SuperDraco's Also Key to Falcon 9 Reuse?

SpaceX article on the SuperDraco engine which is planned for Dragon LES and
powered landing system might also be a key component in making the Falcon 9
first stage fully reusable.

http://www.spacex.com/updates.php

If Falcon 9's engine module were to be made separable from the tankage an
array of SuperDraco could be used to provide powered (& throttle-able) decent
capability to the engine module. I would assume the weight profile of the
engine module (less that 1st stage tankage) would be favorable (less than?)
compared to the Dragon capsule itself. This could provide the key technology
for getting those Merlins recovered on land. The tankage would float and could
come down separately via parachute for recovery at sea, where seawater
mitigation is likely more easily dealt with.

In an ideal set-up once the Merlins have been recovered they could be serviced
quickly, the SuperDracos refueled and then the engine module is re-mated to
another awaiting tank stage for quick assembly. Essentially gas-n-go.

Depending upon the cross-range of the SuperDraco powered engine module the
flight profile of the 1st stage would have to be modified to accommodate if it
were to be made fully reusable.

Even so, this seems to me far more practical and achievable than the
'lawn-dart' approach of trying to bring the 1st stage down all in one piece.

Dave

David Spain was thinking very hard :
SpaceX article on the SuperDraco engine which is planned for Dragon LES and
powered landing system might also be a key component in making the Falcon 9
first stage fully reusable.

http://www.spacex.com/updates.php

If Falcon 9's engine module were to be made separable from the tankage an
array of SuperDraco could be used to provide powered (& throttle-able) decent
capability to the engine module.

The RTLS video on that page shows an intact first stage returning to
the launch site, and an intact 2nd stage.

/dps

The whole issue of reuse of engines though, seems to be more of a problem
than one might think. The SMEs needed a lot of work done to validate them,
and I just wonder if they have factored the cost of this in sufficiently.
Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"Snidely" wrote in message
news:mn.dc667dc281a6d511.127094@snitoo...
David Spain was thinking very hard :
SpaceX article on the SuperDraco engine which is planned for Dragon LES
and powered landing system might also be a key component in making the
Falcon 9 first stage fully reusable.

http://www.spacex.com/updates.php

If Falcon 9's engine module were to be made separable from the tankage an
array of SuperDraco could be used to provide powered (& throttle-able)
decent capability to the engine module.

The RTLS video on that page shows an intact first stage returning to the
launch site, and an intact 2nd stage.

/dps

Brian Gaff brought next idea :
The whole issue of reuse of engines though, seems to be more of a problem
than one might think. The SMEs needed a lot of work done to validate them,
and I just wonder if they have factored the cost of this in sufficiently.
Brian

The SSMEs are more complicated than most rocket engines, aren't they?
And even with that, the 'tween-flight work was considerably reduced by
the time of the 2nd return-to-flight. (Actually, well before then, but
I don't have those flight numbers memorized.)

The SpaceEx engines are supposed to be one of the simpler designs,
aren't they?

/dps

In article , nospam@
127.0.0.1 says...

SpaceX article on the SuperDraco engine which is planned for Dragon LES and
powered landing system might also be a key component in making the Falcon 9
first stage fully reusable.

http://www.spacex.com/updates.php

If Falcon 9's engine module were to be made separable from the tankage an
array of SuperDraco could be used to provide powered (& throttle-able) decent
capability to the engine module. I would assume the weight profile of the
engine module (less that 1st stage tankage) would be favorable (less than?)
compared to the Dragon capsule itself. This could provide the key technology
for getting those Merlins recovered on land. The tankage would float and could
come down separately via parachute for recovery at sea, where seawater
mitigation is likely more easily dealt with.

You'd want to recover both the tanks and the engines. Keeping the
"fluffy", mostly empty, tanks means that heat loads on reentry are more
manageable. Plus if you make them separable, you need additional
hardware to do the separation, increasing complexity which tends to
drive up costs and drive down reliability.

In an ideal set-up once the Merlins have been recovered they could be serviced
quickly, the SuperDracos refueled and then the engine module is re-mated to
another awaiting tank stage for quick assembly. Essentially gas-n-go.

Depending upon the cross-range of the SuperDraco powered engine module the
flight profile of the 1st stage would have to be modified to accommodate if it
were to be made fully reusable.

Even so, this seems to me far more practical and achievable than the
'lawn-dart' approach of trying to bring the 1st stage down all in one piece.

Fully reusable systems can be fully flight tested before putting a
payload on top. Partially reusable systems can't, so you're always
going to be trusting payloads to fly on new, unflown, copies of
hardware.

Jeff
--
" Ares 1 is a prime example of the fact that NASA just can't get it
up anymore... and when they can, it doesn't stay up long. "
- tinker

In article ,
says...

The whole issue of reuse of engines though, seems to be more of a problem
than one might think. The SMEs needed a lot of work done to validate them,
and I just wonder if they have factored the cost of this in sufficiently.

SSME's are a single data point in terms of reusability. Please note
that compared to other (traditionally expendable) engines, the SSME is
an extreme case in terms of metrics like chamber pressure, ISP, and
engine cycle (staged combustion). When you consider the operating
conditions of the SSME, it's really no surprise that such a "high
strung" engine had problems.

SpaceX's Merlin engines are not especially high performance. I'd go so
far to say that they're average LOX/kerosene engines (the Russians have
cornered the market on those). Since Merlins are not pushing the edge
of the performance envelope, reusability ought to come far cheaper than
for the SSME.

Jeff
--
" Ares 1 is a prime example of the fact that NASA just can't get it
up anymore... and when they can, it doesn't stay up long. "
- tinker

Jeff Findley wrote:
You'd want to recover both the tanks and the engines. Keeping the
"fluffy", mostly empty, tanks means that heat loads on reentry are more
manageable.

I agree. However, it's seems really unclear what the flight profile of a fully
reusable Falcon 9 would be. If the 1st stage cross range capability is low,
I've read that the Falcon 9 1st stage takes a nearly vertical trajectory with
a corresponding sacrifice in payload capacity. The 'video' is really hazy on
this point. I would think any significant downrange distance and you're not
talking about return to launch point recovery anymore.

Plus if you make them separable, you need additional
hardware to do the separation, increasing complexity which tends to
drive up costs and drive down reliability.

There will have to be additional hardware in any case if F9 is to be made
reusable. So the question is not increasing complexity (there will be) but
managed complexity. For instance the SpaceX video shows landing gear being
deployed from the first stage. That won't be easy. Might be easier to make
that engine module nearly 'hover' on the SuperDracos and at a fixed height
safely drop the whole thing onto an airbag for instance.

I guess I have a really hard time imagining the aerodynamics of a controlled
return of a partially fueled first stage all in one piece. There is a lot of
surface area there, largely limited in its ability to control the rocket
aerodynamically and relying largely on the center rank Merlins for stability
and control. Then there is the issue of fluids sloshing around in free
floating returning tankage. All this coming down at tremendous speed (the
faster the return the more stable that whole stack will be). That's asking a
lot of a control system. Why not take a chapter from the Scaled Composites
play-book and play up your strengths? Re-use whatever you can for the purposes
it was designed for. In this case the SuperDraco is intended to perform this
very function for Dragon, why not F9?

Fully reusable systems can be fully flight tested before putting a
payload on top. Partially reusable systems can't, so you're always
going to be trusting payloads to fly on new, unflown, copies of
hardware.

Jeff

-*- On the business of expendable vs reusable -*-

Yes I agree. Where we might disagree somewhat is over the tone of your
statement. It sounds like you are implying that the risk always outweighs the
other benefits of expendable hardware (such as cost). There is a higher degree
of risk on expendable hardware but it can be or should be a mitigated risk.
Based on my experiences with manufactured electronics, if the specifications
are rigorous, adhere well within vendor's tolerances and margins and designed
with ease of manufacture in mind (ease of assembly, repeatability of assembly,
& limited number of manual steps required) even untried hardware will yield
few surprises. Every electronic assembly is essentially 'unflown' when first
powered on. Although the consequences of failure aren't usually as dramatic as
a rocket failure. Tantalum capacitors notwithstanding... ;-)

However, to skip ahead a few steps, I think what you are really driving at is
that as you gain experience with hardware that is reusable you can greatly
improve its reliability. More so than with expendable hardware. I think you
probably have or can find a great wealth of data from the airline industry to
back this claim up. Of that I have no doubt. When the flight rates of the
space business get to those that approach the airline business this will
likely be the better approach. But even with expendable hardware, if the
design is weighted towards producing highly repeatable, exacting duplication,
and the manufacturing processes are under good control, the question is more
of being able to identify the problem rather than worry that the fix won't
work. That's an issue of telemetry or data capture, and for that matter that
is a problem for both re-usable and non re-usable hardware.

-*- Regarding why SpaceX wishes to pursue re-usable hardware? -*-

I think it seems that what is driving SpaceX towards re-usability is cost not
risk. I don't think you disagree with this.

Dave

In article mn.e03c7dc2f59dd83e.127094@snitoo,
says...

Brian Gaff brought next idea :
The whole issue of reuse of engines though, seems to be more of a problem
than one might think. The SMEs needed a lot of work done to validate them,
and I just wonder if they have factored the cost of this in sufficiently.
Brian

The SSMEs are more complicated than most rocket engines, aren't they?
And even with that, the 'tween-flight work was considerably reduced by
the time of the 2nd return-to-flight. (Actually, well before then, but
I don't have those flight numbers memorized.)

Yes. SSME's are high chamber pressure, high ISP, staged combustion,
LOX/LH2 engines. They're arguably the most exotic, routinely flown,
liquid fueled rocket engine in US spaceflight history.

The SpaceEx engines are supposed to be one of the simpler designs,
aren't they?

Yes. They're LOX/kerosene engines that do not push the envelope in
terms of performance. If you want LOX/kerosene engines that are higher
performance, you can buy them from the Russians like the US does for
Atlas V's first stage.

Jeff
--
" Ares 1 is a prime example of the fact that NASA just can't get it
up anymore... and when they can, it doesn't stay up long. "
- tinker

Snidely wrote:
David Spain was thinking very hard :
If Falcon 9's engine module were to be made separable from the tankage
an array of SuperDraco could be used to provide powered (&
throttle-able) decent capability to the engine module.

The RTLS video on that page shows an intact first stage returning to the
launch site, and an intact 2nd stage.

/dps

Yes I've seen that video. I just have a hard time believing it.
Intact 1st stage that is. The intact 2nd stage is very interesting, requiring
a bit of flight acrobatics to go engine first, then heat shield first, then
back again to engine first. Not impossible, just complex.

Also, what makes me skeptical of these RTLS scenarios is whether they require
flight of hardware over populated areas (depending upon the LS). With little
or no prior flight experience to draw from that seems also highly unlikely to
garner FAA approval. More likely you have recovery taking place in the open
ocean, for "landers" that could be the level surface of a sea barge, but well
enough out to sea to not present a ground hazard. Also if launching from KSC
or Vandenburg, etc. it gives you the ability to go downrange with the 1st
stage, which increases payload.

As you gain experience with the systems then maybe you can get FAA approvals
to come in closer to the LS, which is the cost savings.

I'm curious, it does beg the question. What are the FAA reqs. concerning the
flight of UAVs in US airspace? That's essentially what these pieces are...

Dave

In article , nospam@
127.0.0.1 says...

Snidely wrote:
David Spain was thinking very hard :
If Falcon 9's engine module were to be made separable from the tankage
an array of SuperDraco could be used to provide powered (&
throttle-able) decent capability to the engine module.

The RTLS video on that page shows an intact first stage returning to the
launch site, and an intact 2nd stage.

/dps

Yes I've seen that video. I just have a hard time believing it.
Intact 1st stage that is. The intact 2nd stage is very interesting, requiring
a bit of flight acrobatics to go engine first, then heat shield first, then
back again to engine first. Not impossible, just complex.

Also, what makes me skeptical of these RTLS scenarios is whether they require
flight of hardware over populated areas (depending upon the LS). With little
or no prior flight experience to draw from that seems also highly unlikely to
garner FAA approval. More likely you have recovery taking place in the open
ocean, for "landers" that could be the level surface of a sea barge, but well
enough out to sea to not present a ground hazard. Also if launching from KSC
or Vandenburg, etc. it gives you the ability to go downrange with the 1st
stage, which increases payload.

As you gain experience with the systems then maybe you can get FAA approvals
to come in closer to the LS, which is the cost savings.

I'm curious, it does beg the question. What are the FAA reqs. concerning the
flight of UAVs in US airspace? That's essentially what these pieces are...

From what I understand, reusable launch vehicles are being treated a bit
different than aircraft. The guys on ARocket know the gory details
because they're actually fling small, reusable, VTVL liquid fueled
vehicles for quite some time. SpaceX is definitely scaling things up,
but I don't see anything they're trying that's completely unproven.

Jeff
--
" Ares 1 is a prime example of the fact that NASA just can't get it
up anymore... and when they can, it doesn't stay up long. "
- tinker