Virgin Galactic and SpaceShipTwo Master Thread (1)

[thomson]

FWIW, Sir Richard Branson was on CNN this evening, claiming that VG might be going orbital in the next 5 - 6 years, with a Virgin Space Hotel down the road.

Any chances anyone recorded that? Is this interview or speech available on-line somewhere?

[yg1968]

George Whitesides:
http://www.marketwatch.com/video/asset/markets-hub-virgin-galactic-ceo-on-space-tourism/E0D58C26-5E82-4571-851A-FFA6B353D263

[simonbp]

...and you have no possibility of "gas and go" operation (no, casting a new propellant load and loading it isn't gas and go). I fail to see the advantages. Either go solid or go liquid.

Well, you don't cast a new piece of rubber after each flight, you cast a whole bunch and put them in a warehouse. They're pretty inert, and quite safe to stockpile. N2O is dangerous stuff (as Scaled has tragically learned), but I'm still not convinced it's more dangerous than LOX or Peroxide.

The real advantage when Scaled started up working on the X-Prize was that no appropriate liquid rockets existed, and to develop one was way too expensive. SpaceDev offered a cheap hybrid with most of the advantages of a liquid, and Scaled too them up.

And as far as turn-around time, the last two (prize-winning) flights of SS1 were within a week of each other (so as to allow three flights in the two-week window). Propellant loading constituted a minuscule amount of that time, and it's not had to image a flight rate of once per day, which is likely more than enough for the current demand...

[HMXHMX]

...and you have no possibility of "gas and go" operation (no, casting a new propellant load and loading it isn't gas and go). I fail to see the advantages. Either go solid or go liquid.

Well, you don't cast a new piece of rubber after each flight, you cast a whole bunch and put them in a warehouse. They're pretty inert, and quite safe to stockpile. N2O is dangerous stuff (as Scaled has tragically learned), but I'm still not convinced it's more dangerous than LOX or Peroxide.

The real advantage when Scaled started up working on the X-Prize was that no appropriate liquid rockets existed, and to develop one was way too expensive. SpaceDev offered a cheap hybrid with most of the advantages of a liquid, and Scaled too them up.

And as far as turn-around time, the last two (prize-winning) flights of SS1 were within a week of each other (so as to allow three flights in the two-week window). Propellant loading constituted a minuscule amount of that time, and it's not had to image a flight rate of once per day, which is likely more than enough for the current demand...

LOX isn't a monopropellant; N2O and H2O2 are.

And Burt made the decision to use a hybrid long before SpaceDev was involved.  The memo suggesting it to him was written in 1996.  SpaceDev and EAC competed for the Scaled development contract in 2002.

Hybrids were the right choice for SSO, but not for SS2.  Yes, they have the advantages of both solids and liquids, but they also have the disadvantages, as well.  They have their place for experimental vehicles, but not for operational ones.

[Garrett]

George Whitesides:
http://www.marketwatch.com/video/asset/markets-hub-virgin-galactic-ceo-on-space-tourism/E0D58C26-5E82-4571-851A-FFA6B353D263

Thanks for that link. OK, so 2013 it is then for commercial flights. I'm impatient, but I do realize how far they've come.

[Garrett]

Just for some space geeky fun, I created a Gantt chart outlining the evolution of SpaceShipTwo's development.
It's based on real data, estimations, wild speculation, and hopes and dreams.

Use with caution.
Cheers!

[Phillip Clark]

Forgive me if this is a really stupid question, but wouldn't Skylon work as well for Virgin as contemporary passenger planes like the 747 do for Virgin Airlines?  I don't remember seeing the two considered together.

I wasn't aware that Alan Bond/Reaction Engines were considering Skylon as a manned launcher.   Maybe I am out-of-date, of course!

[HIP2BSQRE]

...and you have no possibility of "gas and go" operation (no, casting a new propellant load and loading it isn't gas and go). I fail to see the advantages. Either go solid or go liquid.

Well, you don't cast a new piece of rubber after each flight, you cast a whole bunch and put them in a warehouse. They're pretty inert, and quite safe to stockpile. N2O is dangerous stuff (as Scaled has tragically learned), but I'm still not convinced it's more dangerous than LOX or Peroxide.

The real advantage when Scaled started up working on the X-Prize was that no appropriate liquid rockets existed, and to develop one was way too expensive. SpaceDev offered a cheap hybrid with most of the advantages of a liquid, and Scaled too them up.

And as far as turn-around time, the last two (prize-winning) flights of SS1 were within a week of each other (so as to allow three flights in the two-week window). Propellant loading constituted a minuscule amount of that time, and it's not had to image a flight rate of once per day, which is likely more than enough for the current demand...

LOX isn't a monopropellant; N2O and H2O2 are.

And Burt made the decision to use a hybrid long before SpaceDev was involved.  The memo suggesting it to him was written in 1996.  SpaceDev and EAC competed for the Scaled development contract in 2002.

Hybrids were the right choice for SSO, but not for SS2.  Yes, they have the advantages of both solids and liquids, but they also have the disadvantages, as well.  They have their place for experimental vehicles, but not for operational ones.

So what engine would you have suggested/developed???  What do you think that they should do now?

[Cinder]

Forgive me if this is a really stupid question, but wouldn't Skylon work as well for Virgin as contemporary passenger planes like the 747 do for Virgin Airlines?  I don't remember seeing the two considered together.

I wasn't aware that Alan Bond/Reaction Engines were considering Skylon as a manned launcher.   Maybe I am out-of-date, of course!

They mainly don't, but a passenger module gets mentioned every now and then.  I think Mr Hempsell mentioned it here at NSF once or twice, saying it was possible but not saying much more than that.

I think at this point they want Skylon to prove itself and then pax'll be something of a formality.

[docmordrid]

If not hybrid, I'd go down the road to XCOR and see if one of their methane engines could be scaled up or if a cluster could work.

[john smith 19]

Forgive me if this is a really stupid question, but wouldn't Skylon work as well for Virgin as contemporary passenger planes like the 747 do for Virgin Airlines?  I don't remember seeing the two considered together.

They mainly don't, but a passenger module gets mentioned every now and then.  I think Mr Hempsell mentioned it here at NSF once or twice, saying it was possible but not saying much more than that.

I think at this point they want Skylon to prove itself and then pax'll be something of a formality.

RE have done a couple of reference designs. 1 was for something like 4 people with a block of cargo for delivery to ISS (including a payload bay airlock module like the Shuttle to allow entry). The other was IIRC for a larger group of 14 or 24 for delivery to a more convenient site for example a space hotel.

RE's aim is to offer Skylon and let people use it as they want. They don't want to be a space line.

Note that Virgin Galactic are not the company who are developing SS2. VG does not want to be in the aerospace business as a manufacturer.

VG take the view that if someone offers them a design that's better than what they have (and they have enough demand to justify it) they'd buy one. Or lease one (which is I think how most general aviation aircraft are acquired these days).

[kevin-rf]

A bit of a side topic but there is an interesting article in flightglobal about Burt Rutan and his designs.

http://www.flightglobal.com/articles/2011/07/14/359486/rutans-risky-business.html

Aviation legend Dick Rutan is not criticising his younger brother when he says the aerodynamic ideas of the now-retired founder of Scaled Composites are generally wrong two times out of three.

[Rocket Science]

If not hybrid, I'd go down the road to XCOR and see if one of their methane engines could be scaled up or if a cluster could work.

Right on doc... just like the old XLR-11 twin pack!
Robert

[HMXHMX]

If not hybrid, I'd go down the road to XCOR and see if one of their methane engines could be scaled up or if a cluster could work.

Right on doc... just like the old XLR-11 twin pack!
Robert

You'd need quite a cluster, since SS2 needs about 30 tons of thrust.

[simonbp]

You'd need quite a cluster, since SS2 needs about 30 tons of thrust.

Well, then you'd need about twenty of the Lynx RP-1 engines, or eight of the 7,500 lbf ATK CH4 engines, or two of the ULA LH2 engines. A Merlin at 50% thrust could do it too...

Still, considering Lynx is getting away with only four engines, does SS2 really need five times the thrust? Especially considering the prop mass will go down considerably with liquid engines?

[Rocket Science]

Anyone have one XLR-99 engines laying around in some warehouse somewhere?

[Jason1701]

Anyone have one XLR-99 engines laying around in some warehouse somewhere?

I know where an XLR-11 is laying around; we just need to find four more!
(It's in a lab in Princeton.)

[HMXHMX]

You'd need quite a cluster, since SS2 needs about 30 tons of thrust.

Well, then you'd need about twenty of the Lynx RP-1 engines, or eight of the 7,500 lbf ATK CH4 engines, or two of the ULA LH2 engines. A Merlin at 50% thrust could do it too...

Still, considering Lynx is getting away with only four engines, does SS2 really need five times the thrust? Especially considering the prop mass will go down considerably with liquid engines?

Yes, it needs the thrust.  Burnout has to occur in sensible atmosphere in order to retain control authority, just like SSO.

[Rocket Science]

The Canadian Arrow project of a few years back was based on the German V-2 technology rocket. It was a nice KISS approach. Why not try that approach with the later development that went into the man rated Redstone engine. A modern version could be a nice simple solution and with relatively sane (for rocket propellants) alcohol/oxygen.
Regards
Robert
http://www.universetoday.com/9055/canadian-arrows-engine-tested/

[HMXHMX]

VG doesn't have an engine issue.  They have a propulsion system problem.  I once created a paraphrase of the old military truism: "Amateurs argue about tactics; professionals talk about logistics."  My paraphrase replaces "tactics" with "engines" and "logistics" with "pressurization systems."  (No offense meant to amateurs, truly....)

Pressurization costs about $2 for every $1 spent on the engine (I've found the hard way).  For SS2, there are additional considerations that generally aren't as significant or even applicable for a conventional rocket, such as Cg, ride comfort, human safety and turn time.

This observation applies to a pressure-fed option, rather than a pump-fed one, but I'd bet long odds that the pump will cost you more than the ratio in the above example. 

VG could adopt an existing pump fed engine if there was one available in the right thrust class (there is, but I'm not saying) or they can start over from scratch and buy/build a new system.