>The subject’s last memory before passing out was the realization that the water on his tongue was boiling, according to NASA.
That is not something I would ever want to experience.
I wonder how similar this environment is the the SR71 that disintegrated [1]. Luckily the SR71 pilots wore space suits with this happened. Otherwise I dont think he would have survived.
In addition to the boiling spit thing, he was rammed at Mach 1 into -57C air at 15km altitude, without wearing some fancy astronaut suit, coming out of a space vehicle disintegrating around him. Then he regained consciousness en route down to Earth and unbuckled the seat. How was the whole ordeal survivable - I can't even begin to imagine.
Yeager famously survived an accident with a modified F-104 that was in some ways quite similar to the SpaceX craft (i.e. a plane with a rocket that can fly an arc up out of the atmosphere). Quite a few of these rocket-plane flights were considered spaceflight at the time, though they don't meet the modern (100km) definition.
But pop rocks at 15km when you've just been blown out of a malfunctioning space vehicle still strapped to your chair while you're tryi to unbuckle it so you can pull the shute.
The context is an account of an incident in a NASA vacuum testing chamber where a tester's suit lost pressure, not of the crash.
I'm quite certain both experiences on the whole would be terrifying, but as the detail of the saliva boiling on the tongue was singled out to be terrifying on its own, that is what I based my comment on.
In my imagining of what it would feel like to have your saliva boil yet not be under a great amount of heat, I can only imagine it would feel like a mouth full of pop rocks. I don't find that terrifying.
According to the pilot, he was unaware that the feather system had been unlocked early by the copilot. His description of the vehicle motion was consistent with other data sources in the investigation. He stated that he was extracted from the vehicle as a result of the break-up sequence and unbuckled from his seat at some point before the parachute deployed automatically.
Recorded information from telemetry, non-volatile memory, and videos are being processed and validated to assist the investigative groups.
... The investigation is ongoing. Any future updates will be issued as events warrant.
I was also interested in the fast that they weren't in pressure suits. Apparently the ingress/egress hatch is so small as to preclude them wearing basic safety equipment. I'm becoming less and less sympathetic to Virgin Galactic the more I hear.
Cut the company some slack. Space flight is hard. There are physical constraints imposed by the laws of Nature that have to be carefully weighed. It is easy to forget this fact when all you ever do is software design or whatever.
Not too much slack. It's true that space flight is hard. But it's also true that Virgin Galactic is a company based entirely around sub-orbital space tourism. The level of risk we should consider acceptable for what's essentially an ultra-high-priced amusement park ride is rather lower than the level of risk we should consider acceptable for space exploration.
People who pay to go can make their own decision if the risk is acceptable to them or not. It's not anyone else's business to decide what the acceptable level of risk is.
>People who pay to go can make their own decision if the risk is acceptable to them or not. It's not anyone else's business to decide what the acceptable level of risk is.
until they are a MIT trained airspace engineers, i doubt they are able to estimate the risk and thus to make a fully informed decision on their own. This is why it is official government agencies' business to at least establish minimum acceptable risk baselines.
And that's how you end up in a society where all risk-taking is banned to the fringes. No thanks, I'd much rather sign the "waiver from hell". High-risk activities CAN be self-regulated by industry, i.e. skydiving.
I'm no expert on this subject, but a small amount of Googling suggests that rumors of skydiving's lack of regulation in the US have been greatly exaggerated. For example, you can't just pack your own chute - there's a special FAA certification you have to get before you're allowed to do that.
The rules I'm seeing seem more like the ones that govern recreational sailing, which is a topic I'm more familiar with: If you're just doing it on your own, sailing is fairly lightly regulated. Your boat needs to meet some minimum requirements for safety equipment and the like, but for the most part all the rules for recreational sailing are voluntary and self-imposed by the community.
But all that goes out the window once you start doing it commercially. If you want to take tourists out on a day sail, you need to be a licensed captain and there's a whole host of federally-imposed rules about how you operate your boat that come into play.
Virgin Galactic isn't analogous to some guy day-sailing in his own boat. SpaceShipOne would have been, but SpaceShipTwo is much more analogous to commercial sailing, which is comprehensively regulated for the sake of consumer protection.
I wouldn't say this parallels with skydiving as it's something new. If I choose to go skydiving I can easily get a grasp on how dangerous it is by looking up statistics and choosing a reputable company with a good track record. If I choose to take a Virgin Galactic trip then unless I possess very specialist knowledge I just have to take their word that it's "safe".
this is why lessons of previous attempts in the industry should be rolled into the next ones. Pressure suits on launch is standard long established practice in space flight industry since the dawn of times, and so far there is no evidence that it should be changed.
There's slack, and then there's there's unnecessary risk. If you can't fit a basic piece of safety equipment on your test pilot then you need to rethink your strategy.
I couldn't find any information on who manufactured the automatic activation device, but it was almost certainly not an off the shelf model. Airtec created a specialized Cypres[1] for the Redbull Stratos project, and Cypres has had other applications in space, so I wouldn't be surprised if that's what was used.
AADs have barometric sensors. That works for skydivers because they zero it on the ground, they're in an unpressurized vessel and they always experience the same force vectors (with variations, belly vs. freefly &c).
How would you build a CYPRES-style (barometric, integrated, cutter based) AAD for an event like this? And why would you not have it built into the seat?
Speculation: they wore standard bail outs sans AAD, like regular pilots. This guy either don't remember pulling or had the forces excerted on him and/or his gear pull for him.
CYPRES AADs work based on calculating rate of decent, not from some triggered barometric pressure. With modern micro-controllers it's practically trivial to tell the difference between a barometric altimeter sensor history of pressure changes in a cabin and pressure changes due to free falling through the open atmosphere. From there it's just a matter of triggering based on rate of decent, altitude ranges, etc.
Note how they call out that you can keep it activated on the ground, in vehicles, in pressurized cabins, etc. without fear of accidental automatic activation.
Rate of descent is calculated from barometric pressure in a CYPRES.
When a CYPRES is turned on, it calibrates itself and uses the current barometric pressure to determine the reference ground. When you enter an unpressurized aircraft and begi your ascent, the CYPRES will arm itself above a certain altitude (1000 ft normally). When you exit the aircraft, the CYPRES knows your altitude because of the difference in barometric pressure between the reference ground and the urrent pressure. It will also calculate your rate of descent from change in barometric pressure over time. It will activate if you're too low and too fast.
Notice how the environment is fairly static. You're jumping right above your reference. You're in an unpressurized vessel so the CYPRES can tell when to arm itself. You're starting a descent by exiting a level-flying aircraft. Any departure from normal operating limits and the CYPRES will not arm itself or activate at the proper speed and altitude.
You want a system like fighter pilots have and not something skydivers use. The environments are different, the operational requirements are different.
After all the speculation about engine failure, it sounds like the culprit is a combination of poor design and pilot error.
The "Feather System" was unlocked by a pilot too early in the flight, then air currents caused it to activate in atmosphere instead of near vacuum - likely tearing the ship apart.
10-11 years ago I followed the Ansari X Prize a lot. I have a fuzzy recollection that Peter Siebold, the surviving pilot, actually designed and, at least in part, programmed almost everything related to pilot controls (and lots lots more!) on the SpaceShipOne.
If pilot controls are similar on SpaceShipTwo and poor design of them is blamed in the final NTSB report, then I hope Peter doesn't put too much blame on himself.
Peter Siebold has given and achieved so much on this project, definitely a hero of mine together with Burt Rutan.
But part of the flight procedure is to actually unlock the feathers slightly later in the flight - at Mach 1.4.
The article states this is to make sure the feathers are operational before heading upward, but that seems like a really narrow margin of time to execute this test.
While speed is a factor, it isn't the only factor. The altitude at which they are unlocked matters as well. Moving at Mach 1.0 at a lower altitude could subject the plane to far greater forces than at Mach 1.4 at a much higher altitude, where the air is thinner.
Furthermore, where the force is coming from probably also plays a role. The angle of the force applied to the feathers may change when the force is not coming from a fall, but is instead the result of the engines provide force from behind the fuselage.
Not poor design, the Feather System has to be unlocked at some point. And testing it early, at Mach 1.4 might be a really good idea before you (I assume) commit to needing it.
And there's a good possibility removing its contribution to the center of pressure too early is what caused the destruction.
Hard to say if poor design is a contributing factor or not - if the release mechanism is easily confused because it's a tiny little switch that looks just like all the other tiny little switches, then yeah, it may be poor design. In new endeavors, especially the often unforgiving aviation arena, frequent and focused training often makes up for poor design, or less-than-wonderful human factors engineering, or other recognized-after-the-event shortcomings - until it doesn't.
I would assume that in typical aircraft cockpit, most of the prominently placed tiny little switches are actually important and unimportant tiny little switches are the exception.
Apparently yes. He was found in the wreckage, strapped in his seat, with the chute partially deployed. It probably deployed automatically during the fall and shot out between the pilot and the seat.
If you don't have an ejection seat, getting kicked out of your seat inside a cockpit doesn't sound terribly helpful. Inflight breakup situations where the pilot breaks free in their seat are so rare that this would probably would cause more accidents than it would save lives.
Ejection seats do kick you out of the seat automatically sometime after ejection so that the automatic parachute deployment can work.
Inflight breakup situations where the pilot breaks free in their seat are so rare...
Do intuitions developed about airframe integrity in an aviation context necessarily apply to spaceflight? Normally I wouldn't think automatic chute deployment would have much value without a full ejection seat, although in this case it saved a life. Did the designers of this craft actually have a meeting in which they decided that the likelihood of this exact sort of incident is so much higher than an intact-vehicle incident that an automatic chute is warranted while an ejection seat is not?
For some reason I suspect that a couple of years from now we'll be reading a tell-all about the culture of risk-taking at "The Spaceship Company". (Whether such a book is warranted or not.)
Does anybody know if it's common that an aircraft can be structurally compromised like that due to user error?
I can easily imagine the stress on the airframe doing manoeuvres like this, if I were a pilot I'd be absolutely terrified that it were possible for me to flip a switch and just have the vehicle I'm in disintegrate around me.
edit: whoops, commented on a day old thread, what a dingus
> “I can’t imagine the forces he must have experienced being thrown out of the aircraft,” Sventek, who spent 31 years in the U.S. Air Force, said in an interview.
Some initial impulse from the ejecting motion of the craft breakup, and then immediately after losing contact, the only net force should be the one from air drag due to the velocity. There is gravity, of course, but in free-fall, that force is balanced by your acceleration so you don't feel it. As you reach terminal velocity, it rises toward 1g.
That air drag would be a big force, though, when you're thrown into the air at the craft's velocity.
Did a little bit of a back of the envelop calculation on the subject, so this maybe completely bogus, be aware.
It would seem like the temperature that the pilot experienced upon ejection at Mach 1 at 15000m (when they broke apart) would be about -13C, which is reasonably survivable[1]. The pressure experienced is probably around 22kPa absolute, which in theory will generate anywhere between 6 - 20g[2]. Not pleasant, but survivable.
Given these, it takes a lot of luck to survive those conditions (1/5th atmosphere, extreme acceleration, low temperature when he falls), but it might be more survivable than we think (this is much better than exploding and ejecting at lower altitudes)
[1]: Calculation via the stagnation temperature at that speed for the standard condition at that altitude (Temperature ~= 217K, P ~= 12kPa)
[2]: Stagnation pressure on him in the front of the body (23kPa), ambient at the back. Average male body surface area is about 2m^2, depending on the geometry you might be able to get down to a quarter of that. Throw in the mass of the pilot (70kg? 90kg?), you should get accelerations in those ranges.
I doubt he got anywhere near 15g. As the pilot had a seat strapped to him when he was ejected, adding to his mass. On top of that I assume that he had much less surface area due to sitting down, although that one is much more speculative.
Your temperature is just plain wrong, the standard atmosphere model states -6.5°C per 1000m. This is means that the temperature was -97.5C below surface temp. So -70C is more likely.
The temperature experienced by the pilot as he was ejected was is calculated as the stagnation temperature (temperature on the surface of his clothing, or where the speed of the air = 0), which at Mach 1 would be around -12C. However this temperature will decrease as he slow down. Luckily it should take only about.. 45 seconds for him to get around 5000m, which becomes much more survivable.
Edit: from that page you linked, it says:
> Between 11 km and 20 km the temperature remains constant.
Hypothermia does provide some protection against hypoxia-induced brain damage. However, exposure to air at -13C for only a few minutes is very unlikely affect your core body temperature enough to cause hypothermia. And anyway, the time taken to fall from 15km to a more tolerable altitude would probably not be long enough to cause that type of damage in the first place.
While I agree it's useful to look at the bigger picture to avoid future mistakes. He pulled the switch, the buck stops with him. Could be fatigue, could be bad training, but ultimately for the purpose of the investigation it's human error.
If the pilot was at fault then the only unprofessional act would be to not state so. But likewise with any other deficiencies, from material sourcing to engineering process to flight operation.
This. At first, I wondered why the NTSB was getting all the design data from the company, much of which must be proprietary and, as a one-off custom design craft, not useful to the NTSB. I mean, wouldn't the company want to do its own research and find out what happened so it can fix it and resume flights? But then I realized that it's better for everyone if an outside party learns all it can and essentially debugs their design, like Feynman did with the space shuttle. One might even wonder if they aren't getting some highly expert aerospace consulting done for free.
That is not something I would ever want to experience.
I wonder how similar this environment is the the SR71 that disintegrated [1]. Luckily the SR71 pilots wore space suits with this happened. Otherwise I dont think he would have survived.
[1]http://www.916-starfighter.de/SR-71_Waever.htm