Space Ship Two - General Thread

[vt_hokie]

I hope this isn't too OT but it's been bugging me for a while, how is it this vehicle is described as a space plane, yet something like an SR-72 which if it existed would probably fly just as high is called an aircraft? Is it the engines that mark the different definition between the two?

Use of RCS thrusters instead of aero surfaces for attitude control?  I agree, it gets to be kind of an arbitrary boundary.

[RonM]

I hope this isn't too OT but it's been bugging me for a while, how is it this vehicle is described as a space plane, yet something like an SR-72 which if it existed would probably fly just as high is called an aircraft? Is it the engines that mark the different definition between the two?

Use of RCS thrusters instead of aero surfaces for attitude control?  I agree, it gets to be kind of an arbitrary boundary.

The SR-71 Blackbird has a service ceiling of about 25 km. That is barely in the stratosphere. The Karman line, which Virgin Galactic is trying to reach is 100 km. That is in the thermosphere, which is a near vacuum. It's a big difference.

[savuporo]

The SR-71 Blackbird has a service ceiling of about 25 km. That is barely in the stratosphere. The Karman line, which Virgin Galactic is trying to reach is 100 km. That is in the thermosphere, which is a near vacuum. It's a big difference.

Maybe we should only start calling it a spacecraft AFTER it does get past Karman line. Which is still in doubt. X-15 is still mostly referred to as "rocket powered airplane" even though it did cross that line.

I propose a new term for all these unflown rocketships : WantToGoToSpaceCraft

[Star One]

I hope this isn't too OT but it's been bugging me for a while, how is it this vehicle is described as a space plane, yet something like an SR-72 which if it existed would probably fly just as high is called an aircraft? Is it the engines that mark the different definition between the two?

Use of RCS thrusters instead of aero surfaces for attitude control?  I agree, it gets to be kind of an arbitrary boundary.

The SR-71 Blackbird has a service ceiling of about 25 km. That is barely in the stratosphere. The Karman line, which Virgin Galactic is trying to reach is 100 km. That is in the thermosphere, which is a near vacuum. It's a big difference.

Just to clarify I wasn't talking about the SR-71 but the proposed SR-72.

http://www.lockheedmartin.co.uk/us/news/features/2013/sr-72.html

I saw some comment on aviation forums that if ever built it could operate close to the Karman line & that's the confusion I was referring to. This looks like it might have come out of the Falcon HTV which of course was rocket launched as a sub-orbital vehicle and was often called a spacecraft in the media so it seems a grey area.

[RonM]

I hope this isn't too OT but it's been bugging me for a while, how is it this vehicle is described as a space plane, yet something like an SR-72 which if it existed would probably fly just as high is called an aircraft? Is it the engines that mark the different definition between the two?

Use of RCS thrusters instead of aero surfaces for attitude control?  I agree, it gets to be kind of an arbitrary boundary.

The SR-71 Blackbird has a service ceiling of about 25 km. That is barely in the stratosphere. The Karman line, which Virgin Galactic is trying to reach is 100 km. That is in the thermosphere, which is a near vacuum. It's a big difference.

Just to clarify I wasn't talking about the SR-71 but the proposed SR-72.

http://www.lockheedmartin.co.uk/us/news/features/2013/sr-72.html

I saw some comment on aviation forums that if ever built it could operate close to the Karman line & that's the confusion I was referring to. This looks like it might have come out of the Falcon HTV which of course was rocket launched as a sub-orbital vehicle and was often called a spacecraft in the media so it seems a grey area.

Sorry, I misunderstood. I haven't read about the SR-72, thanks for the link.

Getting back to your question, it's a grey area as to what to call a vehicle. I guess you name it based on what you are trying to do. The Karman Line is a compromise, nice round number, instead of an actual division between aircraft operations and space.

[Star One]

It just gets very confusing, the XCOR Lynx is called a suborbital spacecraft? I am not sure I agree with that description because to my mind you could call the SR-72 a spacecraft if you used the same definition and to my mind it clearly isn't one.

[sdsds]

Of course von Karman was like a god of fluid dynamics for many good reasons. This distinction between what is atmospheric flight (the field of aeronautics) and what is spaceflight (the field of astronautics) is at the heart of his Karman line definition. 100 km is a convenience. The distinction he made was closer to what vt_hokie mentions above. It involves the effectiveness of aerosurfaces in the extremely thin upper atmosphere. This isn't just about attitude control. What von Karman noticed had to do with lift from wings in steady state flight. At a certain altitude, the speed required by a wing to maintain lift is above orbital velocity at that altitude.

[Vultur]

That definition doesn't seem especially relevant to a vehicle that just goes 'up-and-down' like a sounding rocket, the early Mercury missions, SS2 or Lynx, though.

I mean, there has to be SOME definition otherwise people will start calling rockets that go to 80,000 feet 'spaceflight', but... 

[docmordrid]

IIRC military officers are issued astronaut badges at 100 km, though in the 1960's it was 80 km.

[Star One]

IIRC military officers are issued astronaut badges at 100 km, though in the 1960's it was 80 km.

You're thinking of the X-15 pilots I presume.

It's this sliding scale on where space is to how some choose to define it that allows VG to use the space ship definition.

[parabolicarc]

I discussed issues with Virgin Galactic on the John Batchelor Show on June 11 and then on The Space Show with David Livingston on Monday. George Whitesides was on the Batchelor Show last night.

All these appearances are archived on The Space Show site. Links for those who want to listen:

Doug Messier, John Batchelor Show: http://www.thespaceshow.com/detail.asp?q=2261

Doug Messier, The Space Show: http://www.thespaceshow.com/detail.asp?q=2263

George Whitesides, John Batchelor Show: http://www.thespaceshow.com/detail.asp?q=2265

There's also The Space Show blog where you can make comments on my appearance there this week:

http://thespaceshow.wordpress.com/2014/06/17/doug-messier-monday-6-16-14/

[yg1968]

The John Batchelor show with George Whitesides:
https://www.youtube.com/watch?v=seMumEIVffw&feature=youtu.be

[sdsds]

Jeff Foust points out is has now been ten years since SpaceShipOne flew:
http://www.newspacejournal.com/2014/06/21/ten-years-after-spaceshipone-made-history-the-future-is-still-waiting-to-arrive/

[Olaf]

WhiteKnightTwo is in the air on the first flight since 6 month.
https://www.facebook.com/#!/virgingalactic?hc_location=timeline

[MoeMelek]

WhiteKnightTwo is in the air on the first flight since 6 month.
https://www.facebook.com/#!/virgingalactic?hc_location=timeline

I think this latest addition of methane and helium really puts the SS2 "reliable and simple" into doubt. The original claim was that the rocket engine was really simple and reliable, and they have had so many problems with it it's just becoming ridiculous. Adding methane and helium during different parts of the burn adds complexity and failure modes, and feels like 'patches' to a problem they should have avoided to begin with. They will now fly with a more complicated, unsafe, and expensive system.

Also I've always had my concerns about the shuttle cock design. Moving structures like landing gears are one of the most failure prone components of an airplane. The shuttle cock design is two big moving structures, and survival critical ones. Failure to move wings into shuttle cock configuration, or out of it, will mean loss of vehicle.

What is even more disturbing is that problems with the engine and shuttle cock occurred with SS1. The engine was not burning smoothly and sometimes big chunks of rubber were ejected through the nozzle. During one of the flights the shuttle cock also initially refused to retract. These issues should have been considered before just scaling up the design.

I'd really like to see Virgin Galactic succeed, but I really do have a bad feeling that the SS2 design is not a good one, and certainly not as safe and simple as advertised.

[sghill]

WhiteKnightTwo is in the air on the first flight since 6 month.
https://www.facebook.com/#!/virgingalactic?hc_location=timeline

I think this latest addition of methane and helium really puts the SS2 "reliable and simple" into doubt. The original claim was that the rocket engine was really simple and reliable, and they have had so many problems with it it's just becoming ridiculous. Adding methane and helium during different parts of the burn adds complexity and failure modes, and feels like 'patches' to a problem they should have avoided to begin with. They will now fly with a more complicated, unsafe, and expensive system.

Also I've always had my concerns about the shuttle cock design. Moving structures like landing gears are one of the most failure prone components of an airplane. The shuttle cock design is two big moving structures, and survival critical ones. Failure to move wings into shuttle cock configuration, or out of it, will mean loss of vehicle.

What is even more disturbing is that problems with the engine and shuttle cock occurred with SS1. The engine was not burning smoothly and sometimes big chunks of rubber were ejected through the nozzle. During one of the flights the shuttle cock also initially refused to retract. These issues should have been considered before just scaling up the design.

I'd really like to see Virgin Galactic succeed, but I really do have a bad feeling that the SS2 design is not a good one, and certainly not as safe and simple as advertised.

You've got some good points, but there is some hyperbole in your statement.
Yes, the new engine is riskier in some areas (more complicated), but it's safer in others (less stress-inducing vibration).
Yes, SS1 had shuttlecock problems.  But it was an experimental testbed, not a commercial airframe.  One presumes they took a harder look at this known potential failure point when designing SS2.
Yes, SS1 had chunks of rubber flying out the back.  It was expected even if it was a bit loud.

Personally, I think the pre-flight fuel handling and potential helium handling problems are going to add some logistics and schedule adherence headaches versus plugging in a solid fuel module prior to each flight, but they've obviously calculated that it's an expense they can and have to absorb, or they wouldn't have chosen this route.

[Borklund]

Don't forget that there are no ejection seats, no pressure (partial or otherwise) suits, no parachutes, no nothing for passengers.

[docmordrid]

Don't forget that there are no ejection seats, no pressure (partial or otherwise) suits, no parachutes, no nothing for passengers.

Neither do airliners, or in its day the Concorde.

[banjo]

could the shuttlecock system have a manual backup?  some sort of hand crank maybe.   i'd be happy knowing something could be done if the wings get stuck. 

[Borklund]

Don't forget that there are no ejection seats, no pressure (partial or otherwise) suits, no parachutes, no nothing for passengers.

Neither do airliners, or in its day the Concorde.

You're absolutely right, but airliners at the very least carry oxygen masks, and while the Concorde pushed the limits it would never go above 18000 meters and could rely on contingency hardware and procedures in the event of cabin pressure loss. Going above 18000 meters altitude without at the very least a pressure suit is an incredibly reckless risk IMO. From ignition through to gliding below 12-15 km, you will die before you or anyone else can do anything about it. It is nothing to sneeze at, especially given the nature of the beast (the SS2), so to speak. Think of the implications of a fatal accident.

If it ever flies passengers into space.