Stratolaunch & Sierra Nevada Pact Would Put Commercial AstronautsBack On Solids?

I believe I've read elsewhere that the only Orbital Sciences rocket powerful enough to put the Dream Chaser into orbit is a solid rocket with liquid rocket insertion motor as a 2nd stage (3rd if you count the Stratolaunch aircraft as a first stage)? Is this correct?

Does Orbital Sciences have any plans on the drawing board for a liquid-only upper stage powerful enough to put the Dream Chaser into orbit?

Dave

In article ,
says...

I believe I've read elsewhere that the only Orbital Sciences rocket powerful enough to put the Dream Chaser into orbit is a solid rocket with liquid rocket insertion motor as a 2nd stage (3rd if you count the Stratolaunch aircraft as a first stage)? Is this correct?

Does Orbital Sciences have any plans on the drawing board for a liquid-only upper stage powerful enough to put the Dream Chaser into orbit?

Dave

The Stratolaunch website isn't very forthcoming with details, but it
does say:

Orbital will be responsible for the program's overall systems
engineering, as well as the development, production, integration,
test, and operations of the air launch vehicle and related
support systems.

In other words, we're not going to learn anything unless Orbital and
Stratolaunch want us to know.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

Some background...

http://www.nasaspaceflight.com/2014/...launch-system/

In article ,
says...

Some background...

http://www.nasaspaceflight.com/2014/...launch-system/

Firstly, designing a 75% scale Dream Chaser sounds "easy" on the face of
it, but it won't be easy at all. Mass constraints and scaling laws mean
the whole thing will need to be redesigned, re-tested, and rebuilt. But
that's not even the scary part for me.

From above:

The first and second stages are made from "carbon-composite wound"
cases, with the same outside diameter as the Shuttle Solid Rocket
Booster (SRB) segments.

These two stages will sport additional performance via an updated
propellant mix, under development by ATK, who are working to
complete a merger with Orbital.

snip

The first two stages will act like a single first stage, given
they will provide half of the required Delta-v. However,
information notes the first stage may also be recoverable after
staging and splashdown.

snip

However, the review into the rocket system is understood to be
looking at an all-solid version of the rocket.

snip

Meanwhile, ATK has been asked to evaluate and price a two stage
replacement for the liquid upper stage, believed to be a
Castor 30 combo (XL and/or B).

So, this is shaping up to be an ATK/Orbital all solids launcher, *if*
ATK can eek out the performance needed. Upper stages are usually very
performance critical and tossing out a LOX/hydrogen stage and replacing
it with two additional solid stages would seem to be a bit risky from a
systems engineering point of view. Those two stages will likely be
heavier than the single LOX/hydrogen stage they replace. If so, what
part of the system will be forced to lose mass to make up for the
shortfall?

Even if successful, this would be a 5 stage vehicle. First stage being
the carrier aircraft followed by four solid stages. My fear, as an
engineer, is that the delta-V "error bars" caused by four solid stages
could result in an increased delta-V requirement for the 75% scale Dream
Chaser in order to make up for any total delta-V shortfalls or overages
in the solid stages. Unless I am mistaken, it's been a long time since
ATK worked on composite wound solids that large.

But, for me, this whole thing would be a non-starter. I'd consider the
first two stages to be "large solids" based on the fact that the "first
and second stages are made from 'carbon-composite wound' cases, with the
same outside diameter as the Shuttle Solid Rocket Booster (SRB)
segments".

I would "just say no" to large solid rocket motors (boosters) on manned
spacecraft. They may be cheaper to develop, but the long term
repercussions of their demonstrated failure modes means people will
surely die.

In conclusion, SNC entering into partnership with Orbital/ATK to put
people on top of large solids looks to me like a "deal with the devil".
An all solid launcher was *not* their first choice. This looks like a
desperate final attempt to snatch victory from the jaws of defeat.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

No argument. The whole idea of Orbital moving away from Aerojet towards more ATK stages would certainly NOT be my first choice for a booster for a scaled Dream Chaser.

Thanks Jeff for the comments. It made me go back and read the article more carefully. Upon 2nd read and reflection, this seems like more desperation than inspiration. I don't see where the money comes from for a scaled Dream Chaser, unless (as I said before) its DARPA/USAF. Large cross-range options and launch anywhere, anytime makes much more sense for military ops than commercial ops.

Downscaling the Dream Chaser probably also compromises it's ability to remain in-orbit for any length of time as well as the kinds of useful payload it could take into orbit. Not directions the USAF would like to see.

A more economical upper stage for Stratolaunch does makes sense and I can understand that momentum given Stratolaunch is focusing primarily on uncrewed payload to orbit.