Comments on: Random Thoughts/Orbital Access Methodologies VII: Air-Launched Glideforward TSTO with Exo-atmospheric Suborbital Refueling

By: Martijn Meijering

Martijn Meijering — Mon, 05 Apr 2010 10:50:02 +0000

According to this link http://rt.com/Russia_Now/Russiapedia/Those_Russians/tkonstantin-tsiolkovsky.html Tsiolkovsky himself considered suborbital propellant transfer for launch applications! He apparently thought it was necessary to reach orbit. The article doesn’t give a time frame so it’s not clear if he beat Baron von Pirquet to the idea of propellant transfer.

By: Jonathan Goff

Jonathan Goff — Tue, 24 Nov 2009 21:12:24 +0000

Tim,
Higher pressures are mostly useful at low altitudes (where they allow you to takeoff with a bigger nozzle expansion ratio). At higher altitudes like you would get with an air launched stack, it’s only a second order benefit. You get more thrust out of the engine, but the Isp gain is pretty small. That said, you’d want to run a sim to actually quantify the benefit, to guide you on whether or not it’s worth the hassle.

~Jon

By: Tim

Tim — Tue, 24 Nov 2009 12:29:19 +0000

Hi John, Itokawa’s comment and your response got me wondering. Could you use the transfer pump to temporarily increase the tank pressure, and pass the pressure rise downstream to give an increased chamber pressure, and using the resultant increased performance to both reduce propellant consumption during refueling and increase the refueling window? You’d be trading a low pressure rise high flow pump for a high pressure rise low flow pump, and I’m not sure that makes sense. I suspect there is a flaw in my logic here, but I’m not sure where it is.

By: john hare

john hare — Mon, 23 Nov 2009 10:05:41 +0000

You don’t need a parachute Doug, just learn to fly, the rest of your life to learn.

By: Doug Jones

Doug Jones — Mon, 23 Nov 2009 05:42:34 +0000

A lot of these ideas- Rick’s “jack up the payload and insert a two stage rcoket” in particular- remind me of going skydiving without a parachute, you just grab one from your buddy after you go out the door. Yeah, you can make it work, but the failure modes are ugly…

By: john hare

john hare — Sat, 21 Nov 2009 16:52:31 +0000

A weird thought on suborbital refueling. Aries with no upper stage carries a honking big propellant tank. After SRB termination, an Atlas heavy refuels for a massive payload boost. Keeps everybody employed too.

By: Bob Steinke

Bob Steinke — Sat, 21 Nov 2009 00:12:13 +0000

When people say “why don’t you just build a bigger rocket” remind them of the Panama canal and supertankers. No matter how big you build it someone will come along the next day and ask for a little bigger.

By: nick

nick — Fri, 20 Nov 2009 22:07:01 +0000

Intriguing idea. Here’s a much simpler version:

(1) launch two rockets from two White Knight 2s, as before, but the first is a one-stage rocket carrying payload, shroud, and optional orbital transfer stages, and the second is a two-stage rocket;
then
(2) jettison the consumed first stage from the first rocket, leaving the payload/shroud/etc.;
meanwhile
(3) jettison the consumed first stage from the second rocket;
then
(4) dock the second stage of the second rocket with the payload/shroud.

No worry about fuel lines, pumps, pumping rates, etc.

By: Pete

Pete — Fri, 20 Nov 2009 21:59:46 +0000

“I’m not positive, but I don’t think the scaling works out like that. I don’t think you can deliver a single person to orbit on a vehicle launched off of a WK2.”

Then the first and foremost design challenge is to “make” the scaling work out like that. The alternative is billion dollar development programs that forget where they are before they even get one prototype built. Is not fifty years of such boondoggles enough?

There is an awful lot to be learned, many prototypes are yet required. Assuming ~$300 million overall funding maybe $10 million dollar prototypes that take six months are possible without people losing their way. Simply throwing more money at this problem has specifically not solved it countless times in the past.

$3 million prototypes would seem to be a lot safer scale, especially to start with (plan on vehicle growth). How large a reusable rocket vehicle might you prototype for $3 million? At $10,000 a kilogram of dry mass I get maybe 50-100kg of payload (very low dry mass fractions and reentry systems will be required). Maybe 5 ton air launched GLOW – well within WK2′s capability.

Five years before you have to start paying the investment back (definitely no more than ten). Ten prototypes in five years means one on average every six months, and the last few prototypes will probably have to enter service. Skimping on prototype number would probably not be a good idea.

So what technologies and development tricks (like sub orbital stepping stones), are necessary to develop orbital launch vehicles at these individual prototype cost/time scales? How much might the prototype cost/time, and hence overall development cost/time be reduced?

By: kert

kert — Fri, 20 Nov 2009 18:00:30 +0000

That reminds me of the Single Stage to Tether concept, where a subrobital would be helped to orbit by a rotating orbital tether.
see spacetethers.com