SpaceShipTwo

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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paperburn1
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Re: SpaceShipTwo

Postby paperburn1 » Wed Nov 12, 2014 1:13 am

The time from unlocking the wing fold mechanism to total loss of telemetry was less than 2 seconds. That is a point of record. Or to put it another way before you said Mississippi it was gone.
I am not a nuclear physicist, but play one on the internet.

D Tibbets
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Re: SpaceShipTwo

Postby D Tibbets » Wed Nov 12, 2014 3:34 am

Expanding on what DeltaV said, it occurs to me that the feathering system was perhaps intended to be passive. If I'm not too far off, the locking lever prevented feathering with a mechanical lock. Once released a spring or other uncontrolled actuator may swing the tail around, aerodynamic pressures permitting. Once supersonic and accelerating under rocket thrust, the air flow might keep the tail in the non feathered position passively. Once acceleration is cut off and/ or there is negligible air flow over the tail, the unresisted deployment proceeds. There is a backup active control to deploy the feathering tail if needed, but normally it is only a backup. It was presumably recognized that transonic air flow might/ would not provide the restraining air flow over the tail, so provision was made for locking the tail down till this regime was passed. If this is the case, then pulling the lever early was a devastating error. Pilot training is one thing, Murphy's law is another. That such a devastating but easily made error might occur should have been buffered against. A simple delay built into the lever, so that actuation would take a few seconds to cycle, of a computer lockout till supersonic would serve. This adds complexity and further considerations of faults and counters, but in hindsight, the simple approach proved fatal- if my train of thoughts is reasonable.

Dan Tibbets
To error is human... and I'm very human.

Giorgio
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Re: SpaceShipTwo

Postby Giorgio » Wed Nov 12, 2014 9:54 am

The notion of unlocking at mach 1.4 was probably based on the ideas that:

1) they are far away from Transonic Regime issues and
2) the rocket would have reached that speed only at an altitude where aerodynamic pressure would have been negligible.

To put everything in perspective, the air density at launch altitude (50.000 ft) is in the range of 0,3 Kg/M3, while when reaching mach 1,4 speed (we can estimate at least 120.000 ft altitude) the density would have been only 0,003 Kg/m3. That is a reduction of 100 times in the dynamic pressure involved on the craft.

I would love to know what it the Maximum-q "altitude and speed" design for the Spaceship2. It could give a more clear picture to the whole situation.
A society of dogmas is a dead society.

paperburn1
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Re: SpaceShipTwo

Postby paperburn1 » Wed Nov 12, 2014 11:30 pm

We also need to keep in mind a large number of test flights were centered around mach and airspeed flutter susceptibility envelope expansion.In my mind this shows that they were aware of the problem also shows to me that they believe they had discovered the solution to the problem by the flight profiles and testing that they had done. As much as I hate to say it this looks like a simple pilot error. He unlocked the tail plane controls early, the aerodynamic forces in the transonic range overrode the controls and tore the airplane apart. To put it very simply the boom part of the sonic boom was probably over the control surfaces when he unlocked them in it overrode the hydraulics.
I am not a nuclear physicist, but play one on the internet.

D Tibbets
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Re: SpaceShipTwo

Postby D Tibbets » Wed Nov 12, 2014 11:38 pm

To continue my speculations, which are worth as much as I am getting paid for them...

I uspect that the initial rocket acceleration is at nearly level attitude (no climb in altitude), Once the lever is released, the tail starts to elevate under some internal pressure such as a spring or programed hydrolic pressure. This is resisted by the air flow, and the final result is a passive gradual change in attitude to a nearly nose up- vertical climb. No pilot or flight control inputs are needed. It is an elegant stable flight profile. Once near vertical attitude is achieved, the craft has climbed to much higher altitude, and aerodynamic forces are trivial- it doesn't matter that the tail is feathered, the only action may be arobraking, not aircraft attitude change. The positive Gs from rocket thrust could also impeed the full deployment of feathering untill thrust was cut off. If this possibly foolproof flight condition was used, the only pilot or auto pilot inputs would be necessary if something failed- like the tail got stuck. The weak point in retrospect may have been the active input that was necessary during early flight when transonic conditions precluded the otherwise stable configuration of a freely moving tail (thus locked down). The descent might also utilize some passive response of the tail feathering position, though again when it slowed to near transonic speeds, some active input might be required to move and lock the tail to straight back position. In this vague picture, the pilot inputs would be to initially launch, fire the rocket, release the tail lock (at the appropriate time), control any unwanted role, and otherwise standby for any other interventions that might be necessary till reentry was nearly complete, then at some point locking the tail back down and gliding to landing. Transonic conditions may not be an issue with the craft fully feathered, and at higher altitude(?), and without thrust. It might transition naturally to a tail level attitude at some point. Such a design would certain be elegant and highly resistant to disruptions or failures, except of course for that one critical period.

Was the rocket kick too disorienting, or was it an Evil Kineval event, or a combination of both?
Evil Kinevel tried to ride a steam powered rocket across the Snake River (?) canyon in the 1980s. He had his hand on the parachute release and planed to pull it ~ 1/2 way across, but instead yanked it with the initial rocket firing. So, instead of jumping across the canyon, he jumped into it.

Dan Tibbets
To error is human... and I'm very human.

paperburn1
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Re: SpaceShipTwo

Postby paperburn1 » Thu Nov 13, 2014 12:26 am

SS2 carries up to 6 passengers and two crew and utilizes a hybrid rocket engine for ascent and a unique glider mechanism on descent. It is carried to an altitude of 50,000 feet by a highly modified, all carbon-fiber, dual fuselage airplane, the VirginMotherShip Eve, where it free falls for 5 seconds before igniting its hybrid engines. After reaching a maximum altitude of 360,000 feet, SpaceShipTwo deploys its unique feathering wings to maintain stability as it glides back to Spaceport America. This unique flight profile will enable VG to conduct multiple flights per day if needed. In addition, VG has constructed one of the first fully commercial spaceports, called Spaceport America in New Mexico that will service its fleet of aircraft and spacecraft. VG’s mission to open up spaceflight to the masses poses unique aeromedical challenges that will require dedicated research and clinical efforts to help establish best-practice guidelines to ensure the safety of passengers and minimize the risk of in-flight events.
SpaceShipTwo
Inaugural Launch Date 2014
Acceleration Profile Max Gx 6.0, Max Gz 3.8
Passenger capacity 6 passengers, 2 crewmembers
Life Support System None, shirt-sleeve
Crew Worn Equipment TBD
Destinations Sub-orbital, parabolic profile
Reusable Yes, multiple flights daily
The Flight Plan
As planned, a Virgin Galactic trip to space lasts about 90 minutes. For the first 45 to 60 minutes, WhiteKnightTwo flies in a corkscrew pattern, gaining altitude. At about 50,000 feet, WhiteKnight2 unhooks SpaceShipTwo, naturally pulls up because of the dropped weight, and gets out of the way. After free falling for three seconds, SpaceShipTwo fires its engine and turns straight up. “You’re forced back in your seat and there’s this howling noise behind your head, you get a little bit of vibration,” Mackay says. “It’s actually smoother than I expected it to be. But it’s a tremendous acceleration.” This is the only new territory for the Virgin pilots, most of whom don’t have experience in space. To make sure they’re ready for the heavy G forces, they get weekly flights in an Extra 300 acrobatic plane that does spins and tumbles.

After a minute of rocket-powered flight, which delivers 3Gs to the chest, the rocket cuts off. The pilots use the ship’s feathering system to flip it upside down, for a simple reason: The windows are mostly near the top of the cabin, and they believe the passengers will be most interested in looking down at the planet they’re leaving behind. At this point, the passengers and crew are 150,000 feet up, nearly out of the atmosphere, and SpaceShipTwo coasts upward a few more hundred thousand feet, hitting three times the speed of sound.

Like any object thrown into the air, SpaceShipTwo follows a parabolic curve and falls back to Earth. Passengers get about four minutes to float weightlessly around the cabin. That time would be longer if SpaceShipTwo were flying faster, but Virgin compromised to minimize the G forces on its customers. The plan for getting them back in their seats is pretty simple, says Beth Moses, Virgin Galactic’s astronaut trainer: “You hope they have enough survival instinct” and follow pilots’ instructions to strap on their five-point harnesses before gravity kicks in. The pilots are strapped in the whole time, but “we might look out the window and admire the view as well,” Mackay says.

While SpaceShipTwo is out of the atmosphere, it can be controlled with small jets on the nose and wings that fire compressed air. The goal, however, is to use them as little as possible, to avoid interfering with the passenger experience. No matter the angle at which the ship reenters the atmosphere, the feathering system will flip it into the correct position with the belly parallel with the Earth’s surface, but the pilots plan to get it properly oriented beforehand using those jets, to make things more comfortable for the passengers. So on top of all the aerospace challenges the Virgin pilots deal with, they have to worry about the comfort of the wealthy tagalongs in the back of the ship.

Then it’s up to the pilots to get back onto the runway. They exactly one shot at getting it right, since SpaceShipTwo at this point is unpowered—there’s no pulling up and circling around if they screw up the approach angle. Again, that’s where hiring the planet’s best pilots is a big help: These guys have spent their lives flying high-performance aircraft.
I am not a nuclear physicist, but play one on the internet.

GIThruster
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Re: SpaceShipTwo

Postby GIThruster » Thu Nov 13, 2014 6:53 pm

Not sure who wrote this, but I hardly think it;s fair to say VG constructed Spaceport America. It's a public project built and maintained by the State of New Mexico government. VG just built the first terminal there.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

paperburn1
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Re: SpaceShipTwo

Postby paperburn1 » Thu Nov 13, 2014 10:52 pm

It came from a web site for flight surgeons and space medicine
I am not a nuclear physicist, but play one on the internet.


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