Supersonic Jump, From 23 Miles Up

Although not strictly 'Aviation', I thought this would be of interest on this forum, and the discussion might be more thoughtful than in P&R...... Experienced jumpers and ex-military types (Taz?) may have some interesting viewpoints, especially on the issues of the body going trans- then supersonic......comments?

A Supersonic Jump, From 23 Miles in the Air

Ordinarily, Felix Baumgartner would not need a lot of practice in the science of falling.
He has jumped off two of the tallest buildings in the world, as well as the statue of Christ in Rio de Janeiro (a 95-foot leap for which he claimed a low-altitude record for parachuting). He has sky-dived across the English Channel. He once plunged into the black void of a 623-foot-deep cave, which he formerly considered the most difficult jump of his career.

But now Fearless Felix, as his fans call him, has something more difficult on the agenda: jumping from a helium balloon in the stratosphere at least 120,000 feet above Earth. Within about half a minute, he figures, he would be going 690 miles per hour and become the first skydiver to break the speed of sound. After a free fall lasting five and a half minutes, his parachute would open and land him about 23 miles below the balloon.

At least, that’s the plan, although no one really knows what the shock wave will do to his body as it exceeds the speed of sound. The jump, expected sometime this year, would break one of the most venerable aerospace records. For half a century, no one has surpassed (one person died trying) the altitude record set by Joe Kittinger as part of an Air Force program called Project Excelsior.

In 1960, Mr. Kittinger, then a 32-year-old Air Force pilot, jumped from a balloon 102,800 feet above the New Mexico desert. Today, at 81, Mr. Kittinger is a retired colonel and part of the Red Bull Stratos team working on Mr. Baumgartner’s jump, which is being financed by the energy-drink company.

“For 50 years,” Mr. Kittinger said, “I’ve gotten phone calls from all over the world, people wanting to break my record — one a month, sometimes two a month. But I stayed away from them because they didn’t have any idea what the challenge was. What attracted me to Red Bull was their methodological approach to safety and to providing scientific benefits.”

More than three dozen veterans of NASA, the Air Force and the aerospace industry have been working for three years to plan the jump, build a balloon and pressurized capsule, and customize an astronaut’s suit for Mr. Baumgartner. Besides aiming at records, they’re doing physiological research and developing procedures for future astronauts to survive a loss of cabin pressure or an emergency bailout in the stratosphere.

One of the chief concerns has been to avoid the problem that almost killed Mr. Kittinger during Project Excelsior. He was supposed to be stabilized during his fall by a small drogue parachute, but on one training jump in 1959 it did not open because the cord got tangled around his neck.

As a result, Mr. Kittinger’s body went into a spin that reached 120 revolutions per minute as he plummeted more than 60,000 feet. He blacked out and regained consciousness only after his reserve parachute opened automatically about a mile above the ground. When he came to, he later wrote, he first assumed he must have died, but then he spotted the parachute’s canopy above him and made a sudden realization: “I am impossibly, wonderfully alive.”

Mr. Baumgartner hopes to remain stable and conscious throughout his longer fall without relying on a drogue parachute. He plans to avoid spinning by adjusting the angle of his body and keeping his arms at his side.

This stabilizing technique would ordinarily be fairly easy for an expert like Mr. Baumgartner, 41, a former paratrooper in the Austrian Special Forces and a veteran of more than 2,500 jumps from planes, cliffs and assorted landmarks. But to survive the stratosphere’s near vacuum and frigid temperatures, he will need a sealed helmet and a pressurized suit.

Would he be able to do midair maneuvers in such a bulky contraption? To find out, Mr. Baumgartner and his team recently went to a wind tunnel in Perris, Calif., near Los Angeles, and put the suit through its paces.

Team members suited up Mr. Baumgartner, turned on the oxygen in his helmet and attached a pack to his chest containing equipment to record his vital signs, track his position using GPS satellites and heat his helmet’s visor to keep it from fogging.

By the time the suit was inflated to its full pressure of three pounds per square inch, he looked like a robotic version of the Incredible Hulk. As he walked stiffly into the wind tunnel, it was easy to see why astronauts lack a certain grace.

But once Mr. Baumgartner was inside, held aloft by air blowing upward at 130 miles per hour, he looked comfortable enough, much to the relief of the engineers. By adjusting his arms and legs, he could shoot up in the tunnel or bring himself down. Most important, with his body angled at 45 degrees to the ground, he could maintain the desired arrowlike stance: head first, arms and legs pointing backward in a V shape called the delta position.

“It was difficult, but it worked,” Mr. Baumgartner said after emerging from the tunnel. “Now I’m confident I can handle the suit in regular free fall as long as we’re not breaking the speed of sound. But as soon as it goes from subsonic to transonic to supersonic, we don’t know what to expect.”

Plenty of planes have broken the sound barrier, but transonic humans are a mystery, said Art Thompson, the technical project director for the Red Bull Stratos mission, and a former Northrop engineer who worked on the B-2 stealth bomber.

“You can run a lot of models, but with the human body you’re not dealing with a hard surface or a ballistic shape,” Mr. Thompson said. “You’ve got this rounded bulbous helmet, and the shoulders and the feet sticking out, and everything starts to happen at different times. Parts of your body may be going supersonic while others aren’t, causing flutter waves pulling back and forth among the surfaces.”

Could such waves harm the body? Could they create disastrous turbulence?

“We just don’t know what will happen to Felix and the suit when he goes supersonic,” said another Stratos engineer, Mike Todd, who worked on high-altitude suits for the Air Force’s spy-plane pilots with the renowned Skunk Works research division of Lockheed. “Felix could slip right through it, but if half the suit’s supersonic and the other half isn’t, there could be turbulence that knocks him out of control.”

Such risks are one reason why Mr. Kittinger’s record has stood for half a century. Air Force and NASA officials have become understandably reluctant to explain potential mishaps to Congressional committees. (To debate the risks and benefits of this project, go to nytimes.com/tierneylab.)

But private adventurers have more freedom to take their own risks. The Stratos medical director, Dr. Jonathan Clark, who formerly oversaw the health of space shuttle crews at NASA, says that the spirit of this project reminds him of stories from the first days of the space age.

“This is really risky stuff, putting someone up there in that extreme environment and breaking the sound barrier,” Dr. Clark said. “It’s going to be a major technical feat. It’s like early NASA, this heady feeling that we don’t know what we’re up against but we’re going to do everything we can to overcome it.”

JOHN TIERNEY
March 15, 2010

 

I'm curious what temperatures friction will produce at that speed. Seems like it could affect the suit's integrity. But, what do I know?

CW

 

He'll be fine if the drogue works correctly.

There are many documented instances of aircrew ejecting, and being involuntarily ejected from the SR-71 at speeds as high as mach 3+. Their pressure suits inflated and acted as a capsule protecting them from the supersonic blast and other forces.

 

I wonder if his ears will "pop".

 

Really? I mean that makes sense, but I've been over Mach 1, and the heat alone was enough to make it uncomfortable. And, the normal forces of expansion and contraction at that temperature would seem to be problematic. But, you've got to be right about this.

CW

 

Doesn't look like one will be involved:

 

The SR-71 had a capsule system for each crew member to protect the crew during ejection. No way a pressure suit would have protected someone from the high q (airload) environment of a mach three ejection. Would have ripped off the arms and legs.

The high altitude paradrop should be technically feasible. During the supersonic portion of the drop, both air loads and heating will be relatively low since air density is so low at high altitude. As he falls into denser atmosphere, terminal velocity, which was supersonic at very high altitude, will drop on a logarithmic scale so that neither airloads nor heating will be a problem.

The big problems he faces are the time of fall and low temperatures at high altitude. As long as he has sufficient oxygen to make it to 25Kft or so, he should have no problems there. I assume his suit will be heated for the drop. It is really cold up there.

Taz
Terry Phillips

 

I doubt this will be an issue.

Atmospheric pressure increases with atmospheric density and reaches 14.7 at sea level. By contrast, scuba divers increase an atmosphere every 33 feet/10 meters in sea water. This will be no more of an ear problem for him than a diver going less than 33 feet.

 

Affirmative- Not much pressure change for most of the drop and the pressure suit will act like an airliner pressurization system. Valsalva will undoubtedly be required after the pressure suit is depressurized at lower altitude, but not a big deal. Change in pressure increases with decreasing altitude, again on a logarithmic scale. Worst that can happen is two busted ear drums, which will heal fairly quickly.

The jumper in question has already done dozens of HALO jumps, so it will not be a problem for him. He has already seen all the worst of the pressure changes, and knows how to cope with them.

Taz
Terry Phillips

 

What about attitude control vis a vis turbulence during his speed changes from subsonic to transonic to supersonic and back transonic to subsonic? Seems like a big risk of getting out of shape and spinning/tumbling? that could hurt......any control measures beyond luck?

 

Sounds like a drogue chute is needed here but what do I know about supersonic free fall flight. Absolutely nothing.
Switches

 

Turbulence is caused by atmosphere. At high altitude there is less atmosphere. Also, the speed of sound is relative to atmospheric density.

He will be freefalling at very high speeds but the sensation will be less than freefalling from ten thousand due to lack of atmosphere density. As he approaches the planet surface, the atmospheric density will increase and slow his descent. So the farther he falls, the slower he goes.

[edit] ...
Keep in mind that when they do EVA's on the ISS it looks like they're floating in space but they're actually frefalling toward earth at over 17k MPH. Since there is no atmosphere in space there is no turbulence.

 

The B-58 Hustler had an enclosed capsule seat system........the SR-71's did not.......and I didn't understand why until this morning.

Here's info on the SR-71 seat system.

http://www.ejectionsite.com/sr1seat.htm

This is an interesting factoid I didn't know about, from that link........it explains why they would be OK with just pressure suits. And why the B-58 crew......whizzing along Mach 1 or 2 at, or below 60,000' would not be, ergo their need for the capsule.......

"The SR-71 flying at 2000mph at near 80,000 feet is actually experiencing wind force more equivalent to about 460 MPH (400 Knots Equivalent Air Speed {KEAS}). Aircraft such as the FB-111 were designed for speeds down in the thicker atmosphere, and thus experience a much higher 'Q' or dynamic pressure."

There are documented cases of ejections at high mach and altitude and in fact I read one yesterday. Here's the link to it from the pilot's own account......

http://www.alexisparkinn.com/sr-71_break-up.htm

Mach 3.2 at 78,000'..........

"Everything seemed to unfold in slow motion. I learned later the time
from event onset to catastrophic departure from controlled flight was
only 2-3 sec. Still trying to communicate with Jim, I blacked out,
succumbing to extremely high g-forces. The SR-71 then literally
disintegrated around us.

"AS FULL AWARENESS took hold, I realized I was not dead, but had
somehow separated from the airplane. I had no idea how this could
have happened; I hadn't initiated an ejection.

The pressure suit was inflated, so I knew an emergency oxygen
cylinder in the seat kit attached to my parachute harness was
functioning. It not only supplied breathing oxygen, but also
pressurized the suit, preventing my blood from boiling at extremely
high altitudes. I didn't appreciate it at the time, but the suit's
pressurization had also provided physical protection from intense
buffeting and g-forces. That inflated suit had become my own escape
capsule.

My next concern was about stability and tumbling. Air density at high
altitude is insufficient to resist a body's tumbling motions, and
centrifugal forces high enough to cause physical injury could develop
quickly. For that reason, the SR-71's parachute system was designed
to automatically deploy a small-diameter stabilizing chute shortly
after ejection and seat separation. Since I had not intentionally
activated the ejection system--and assuming all automatic functions
depended on a proper ejection sequence--it occurred to me the
stabilizing chute may not have deployed."

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There was a guy from France who was supposed to try to do this jump a few months ago in the province of Saskatchewan but couldn't do so due to technical issues.

 

KDS- You are correct. I misread a quote from one of the successful ejections where the crewmember mentioned feeling safe in his capsule. He was referring to his pressure suit. SR-71 ejections are closely related to the high altitude parachute drop someone is attempting, where q (airloads) is low due to the thin air at high altitudes.

Some U-2s had a dual range airspeed indicator for the same reason. At service ceiling, the indicated or calibrated airspeed difference between stall and the aircraft breaking up is very small. Too small to read on a normal airspeed indicator.

Taz
Terry Phillips

 

I didn't know this and was just reading about it yesterday from something totally unrelated to this thread. Interesting about atmospheric differences at altitude and their affects as related to forward speed. I never would have figured it that way at all.