Virgin Galatic Spaceship Two down in the Mojave.
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I see your point wrt media, but judgements can be made on statements directly from NTSB https://www.ntsb.gov/investigations/...mojave_ca.html.
Evacuate, evacuate .....
Originally Posted by joema
Once the flight test phase is over, yet another problem in vehicles like SS2 or the shuttle is handling passenger escape
Once the flight test phase is over doesn't the vehicle become "just another commercial aircraft" - albeit somewhat specialised?
Why would inflight escape be any more of a consideration, for crew or passengers on this aircraft, than on any other commercial aircraft?
Though it may be a bit more practical than floor lighting and slides
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Locking System Architecture
There has been much speculation and questioning about the locking system and feathering system architecture. I would have no reason to presume that the SS2 architecture of these system is significantly different than the Architecture of the same systems in SS1. It is presumed that the changes that were instituted from SS1 to SS2 were driven primarily by the need for increased size. This meant that the cockpit and cabin size needed considerable up sizing, necessitating changes such as the escape system ( no more ejectible nose cone), dual controls and an enlarged rocket motor. SS1 was a tested/proven system within its design context - no reason to change it.
The only facts that we know about the architecture to-date, is that both systems were pneumatic and the locks have been described as "hooks". This fits completely with SS1 architecture. I suspect that the SS2 architecture was an enlarged and more robust version of the SS1, which is shown and described in detail in Scale Composite's patent application for same:
http://www.spacepatents.com/patented...pat7195207.pdf
Fig. 7-9
The only facts that we know about the architecture to-date, is that both systems were pneumatic and the locks have been described as "hooks". This fits completely with SS1 architecture. I suspect that the SS2 architecture was an enlarged and more robust version of the SS1, which is shown and described in detail in Scale Composite's patent application for same:
http://www.spacepatents.com/patented...pat7195207.pdf
Fig. 7-9
Last edited by RF4; 11th Nov 2014 at 09:52. Reason: Corrected link
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Virgin Galatic Spaceship Two down in the Mojave.
Thanks for that link. Answers a lot of questions!
Ps. I needed to search in Bing to find the patent number as the direct link didn't work.
Ps. I needed to search in Bing to find the patent number as the direct link didn't work.
I think anyone expecting this craft to be fully certified would be making a similar mistake to NASA made after 4 flights of the Shuttle. They will never make enough powered flights in the test program to certify it to the same standards as the well understood tropospheric sub Mcrit areas most of us operate in.
DARPA regularly have in-flight breakups of their experimental high Mach number vehicles. This is not an area that is well understood. Most space vehicles brute force their way through it with massive amounts of thrust rather than what Scaled are trying.
DARPA regularly have in-flight breakups of their experimental high Mach number vehicles. This is not an area that is well understood. Most space vehicles brute force their way through it with massive amounts of thrust rather than what Scaled are trying.
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Working Link for Post #261
Sorry about that ! The link for the SS1 architecture patent should be;
http://www.spacepatents.com/patented...pat7195207.pdf
http://www.spacepatents.com/patented...pat7195207.pdf
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I wonder if when the design was scaled up from SS1 to SS2, the locks went from a nice to have/safety feature to being absolutely vital to control the feathers in the critical Mach region. It’s clearly marginal, since the locks are not needed when the vehicle is slowing down through the same speeds after engine shut-down.
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WSJ: pilot's account
Wall St Journal reports:
The pilot was unaware the co-pilot had prematurely unlocked its movable tail surfaces, recalled falling out of the space plane as it was coming apart, then managing to unbuckle his seat belt before his parachute opened automatically.
The pilot was unaware the co-pilot had prematurely unlocked its movable tail surfaces, recalled falling out of the space plane as it was coming apart, then managing to unbuckle his seat belt before his parachute opened automatically.
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From Bloomberg news:
"The (surviving pilot's) last memory before passing out was the realization that the water on his tongue was boiling, according to NASA. Water boils at lower temperatures as pressure decreases."
Pilot Who Survived Space Crash Says Parachute Opened Itself - Bloomberg
"The (surviving pilot's) last memory before passing out was the realization that the water on his tongue was boiling, according to NASA. Water boils at lower temperatures as pressure decreases."
Pilot Who Survived Space Crash Says Parachute Opened Itself - Bloomberg
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"The (surviving pilot's) last memory before passing out was the realization that the water on his tongue was boiling, according to NASA. Water boils at lower temperatures as pressure decreases."
At NASA's Manned Spacecraft Center (now renamed Johnson Space Center) we had a test subject accidentally exposed to a near vacuum (less than 1 psi) in an incident involving a leaking space suit in a vacuum chamber back in '65. He remained conscious for about 14 seconds, which is about the time it takes for O2 deprived blood to go from the lungs to the brain. The suit probably did not reach a hard vacuum, and we began repressurizing the chamber within 15 seconds. The subject regained consciousness at around 15,000 feet equivalent altitude. The subject later reported that he could feel and hear the air leaking out, and his last conscious memory was of the water on his tongue beginning to boil.
Transonic regime during descent
RichardC10
since the locks are not needed when the vehicle is slowing down through the same speeds after engine shut-down.
since the locks are not needed when the vehicle is slowing down through the same speeds after engine shut-down.
thcrozier
I'd be very interested to know the altitude at which it goes subsonic on descent.
I'd be very interested to know the altitude at which it goes subsonic on descent.
The idea of the feather is that the aircraft is both stable and has high drag. (I am almost sure that everyone will know this already but not quite:-)
SpaceShipOne Pilot Report
SS1 simulator ride
"As we approached apogee, as indicated by the rate of climb, Jim Siebold, one of the SCALED test pilots who had taken over coaching me, called for feather deployment. I pulled a large lever under my left arm up to unlock the feather, waited until the TONU told me it was unlocked, then pulled the feather lever.
...
In the SS1, once in feather, the airplane is so stable and self-aligning that the pilot doesn’t have a thing to do but wait until it’s down to around 60,000 feet, when he puts it back in glider mode and he starts worrying about finding the airport.
The foregoing is a brilliant concept. It removes the single most terrifying and critical part of space flight. The SS1 never sees indicated re-entry speeds higher than about 130 knots even though mach numbers are approaching 3.2 so it never gets hot."
"As we approached apogee, as indicated by the rate of climb, Jim Siebold, one of the SCALED test pilots who had taken over coaching me, called for feather deployment. I pulled a large lever under my left arm up to unlock the feather, waited until the TONU told me it was unlocked, then pulled the feather lever.
...
In the SS1, once in feather, the airplane is so stable and self-aligning that the pilot doesn’t have a thing to do but wait until it’s down to around 60,000 feet, when he puts it back in glider mode and he starts worrying about finding the airport.
The foregoing is a brilliant concept. It removes the single most terrifying and critical part of space flight. The SS1 never sees indicated re-entry speeds higher than about 130 knots even though mach numbers are approaching 3.2 so it never gets hot."
I could root around for a while and get some numbers but there is likely someone here who knows what they are about and I propose to leave that to them.
Ah, coffin corner! Possibly an easy way to get some decent data.
According to the diagram on Coffin corner (aerodynamics) - Wikipedia, the free encyclopedia the U2's "mach limit" (pretty sure this is under mach 1) is 125 KIAS at 65,000 ft and 145 KIAS at 60,000 ft. In the case of SS1 then 130 KIAS therefore seems comfortably subsonic at 60,000 ft when the feather is unfeathered. Does anyone have any idea what the stall speed might be? That is, is there any need to go faster again?
If it is the case that the stall speed at 60,000ft is above 145 KIAS then the transonic flight regime could be avoided entirely during the feather stowed portion of the gliding descent to the landing.
Last edited by jimjim1; 13th Nov 2014 at 08:35. Reason: reformat quotes
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In the SS2 powered flight video below, the feather deployment (not unlock) command is given at very low speed.
It's interesting that the SS1 simulation has the unlock command very close to the feather command (which seems natural), while the as-flown SS2 sequence moved the feather unlock much earlier (at speed of Mach 1.4). This has been stated to be because they were concerned that an unlock failure would result in a dangerous situation later in the nominal, high-altitude (300,000ft) flight when the mission could not be aborted. So they removed a single-point failure (unlock failure) by moving it to earlier in the flight, but consequently added a new single-point failure of incorrect unlock actuation (at high speed).
It's interesting that the SS1 simulation has the unlock command very close to the feather command (which seems natural), while the as-flown SS2 sequence moved the feather unlock much earlier (at speed of Mach 1.4). This has been stated to be because they were concerned that an unlock failure would result in a dangerous situation later in the nominal, high-altitude (300,000ft) flight when the mission could not be aborted. So they removed a single-point failure (unlock failure) by moving it to earlier in the flight, but consequently added a new single-point failure of incorrect unlock actuation (at high speed).
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Originally Posted by RichardC10
So they removed a single-point failure (unlock failure) by moving it to earlier in the flight, but consequently added a new single-point failure of incorrect unlock actuation (at high speed).
However -- to my knowledge there has been only one reentry fatality related to flight control -- the Mike Adams X-15 flight on 15 Nov 1967: https://en.wikipedia.org/wiki/X-15_Flight_3-65-97
Although not widely reported at the time, Scott Carpenter's Mercury mission was a near fatality due to reentry control problems: Mercury Astronaut Scott Carpenter and the Controversy Surrounding Aurora 7 | Popular Science
However those are the only two. In retrospect it seems odd to make "care free" reentry such a fundamental design priority. Reentry is critical but it's just one phase. Flight control is always critical, whether inside or outside the atmosphere, or at reentry interface. SS1/SS2 have cold-jet RCS to provide active attitude control above the atmosphere, so it's not like the feather system eliminates that.
Furthermore VG's ultimate goal is using follow-on vehicles for point-to-point suborbital transport. However that requires nearly the same engines, velocity and thermal protection as orbital flight. It is unclear if the feathering system would work at orbital reentry speeds or whether VG has even done preliminary testing on this. If the experience gained on SS2 can't be used on that, it's a technological dead end.
There is an obvious attraction to passively safe systems. Engineers learn early that "complexity breeds failure". But as we see from this incident, even passively safe systems introduce their own complexity and tradeoffs.
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Rutan conceptually modeled it on the self-stabilizing badminton shuttlecock.
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However -- to my knowledge there has been only one reentry fatality related to flight control -- the Mike Adams X-15 flight on 15 Nov 1967: https://en.wikipedia.org/wiki/X-15_Flight_3-65-97
Off the top of my head, Columbia's first flight might well have burned up if they'd let the computer fly the re-entry, because the computer's aerodynamic model was wrong. Columbia's final flight was doing OK despite losing parts of the wing, until the drag exceeded the ability of the RCS to keep it pointed in the right direction. Not sure if you can count the Soyuz that re-entered backwards, since that was due to the service module failing to detach... but Soyuz, like Apollo was built to be aerodynamically stable with the heat shield pointing in the right direction, and could survive an uncontrolled re-entry that way, even if the crew might not be happy about the 10+g deceleration.
I would guess that 'feathering' was used on SS1 because it was much cheaper and faster to develop than an active system. I presume they did a similar cost/benefit analysis before deciding to use it on SS2.