VSS Enterprise completes first flight under its carrier aircraft

On 4/2/2010 4:07 PM, Jorge R. Frank wrote:

Worse, without the wings the fuselage would stabilize nose-first instead
of belly-first, resulting in high "eyeballs-out" G-force.

No, it wouldn't unless it was nose heavy to begin with.
In fact, it might stabilize tail-first due to the weight of the rocket
engine in the back end.
What I'm mainly concerned with is it tumbling on the way down to the
point where the g-forces cause it to come apart or kill the occupants*.
The chute concept is based on the airframe parachute system available
for small aircraft:http://en.wikipedia.org/wiki/Ballistic_Recovery_Systems

* In the case of people who have fallen from airliners breaking up at
high altitude, the spin rate can become so severe as to rip their arms
and legs off from the centrifugal forces generated.

Pat

Pat Flannery wrote:

On 4/2/2010 3:59 PM, Fevric J. Glandules wrote:
or the rocket engine blowing up for that matter.

IIRC from Mike Melville's presentation there's about zero chance
of that happening.

"About zero", I like that.
He's still using one of those Pentium 486DX chips in his computer, isn't
he? :-D
Let's see...total area of Northern Atlantic Ocean...total area of
Northern Atlantic Ocean covered with icebergs on great circle route from
Southampton to New York City in April...oh hell, it will be nearly
completely safe.

grin

Point taken. *However*, because this is Usenet, and the fat lady
*never* sings, my understanding of the motor design is that it
simply *can't* blow up.

It's just a control surface that's slightly larger and has a
greater degree of movement than we're used to - no?

No, it's the entire tail boom with the vertical and horizontal control
surfaces on it, with the closest analogy being to the folding wing on a
naval aircraft or the swing wing on a F-14 or F-111.

The swing wing analogy is apt. (The other is not). I've never heard of
a swing wing failing to swing.

I'm not worried about it running into something up there, but rather

snip

Valid concerns, but nothing that isn't, as I see it, bog-standard [1]
engineering.

It will never be zero-risk, but the risk *can* be engineered down
to acceptable levels at an acceptable price. And Burt Rutan strikes
me as the sort of person that can do this.

[1] http://www.phrases.org.uk/meanings/bog-standard.html

On 4/3/2010 6:55 AM, Neil Gerace wrote:

I don't know whether any airliners have escape systems for passengers
that can work while the plane is in the air. If this is so, I see no
reason for a passenger-carrying spacecraft to have them. Other than
politics.

The thing is, everyone seems to be thinking about it like a airliner or
a business jet.
It's nothing like those; it's a rocket-powered transatmospheric vehicle
that is air launched, flies faster than a SR-71, climbs out of and
reenters the atmosphere, and performs a glide landing.
This thing's closest analogy isn't a Lear Jet, it's the X-15, and
flights of the X-15 were not taken lightly by anyone involved.

Pat

On 4/3/2010 3:24 PM, Fevric J. Glandules wrote:
Pat Flannery wrote:

On 4/2/2010 3:59 PM, Fevric J. Glandules wrote:
or the rocket engine blowing up for that matter.

IIRC from Mike Melville's presentation there's about zero chance
of that happening.

"About zero", I like that.
He's still using one of those Pentium 486DX chips in his computer, isn't
he? :-D
Let's see...total area of Northern Atlantic Ocean...total area of
Northern Atlantic Ocean covered with icebergs on great circle route from
Southampton to New York City in April...oh hell, it will be nearly
completely safe.

grin

Point taken. *However*, because this is Usenet, and the fat lady
*never* sings, my understanding of the motor design is that it
simply *can't* blow up.

It relies on generating internal pressure to achieve its thrust, which
means it can have the fuel casing rupture and explode.
Also, the nitrous oxide needs to be fed under pressure into the solid
fuel casing to work, so the nitrous oxide tank needs to be pressurized
also...and that can rupture.
If overheated or through coming into contact with substances that can
easily be oxidized, nitrous oxide will explosively decompose into high
pressure oxygen and nitrogen gas, as they found out the hard way back in
2007 during the ground tests of the engine:
https://www.newscientist.com/article...a-mystery.html
Although Scaled Composites says it's "benign":
http://www.virgingalactic.com/overview/safety/
It is no more benign than hydrogen peroxide, which shares the same
characteristics, as it will decompose into high temperature steam and
oxygen gas if overheated or exposed to a substance it can oxidize.

Pat

On 4/2/2010 3:59 PM, Fevric J. Glandules wrote:
The primary reason for choosing Mach 2.02 as the max cruising speed was
to allow the airframe to be built out of aluminum alloys, at speeds
higher that heating was severe enough to require stainless steel or
titanium construction, and the development costs would go through the roof.

Exactly my point. Costs dictated maximum speed, which dictated
altitude, not concerns about being above "blood-boiling altitude".

There would be another factor that would argue against flying at
higher altitudes, and that's the choice of fuel.
The SR-71 used JP-7 to prevent fuel boiling at full altitude and the U-2
JPTS for the same reason.
Both of these were considerably more expensive than the standard fuels
used by jet airliners, and would have limited availabilty at airports as
well.

Pat

Pat Flannery wrote:

The thing is, everyone seems to be thinking about it like a airliner or
a business jet.
It's nothing like those; it's a rocket-powered transatmospheric vehicle
that is air launched, flies faster than a SR-71, climbs out of and
reenters the atmosphere, and performs a glide landing.

Of course that's right, so society (through the FAA or its counterparts in different countries) can insist that anyone
who flies Virgin Galactic is told about all the known hazards. I don't know, but I expect this did happen with X-15 crews.

Pat Flannery wrote:

[motor blowing up]

If overheated or through coming into contact with substances that can
easily be oxidized, nitrous oxide will explosively decompose into high
pressure oxygen and nitrogen gas, as they found out the hard way back in
2007 during the ground tests of the engine:

Point made.

Neil Gerace wrote:

Of course that's right, so society (through the FAA or its counterparts
in different countries) can insist that anyone who flies Virgin Galactic
is told about all the known hazards. I don't know, but I expect this
did happen with X-15 crews.

They were test pilots - it was their job to find out what the *unknown*
hazards were.

On 4/4/2010 6:53 AM, Neil Gerace wrote:
Pat Flannery wrote:

The thing is, everyone seems to be thinking about it like a airliner
or a business jet.
It's nothing like those; it's a rocket-powered transatmospheric
vehicle that is air launched, flies faster than a SR-71, climbs out of
and reenters the atmosphere, and performs a glide landing.

Of course that's right, so society (through the FAA or its counterparts
in different countries) can insist that anyone who flies Virgin Galactic
is told about all the known hazards. I don't know, but I expect this did
happen with X-15 crews.

I'm sure they knew that the thing was a bit dangerous. ;-)
It just occurred to me that the two share something else in common; both
have suffered a oxidizer tank explosion while their rocket engine was
under ground test:
http://www.youtube.com/watch?v=WXpEPZ6ZZIs

Pat

On 4/4/2010 8:15 AM, Fevric J. Glandules wrote:
Neil Gerace wrote:

Of course that's right, so society (through the FAA or its counterparts
in different countries) can insist that anyone who flies Virgin Galactic
is told about all the known hazards. I don't know, but I expect this
did happen with X-15 crews.

They were test pilots - it was their job to find out what the *unknown*
hazards were.

I guarantee you they weren't expecting the nose gear to start deploying
all on its own at Mach 3.4...or Mach 4.2...or Mach 5.2:
http://www.sierrafoot.org/x-15/adven...dventures.html
The problem was the nose gear was extended by pulling on a cable
attached to a handle in the cockpit, that opened a scoop on the nose
gear doors - causing air to enter the scoop and pressurize the nose gear
bay to blow the doors open...as the fuselage heated up in flight it
stretched in length from the expansion of the metal, while the cable
didn't heat up, so it stayed the same length, pulled taut, and activated
the scoop.

Pat