger.

Then, again, there's media hype: 

"Oh Noes!  Woe!  They are using dangermous.... hydrogenses!   Oh worra-worra--run-and-shout-scream-and-wail!  Oh Noes!"

Helium is not that much more expensive-- most of the stuff we use in the USA comes from natural gas wells-- "fossil helium" as it were.  And it simply side-steps all the ... artificial hysterical nonsense.

[Swatopluk]

Few people know that many or even most of the deaths of the Hindenburg desaster had little to do with the fire. Many people jumped out of the airship before it touched ground or the flames even came close to them. Those passengers that kept their nerves and waited for the most part survived. And the really nasty parts of the fire where from the fuel oil of the engines not the hydrogen.

[Sibling DavidH]

Now here's another question:  the organisers claimed that this will help prove that  astronauts stranded in orbit can get back down without a capsule.  Hmm ... don't they think it might get a bit warm on re-entry?

[Bob in a quantum-state-of-faith]

Now here's another question:  the organisers claimed that this will help prove that  astronauts stranded in orbit can get back down without a capsule.  Hmm ... don't they think it might get a bit warm on re-entry?

Some actually talked about that very issue, on some of the other news articles I read (when searching for "what happened to the capsule").

They pointed out that this was a very early first step towards orbital re-entry in a space suit (aka Robert Heinlein's Starship Troopers). 

Coming down from orbit has two factors: 

1) your relative surface-speed is incredibly high-- that is, you are moving with respect to the surface, many times the speed of sound (you must, to remain in orbit).
2) using the atmosphere as an air-brake involves some pretty high temperatures that would have to be addressed.

Now, if the potential re-entry was fixed relative to the surface, as was the case with this jump, then the suit he used could easily be used here--provided it had enough air to last until the traveler was low enough.  Simple gravity would bring the jumper down, and the gradual thickening of the atmosphere would serve for gentle braking-- as was exactly the case here.   The stickler would be if they jumper was too high, and could possibly generate too much speed before entering the thicker, lower atmosphere-- of course, some sort of small pre-chute could easily be employed to slow the reentry with sufficient gentleness.

I see two possible ways to land from a low earth orbit, in a suit:

1) some sort of solid rocket booster, which would kill your orbital speed down to one that was manageable with drag chutes before you re-enter the atmosphere
--or--
2) some sort of ablative heat shield compound in an outer casing (as what Heinlein envisioned with his Drop Troopers).

Likely a combination of each-- rockets to slow your orbital speed to something not-orbital, allowing gravity to do it's thing and an outer casing that would melt away (taking heat with it) to slow you even more.

This experiment/stunt ignored all of that, and concentrated in the last stage of the re-entry process:  keeping someone alive in near-vacuum and ultra-low temperatures.

[Sibling Zono (anon1mat0)]

Vertical vs Horizontal.

If you are falling in a vertical pattern you spend less time on the atmosphere, but while in orbit the approach vector is closer to horizontal and at a high speed, increasing the amount of friction and therefore heat. If you change the vector (ie, lower your orbital velocity) friction should be lower.

_{(this is me in high conjecture/out of my @$$ mode )}

[Bob in a quantum-state-of-faith]

Vertical vs Horizontal.

If you are falling in a vertical pattern you spend less time on the atmosphere, but while in orbit the approach vector is closer to horizontal and at a high speed, increasing the amount of friction and therefore heat. If you change the vector (ie, lower your orbital velocity) friction should be lower.

_{(this is me in high conjecture/out of my @$$ mode )}

Velocity has a great deal to do with either approach.  Meteors hit the atmosphere at all sorts of angles, including near-vertical-- but their relative speed (with respect to the atmosphere) is very high, so they typically burn up.

Orbital velocity with respect to the ground is quite high-- many, many times the speed of sound.   But it's a balancing thing, the velocity has to be just so, or you'll change orbits, as gravity is a fixed thing (well, apart from it's inverse-square-with-distance thing, it's fixed).

Change [reduce]* your orbital velocity enough, and you literally fall out of orbit-- but, you're still going many-many times the speed of sound.   It'd take a freakin' huge booster engine to kill that velocity enough, that you'd be falling at ordinary speeds (i.e. a speed just due to acceleration of gravity for example).   Any mass put into orbit cost lots of boost-energy to get it up there:  so, instead of a giant retro-rocket thing, engineers use the atmosphere instead [for braking].

Now, imagine a Star-Trek teleporting machine, one that preserves angular momentum (i.e. the speed of the earth's surface rotating with respect to it's whole mass).   Use the machine to teleport yourself directly up-wards into the blackness of actual space.  Then, you begin to fall (after a cartoonish pause to permit you to get your bearings, and realize you're really, really high up... naturally... ) accelerating due to the effects of gravity, but also traveling horizontally with respect to the whole earth's mass-- roughly the same speed as the surface.

But, the atmosphere is (more or less) also moving at the same speed, in roughly the same direction... mostly due to friction I'm told.

So in this hypothetical case, your only speed with respect to the atmosphere is due to gravity:  how high can you go, before you have enough time to accelerate to dangerous velocities before re-entering the atmosphere?



In truth, I do not know the answer.  Earth's gravitational pull is 32 feet per second per second, and is always "on".   According to the chart above, there's enough atmosphere at 280,000 feet to burn up meteors that are going too fast.

So I would surmise you'd likely not wish to start a whole lot higher than that figure--else you'd get sufficient velocity that once you did get to 280,000 feet, you'd burn up too.

Keeping in mind that "terminal velocity" only works inside of an atmosphere... such that your acceleration due to gravity theoretically has no upper limit--and given sufficient distance under constant gravity, you could theoretically exceed even light-speed.

Obviously, the earth's gravitational well is insufficiently deep for such a stunt.  But suppose you had you a massive black hole... one the size of a galaxy, say... hmmm.


_____________

* if you increase your orbital velocity, you move to a higher orbit-- increase it enough, you fall out of orbit into space.

[Swatopluk]

Of course there is also the difference between circular and elliptical orbits (the former is one extreme of the latter). Circular orbits are elementary, elliptical ones require a good deal more math. The lowest and slowest orbit would be a circular one at ground level with about 8 km/s (5 miles per second) constant orbital speed. In an elliptical orbit speed depends on the position. At least one space probe used long ellipses for a very energy effficient braking maneuvre where it would go twice per round through the high atmosphere losing only tangential speed, so the ellipsis grew shorter each time but without losing height until the oribit had become almost circular. It took ages but consumed very little fuel.
A 'cold' orbital entry would be possible but tricky by a combination of drag (reducing speed relative to the atmosphere) and lift (reducing the speed of descent). Both would have to be adjusted over time with probably not much freedom of variation. Not something one could put into a suit, I presume.

[Sibling Zono (anon1mat0)]

One case in point, imagine we have the space elevator up to the geosynchronous orbit, and a quarter of the trip you jump from it. Drag should be a function of atmospheric density at any height, and the question is at what point terminal velocity would make you burn in the atmosphere. That same principle applies to parachutes in Mars.

[Bob in a quantum-state-of-faith]

High enough, and you'd have to worry where the moon was at-- for there's an equilibrium point betwixt the moon and the earth- but that's most of the way to the moon, so no real worry here.

As for a space elevator up to geosynchronous orbit?  That'd be high enough, I would wager, that you'd reach dangerous velocities before the atmosphere was dense enough to be effective on a normal human-sized falling body.

Of course, orbital dynamics tells us that the hypothetical elevator needn't be quite that high-- anything above the atmosphere, and centripetal forces hold it up (the force that holds water into a bucket as you swing it on a rope around your head, misnamed "centrifugal force").

In fact, once you reach a certain altitude, those forces push you up to the elevator's terminus-- the rotational effect of that elevator being fixed to the earth at one point. Obviously, a person leaping from such a point would go into orbit, instead of falling.  And now, I don't know how high that would be.  Arther C Clarke explains it all in his novel, The Fountains of Paradise and also in the novel 2061.   But, to figure it out, you'd take the rotational speed of the earth, and compute how high an orbit that would be... hmmm... geosynchronous?  So maybe I'm all wet at presuming a lower elevator .. it's been awhile since I studied this stuff, actually.

[Swatopluk]

There is also a very readable paper (or two) in the Acta Astronautica. Don't know whether it is availabe online for free. It goes into great detail about how to actually build the thing, how far it has to extend etc.
To simplify it a bit: One line gets dropped from a satellite then a robot crawls up it drawing the next strand behind it. the next one crawls behind with two more and so forth. The robots can be used as the counterweights at the upper end, allowing for a shorter toital length of line. This way reduces the failure risk significantly and also the costs, should it happen anyway. Using multiple lines (actually bands) makes the whole thing also less sensitive to damage and easier to repair.

[Bob in a quantum-state-of-faith]

Clarke surmised using carbon in the form of stranded diamond fiber in 2061.  (His novel was written prior to the discovery of nano-carbon tubes.)