**** Elon Says

**** Elon Says (transcripts)
http://****elonsays.com/transcript

There are some interesting nuggets of information in the September 29
2013 transcript.

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

In article ,
says...

"Jeff Findley" wrote in message
...
**** Elon Says (transcripts)
http://****elonsays.com/transcript

There are some interesting nuggets of information in the September 29
2013 transcript.

An amusing site to maintain an archive of Elon's musings, but what do you
think are the most interesting statements in this last press conference?

I found all the info on reusability of the first stage(s) interesting.
For example:

[Question on performance hit for attempting landing the first stage]
We effectively lose, in terms of performance... It really depends on
what we want to do with the stage if we were to do an ocean landing
or a return to launch site landing. If we do an ocean landing, the
performance hit is actually quite small at maybe in the order of
15%. If we do a return to launch site landing, it's probably double
that, it's more like a 30% hit (i.e., 30% of payload lost).

[Question on the recovery of the first stage during CRS flights]
Our goal is to recover the first stage on all CRS flights and
really on most flights. The next two flights are somewhat of an
exception. When we negotiated these deals, we didn't have much
bargaining power. It was before we obviously flown this version
of the Falcon 9 successfully. So we kind of agreed to give up
all performance on the rocket and not reserve anything for
reusability. But going into the future, with future contracts,
with a few exceptions, we have reserved enough performance to
recover the stage. It's not just the CRS flights, it should be
most flights after these next two (flights). In terms when we
actually re-fly the stage, it's going to depend on what
condition the stage is in and obviously getting customers
comfortable with that. So it's difficult to say when would
actually re-fly it. If things go super well then we would be
able to re-fly a Falcon 9 stage before the end of next year
and that's our aspiration.

[Question on the impact of this version of Falcon 9 on the
Falcon Heavy] It (i.e. the Falcon 9 version 1.1) definitely
informs the Heavy development. The Falcon Heavy is essentially
the Falcon 9 with two additional boost stages as strap on
boosters. So it's the same engines that we use, very similar
airframe, the airframe will be slightly optimized because of
the fact that it is a side booster but the avionics will be
the same as the Falcon 9 first stage. How we control the whole
thing will be very very similar. Hopefully, once the three
boost stages separate, they will come back and land
individually and they will behave just like the Falcon 9 boost
stage. All three of them will come back hopefully and land on
three separate pads and we'll join them back together for a
future flight and launch them.

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

On 10/8/2013 11:02 AM, Jeff Findley wrote:
I found all the info on reusability of the first stage(s) interesting.
For example:

[Question on performance hit for attempting landing the first stage]
We effectively lose, in terms of performance... It really depends on
what we want to do with the stage if we were to do an ocean landing
or a return to launch site landing. If we do an ocean landing, the
performance hit is actually quite small at maybe in the order of
15%. If we do a return to launch site landing, it's probably double
that, it's more like a 30% hit (i.e., 30% of payload lost).


On this point I'm wondering how much of that 30% figure is due to the
trajectory the first stage would have to fly for a RTLS landing. Would
that figure be better if there was a "dry-land" or "sea-barge" option
further down the flight path? One that would allow the booster to follow
the more traditional "ballistic" trajectory? And if so, how much (as a
percentage of payload lost) would that regain? Of course at the cost of
having to transport the first stage back to the launch site. But it
might be a trade-off worth having...

Dave

David Spain wrote:
On 10/8/2013 11:02 AM, Jeff Findley wrote:
I found all the info on reusability of the first stage(s) interesting.
For example:

[Question on performance hit for attempting landing the first stage]
We effectively lose, in terms of performance... It really depends on
what we want to do with the stage if we were to do an ocean landing
or a return to launch site landing. If we do an ocean landing, the
performance hit is actually quite small at maybe in the order of
15%. If we do a return to launch site landing, it's probably double
that, it's more like a 30% hit (i.e., 30% of payload lost).


On this point I'm wondering how much of that 30% figure is due to the
trajectory the first stage would have to fly for a RTLS landing. Would
that figure be better if there was a "dry-land" or "sea-barge" option

I was assuming "ocean landing" was really "sea-barge" - does one
really want to be soaking a booster one expects to re-use in salt
water? Of course, I suspect that means *three* sea-barges for an F9H,
probably each some reasonable distance apart because you don't want a
fubar with one arriving booster taking-out the other two.

rick jones

further down the flight path? One that would allow the booster to follow
the more traditional "ballistic" trajectory? And if so, how much (as a
percentage of payload lost) would that regain? Of course at the cost of
having to transport the first stage back to the launch site. But it
might be a trade-off worth having...

Dave



--
firebug n, the idiot who tosses a lit cigarette out his car window
these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

In message
Rick Jones wrote:

I was assuming "ocean landing" was really "sea-barge" - does one
really want to be soaking a booster one expects to re-use in salt
water? Of course, I suspect that means *three* sea-barges for an F9H,
probably each some reasonable distance apart because you don't want a
fubar with one arriving booster taking-out the other two.

That's what I'd understood as well. The platform for the core stage will
be further down range than the ones for the side boosters anyway, and
you might be able to get away with a single long platform with some
superstructure acting as a blast shield between two pads as the stages
ought to be running on fumes by then. It will probably come down to
running costs for two platforms compared to replacement cost of an
occasional first stage.

Anthony

In article , nospam@
127.0.0.1 says...

On 10/8/2013 11:02 AM, Jeff Findley wrote:
I found all the info on reusability of the first stage(s) interesting.
For example:

[Question on performance hit for attempting landing the first stage]
We effectively lose, in terms of performance... It really depends on
what we want to do with the stage if we were to do an ocean landing
or a return to launch site landing. If we do an ocean landing, the
performance hit is actually quite small at maybe in the order of
15%. If we do a return to launch site landing, it's probably double
that, it's more like a 30% hit (i.e., 30% of payload lost).


On this point I'm wondering how much of that 30% figure is due to the
trajectory the first stage would have to fly for a RTLS landing.

The quote seems quite clear. The performance hit is 15% for an ocean
"landing" and 30% for a RTLS landing.

Would
that figure be better if there was a "dry-land" or "sea-barge" option
further down the flight path? One that would allow the booster to follow
the more traditional "ballistic" trajectory? And if so, how much (as a
percentage of payload lost) would that regain? Of course at the cost of
having to transport the first stage back to the launch site. But it
might be a trade-off worth having...

Doubtful in my mind since fuel costs are still quite low compared to
launch costs. You snipped the quote about reusable Falcon Heavy first
stages, but if more performance is needed, three first stages will be
better than one.

Recovering flown first stages pays double dividends. You can reuse the
stage if it's recovered in good condition. However, if it's not
recovered in good condition, recovering it allows you to determine
exactly what went wrong so any necessary design changes can be made.

Conversely, by choosing to continue dumping expended stages in the
ocean, you pay a double hit. By not recovering stages in good shape,
you're throwing away perfectly good, expensive, hardware on each and
every flight. By not recovering stages which aren't in good shape,
you're completely missing the opportunity to do a detailed analysis of
what went wrong. Even worse, by not recovering and at least inspecting
flown stages, how would you know "good" from "bad"? A stage could be a
hair's width from failure, and you might never even know it from the
(limited) telemetry available during launch.

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

In article ,
says...

David Spain wrote:
On this point I'm wondering how much of that 30% figure is due to the
trajectory the first stage would have to fly for a RTLS landing. Would
that figure be better if there was a "dry-land" or "sea-barge" option

I was assuming "ocean landing" was really "sea-barge" - does one
really want to be soaking a booster one expects to re-use in salt
water? Of course, I suspect that means *three* sea-barges for an F9H,
probably each some reasonable distance apart because you don't want a
fubar with one arriving booster taking-out the other two.

I'd say you don't want to submerge expensive aerospace grade hardware in
salt water. For most common aerospace materials, this would not be a
good thing.

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

In article , says...

In message
Rick Jones wrote:
I was assuming "ocean landing" was really "sea-barge" - does one
really want to be soaking a booster one expects to re-use in salt
water? Of course, I suspect that means *three* sea-barges for an F9H,
probably each some reasonable distance apart because you don't want a
fubar with one arriving booster taking-out the other two.

That's what I'd understood as well. The platform for the core stage will
be further down range than the ones for the side boosters anyway, and
you might be able to get away with a single long platform with some
superstructure acting as a blast shield between two pads as the stages
ought to be running on fumes by then. It will probably come down to
running costs for two platforms compared to replacement cost of an
occasional first stage.

You'd have to do a detailed analysis to find out what is cheaper in the
long run. But I'm guessing that comparing the relatively low fuel costs
for flying the stages back versus the cost of building, operating, and
maintaining such a mobile ocean going landing platform is going to yield
a very clear answer.

The trade here is performance versus cost. Elon is hyper focused on
cost. If a customer demands higher performance, they can always pay the
higher cost of expending the Heavy's center core rather than recovering
it. If the customer really wants to spend some money, they could pay
for all stages to be expended. But in that case, why bother with Falcon
Heavy in the first place? Why not fly on a Delta IV Heavy instead?

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

On Wed, 9 Oct 2013 07:45:59 -0400, Jeff Findley
wrote:

In article , says...

In message
Rick Jones wrote:
I was assuming "ocean landing" was really "sea-barge" - does one
really want to be soaking a booster one expects to re-use in salt
water? Of course, I suspect that means *three* sea-barges for an F9H,
probably each some reasonable distance apart because you don't want a
fubar with one arriving booster taking-out the other two.

That's what I'd understood as well. The platform for the core stage will
be further down range than the ones for the side boosters anyway, and
you might be able to get away with a single long platform with some
superstructure acting as a blast shield between two pads as the stages
ought to be running on fumes by then. It will probably come down to
running costs for two platforms compared to replacement cost of an
occasional first stage.

You'd have to do a detailed analysis to find out what is cheaper in the
long run. But I'm guessing that comparing the relatively low fuel costs
for flying the stages back versus the cost of building, operating, and
maintaining such a mobile ocean going landing platform is going to yield
a very clear answer.

I would think fuel cost is in the noise compared to say the cost of
refurbishing components touched by salt water.

think out of the box, just before water impact, perhaps a parachute deploys, and some transhab bags inflate to keep most of the booster from being submerged..

of course the booster could be built with salt water resistant materials.