[AR] Re: SSTO
- From: Bill Bruner <bill@xxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sun, 11 Feb 2018 19:28:53 -0800
What’s the appeal of an SSTO over landing your multiple stages of
boosters? I’d think you’d get less payload to orbit for the same fuel, so
if you already solved re-use of the first stage.. what is it?
Let me respectfully suggest that "payload to orbit" is the wrong metric.
People who want to make money flying reusable rockets care about sortie
rates, turnaround costs and operational flexibility, not maximizing payload.
With SSTO, the operator doesn't need separate recovery forces for multiple
stages, doesn't have to transport separate stages back to the refurbishment
facility and doesn't have to re-integrate the stages before the next launch.
All of this saves time and money - which adds to the bottom line and is
worth the lost payload.
Bill Bruner
New Frontier Aerospace
bill@xxxxxxxxxx
925-456-4553
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On Sun, Feb 11, 2018 at 3:04 PM, Eivind Liland <spookysys@xxxxxxxxx> wrote:
What’s the appeal of an SSTO over landing your multiple stages of
boosters? I’d think you’d get less payload to orbit for the same fuel, so
if you already solved re-use of the first stage.. what is it?
11. feb. 2018 kl. 21:13 skrev Craig Fink <webegood@xxxxxxxxx>:
On Sat, Feb 10, 2018 at 2:46 PM, William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
Today, I would want to carefully understand two technologies: very low
power thrusting during entry to provide a stand-off gas blanket (and
specially the mass of propellant required)
I too have been thinking about this one for a while, and seems to me to be
the way to go. If done right, I would think the mass penalty would be
minimal. But first, the vacuum engine bell has an expansion ratio that is
too large to operate deep in the atmosphere, but it will run just fine
without it's nozzle extension.
One solution fits
https://i.stack.imgur.com/uKx53.jpg
So, the extension needs to be replaced with a variable nozzle extension
similar to a jet, but designed for a rocket and able to open much wider
(even reversing) for the heat shield mode. The weight of the much heavier
variable nozzle extension could be mitigated by removing the engine gimbals
and traditional TVC and using the variable nozzle extension for ascent,
entry and atmospheric flight TVC. Increasing the expansion ratio of the
variable nozzle increase ascent performance, while providing additional
"wake shielding" of the tanks. The second stage could then land on the
engine to nozzle extension joint, so landing gear would not be required.
The "stand-off gas blanket" or film cooling of the variable nozzle
extension would be minimal for parts that are all ready built from high
temperature materials. I would think this type of entry would favor a short
high gee entry of a longer lifting low gee entry. The CG of the second
stage is at or near the engine resulting in a dynamically stable entry and
atmospheric flight. Plus, assent, entry and landing forces are all in the
same direction, the structure was built to handle load in the +X direction.
--
Craig Fink
WeBeGood@xxxxxxxxx
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