TGV Press Release on Test Firings

[Chris Bergin]

Only just sent to me (dated June 9), but here you go:

[meiza]

Vertical takeoff, vertical powered landing, 1000 kg to 100 km. Pressure fed, 6 engines. JP-8 jet fuel and I guess LOX.

[jongoff]

Chris Bergin - 12/6/2007  8:38 AM

Only just sent to me (dated June 9), but here you go:

Pat was one of the first people to realize the potential of the suborbital market for reusable vehicles.  They've been working away on this for several years, and have a pretty solid team put together.  Pat was in Mojave over at our shop for a short visit when he got the call about their first test.  He's a good guy, and it's good seeing that they're making some real progress.  

~Jon

[meiza]

1000 kg is a lot.

Wonder what their chamber pressure and ISP look like. Do they use copper regenerative engines? And what kind of injector? Throttling to 20% is deep.

[Crispy]

http://www.tgv-rockets.com/ but there's not much in the way of content

[jongoff]

Meiza,

1000 kg is a lot.

Yeah, they're in a totally different market segment from us.

Wonder what their chamber pressure and ISP look like. Do they use copper regenerative engines? And what kind of injector? Throttling to 20% is deep.

I'm not 100% sure on all that, but I do know that they're regen cooled, so they're probably using copper.  I have no idea what the Isp is, but I'm sure it's pretty good.  As for chamber pressure, they're doing pressure fed, and most pressure fed stages optimize out to a chamber pressure in the 150-300psi range.  Injector wise, I think they had a picture on their web that if you look real close showed a pintle injector.

~Jon

[braddock]

I did an interview with Pat Bahn of TGV Rockets as one of my first articles for this site:
http://www.nasaspaceflight.com/content/?cid=3679

Pat was very focused on the important practicalities of sub-orbital space flight - like fitting the rocket under highway bridges on the back of the truck.  Glad to see they are getting hardware firing.

[braddock]

That looks like a substantial engine... 30k lbs...

[savuporo]

1000kg @ 100km.
Could you build a LOX/Propane or LOX/LH2 stage with GLOW of 1000 kg that would make it to orbit from 100km ?

[meiza]

actually savuporo your max energy is at lower altitude, at first stage main engine cutoff. (You only add gravity losses by coasting to 100 km).
But I think a nearly SSTO stage would need to be done for that. Without taking air drag into account and assuming infinite T/W, you need about 500 m/s to reach 100 km, so that is not a big chunk of the 9 km/s delta vee needed for an orbital launcher.

In reality that is a somewhat bigger portion though. Orbital velocity is only about 7.8 km/s, and most of the losses occur during the first stage flight so in effect you might go from 9 km/s SSTO to a 8 km/s near-SSTO which is significantly easier.
With ISP 350 the mass ratio would drop from 13.7 to 10.3.

If you had 50 kg of payload, 50 kg of dry mass and 930 kg of propellants, that would do it.

More performance from first stage would be better, maybe a stage that peaked at a 300 km? I don't know the extent of thermal problems with various peak altitudes.

Ares I has an almost SSTO second stage since the first stage gives so little delta V (I don't know the peak altitude of the solid boosters).

[jongoff]

savuporo - 13/6/2007  2:54 AM

1000kg @ 100km.
Could you build a LOX/Propane or LOX/LH2 stage with GLOW of 1000 kg that would make it to orbit from 100km ?

Probably.  It's probably possible to have a 100kg GLOW stage reach orbit from 100km.  Just depends on how much payload you need.  XCOR, MSS, and TGV have all been looking at ideas along these lines.

~Jon

[meiza]

Big advantage is of course you can use a high expansion nozzle and get good ISP, and you don't have to worry much about aerodynamics. Also if you already have some upwards velocity when staging you don't necessarily need high T/W.

[jongoff]

meiza - 13/6/2007  9:27 AM

Big advantage is of course you can use a high expansion nozzle and get good ISP, and you don't have to worry much about aerodynamics. Also if you already have some upwards velocity when staging you don't necessarily need high T/W.

Exactly.  Lower T/W required makes it easier to hit the high mass ratio, cause you need less engine per unit mass of propellant.  It's also possible with a slightly higher performance suborbital booster to give the payload some downrange velocity then either perform an RTLS retroburn, or land somewhere downrange.

~Jon

[meiza]

Oh my god. I have been speaking complete reindeer crap.

If deltay = 0.5*g*deltat^2
and
deltat = deltav/g

then
deltay = deltav^2 / (2g)
and vice versa,
deltav = sqrt(2g*deltay)

So 100 km delta v is 1400 m/s, not 500 m/s! (I had a zero error, that's why my result was 3x too small)

Which makes a suborbital 100 km vertical hopper a much much better performer as a first stage than I first said.

Btw the Ares I solid burns out at 127 seconds, 192,000 feet and mach 6.08.
In sane units that is 60 km and 2100 m/s.

http://www.aerospaceweb.org/question/atmosphere/q0112.shtml is useful for mach conversions.

[braddock]

The Space Show just had an interview with Pat Bahn of TGV Rockets on Friday.

http://www.thespaceshow.com/detail.asp?q=780

Pat Bahn always has interesting, practical thoughts.

Their rocket uses standard JP-8 jet fuel, not RP1.  So they can fill up at any military base (sans LOX).

[simonbp]

meiza - 13/6/2007  4:09 AM

Ares I has an almost SSTO second stage since the first stage gives so little delta V (I don't know the peak altitude of the solid boosters).

IIRC, it's pretty much orbital; rather that diving the delta v in half over the stages (typical practice), the first stage is used for altitude and maybe 1-2 km/s of dv, while the upper stage provides the bulk of the dv at an altitude optimized for Isp. Incidentally, Shuttle and Ariane V do about the same,  as their orbiter/core stages minimally contribute to thrust before SRB burnout...

Simon

[Danderman]

Only just sent to me (dated June 9), but here you go:

So, what happened to these guys?

[AnalogMan]

Only just sent to me (dated June 9), but here you go:

So, what happened to these guys?

Last I heard, they got turned down for a CCDev-2 award two days ago.