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SpaceShipTwo's Rocket Engine Did Not Cause Fatal Crash
astroengine writes It wasn't SpaceShipTwo's hybrid rocket motor — which was flying on Friday with a new type of fuel — that caused the fatal crash, the head of the accident investigation agency said late Sunday. The ship's fuel tanks and its engine were recovered intact, indicating there was no explosion. "They showed no signs of burn-through, no signs of being breached," Christopher Hart, acting chairman of the National Transportation and Safety Board, told reporters at the Mojave Air and Space Port in Mojave, Calif. Instead, data and video relayed from the ship show its hallmark safety feature — a foldable tail section designed for easy re-entry into the atmosphere from space — was deployed early, causing the in-flight break-up.
Because you do not need to be anywhere near orbital velocities for friction to be an issue. The SR-71 cruises at around 1/9th orbital velocity and had a lot of heat issues to deal with.
It needs the foldable tail to create a stable, high drag configuration to get it safely down to denser air.
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Normally, the feather system wouldn’t be unlocked until the rocket-powered spaceship is moving about Mach 1.4, or 1.4 times faster than the speed of sound. Instead, the co-pilot moved the lever from locked to unlock when the spaceship was traveling at about Mach 1, Hart said. “I’m not stating that this is the cause of the mishap,” he added. “We have months and months of investigation to determine what the cause was.” In addition to the possibility of pilot error, Hart said the NTSB is looking a variety of other issues that may have caused or contributed to the accident
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The main issue is the aerodynamic forces are enough that if you aren't pointed in the right direction it could destroy the aircraft. The worry was during reentey but if this report is correct it shows you how the wrong orientation can cause breakup.
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Because the foldable tail puts into a very stable configuration, removing the need for attitudinal jets, because reasonable sized flaps would not work in the very thin atmosphere.
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Eh? No, the crew of Columbia did not survive all the way down. Perhaps you are thinking of challenger, where there is some debate on if they survived until impact. In the case of Columbia the crew was dead four times over before impact. The lethal factors NASA identified were:
1. Depressurization of the crew module at or shortly after orbiter breakup.
So, we start with denying the crew oxygen. None closed their helmets when pressure dropped to 0 in a fraction of a second at the start of the breakup.
2. Exposure of unconscious or deceased crew members to a dynamic rotating load environment with a lack of upper body restraint and non-conformal helmets.
Then we bang them around a bit in what can be best described as a rolling garbage compressor full of sharp and heavy things, in helmets not designed to protect against this kind of force and without proper seat belts.
3. Separation of the crew from the crew module and the seat with associated forces, material interactions, and thermal consequences.
Then we break the box apart, exposing the crew to an unprotected reentry into atmosphere
4. Exposure to near vacuum, aerodynamic accelerations, and cold temperatures.
Finally we let them free-fall back to earth...
The Columbia Crew Survival Investigation Report is a 400 page long and very dark document, but the executive summary is just a couple pages. You can find it here:
http://history.nasa.gov/columb... The bodies of the astronauts were mangled beyond recognition, which is hinted in the report, but out of respect of the astronauts details of the injuries are redacted from the report.
Why does it need a foldable tail? Its not like it reenters at orbital velocities...
Because it assists with the descent. The craft falls back to earth something like a badminton shuttlecock. Not a perfect analogy but it's a fairly clever way to ensure flight stability in a very simple manner.
Indeed. From The Guardian:
Christopher Hart, the acting chairman of the US National Transportation Safety Board, told a press conference on Sunday night that the co-pilot, Michael Alsbury, had unlocked the feathering system, but that the second stage of the process, which moves the wings into the feathering position, happened “without being commanded”.
And here's a short video from the press conference.
the video seems to state:
1) SOP is to unlock at 1.4
2) the co-pilot moved the lever to unlock at 1.0
"the lock unlock is not to be moved into the unlock position until acceleration up to mach 1.4. Instead, that occurred at approximately mach 1.0"
http://www.bbc.co.uk/news/worl... (2:50)
I don't know if that difference is significant. It sounded to me like 'we're not casting blame formally yet, but look over here at this pilot error'
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Unless I'm missing something, the Columbia event had nothing to do with the SRBs