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Space X 2nd stage recovery



 
 
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  #11  
Old April 20th 18, 02:23 PM posted to sci.space.policy
David Spain
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Default Space X 2nd stage recovery

On 4/19/2018 6:26 PM, Fred J. McCall wrote:
JF Mezei wrote on Thu, 19 Apr 2018
18:07:43 -0400:

On 2018-04-19 16:20, David Spain wrote:

Yes I agree. I suspect they are using it mainly for learning curve
rather than practical economics, with BFR looming.


Could balloons be used for landing cargo on Mars? (yeah, they would need
to be huge ballons due to low atmosphere pressure).


Only part way. You could use a balloon (or ballute) to increase cross
sectional area to increase drag for aerobraking, but you're not going
to actually get enough lift to land anything that way. There was a
'balloon/bouncy house' solution where the balloon(s) expanded around
the payload which then aerobraked and was simply allowed to strike the
surface. This only works for light payloads and I don't know if they
ever tried it.



Fred this was tried at least once I can remember. The first Mars rovers
(Spirit & Opportunity) were light enough that inflated balloons where
used to bounce land them on the surface of Mars after parachute.

The follow-on rover Curiosity was too heavy for that approach and used
the sky-crane retro-rocket approach after parachute.

Dave

  #12  
Old April 23rd 18, 12:37 AM posted to sci.space.policy
Greg \(Strider\) Moore
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Default Space X 2nd stage recovery

"Jeff Findley" wrote in message
...

In article ,
says...

"JF Mezei" wrote in message news

On 2018-04-17 20:05, Jeff Findley wrote:
In article ,
says...

https://www.space.com/40313-spacex-r...y-balloon.html

By "party balloon" are we talking helium or Hydrogen filled balloons
that will "lift" the stage to slow its descent? (and I assume provide
drag initially).


I'm guessing nitrogen myself. I don't think lift is nearly as important
at
this point is as drag over as large a surface area as you can manage.


I heard helium, because while lift isn't important, mass most certainly
is. And at the same volume and pressure, helium masses less than
nitrogen. The mass of the molecule doesn't enter into the ideal gas
law:

P*V = N*R*T

Jeff

Fair point. And I believe they already have helium tanks on board, just use
those as part of the supply.

  #13  
Old April 23rd 18, 11:05 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Default Space X 2nd stage recovery

JF Mezei wrote on Mon, 23 Apr 2018
14:20:01 -0400:

On 2018-04-22 19:37, Greg (Strider) Moore wrote:

Fair point. And I believe they already have helium tanks on board, just use
those as part of the supply.


In terms of mass, wouldn't the mass of the balloon(s) be far more
significant than that of the gas used to fill it/them?


That depends on whether it's intended to just be a big, draggy bag or
they're going to try to do something like a paraglider ballute.


How heavy would the fabric need to be to survive re-entry?


Again, it rather depends on just how they plan to do it, which we
don't know.


Or would they go with lighter "disposable" material where on balloon
does initial slowing down before re-entry interface (where it burns up)
and after it, another baloon is deployed do to the drag/lift in denser
atmosphere?


Go read the original article again. That's one thing we know they are
NOT doing from what Musk said.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw
  #14  
Old April 24th 18, 12:10 PM posted to sci.space.policy
Jeff Findley[_6_]
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Default Space X 2nd stage recovery

In article ,
says...

"Jeff Findley" wrote in message
...

I heard helium, because while lift isn't important, mass most certainly
is. And at the same volume and pressure, helium masses less than
nitrogen. The mass of the molecule doesn't enter into the ideal gas
law:

P*V = N*R*T

Jeff

Fair point. And I believe they already have helium tanks on board, just use
those as part of the supply.


They do, to pressurize the kerosene and LOX tanks for the Merlin engine.
Adding another gas would complicate pad operations (only a bit, but
still).

I'm glad they're working on upper stage recovery. My guess is that
BFR/BFS will take a bit longer than Elon's aspirational schedule
products. As such, Falcon 9 and Falcon Heavy will remain the workhorses
of SpaceX for many years to come. Anything they can do to cut their
costs increases the cash they can funnel into BFR/BFS development.

Same goes for Starlink. That needs to be developed, built, and launched
quickly in quantity for them to maintain the number of satellites that
goes with their FCC agreement. That's a "use it or lose it" type of
thing. You can't apply for and be granted bandwidth and just "sit on
it". You have to use it. Improving Falcon 9 and Falcon Heavy reuse
will help keep costs down for launching Starlink as well.

Jeff
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  #15  
Old April 24th 18, 12:16 PM posted to sci.space.policy
Jeff Findley[_6_]
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Default Space X 2nd stage recovery

In article ,
says...

On 2018-04-22 19:37, Greg (Strider) Moore wrote:

Fair point. And I believe they already have helium tanks on board, just use
those as part of the supply.


In terms of mass, wouldn't the mass of the balloon(s) be far more
significant than that of the gas used to fill it/them?


Depends on the details. But in general I'd say the mass of the gas is
quite significant because every kg added to the upper stage for reuse
reduces payload capacity by the same amount.

How heavy would the fabric need to be to survive re-entry?


Depends on the details. Build a little, test a little, fly a little.

Or would they go with lighter "disposable" material where on balloon
does initial slowing down before re-entry interface (where it burns up)
and after it, another baloon is deployed do to the drag/lift in denser
atmosphere?


Depends on the details, but in general SpaceX has tried to reuse as much
as they can. They don't even use "pyros" to do stage separation. They
use pneumatic cylinders instead. Even the landing gear on Block 5 will
be retractable (earlier versions locked in place and had to be removed
from the stage so it could be transported). Designing everything for
reuse allows for higher flight rates.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #16  
Old April 24th 18, 07:21 PM posted to sci.space.policy
David Spain
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Default Space X 2nd stage recovery

On 4/24/2018 7:10 AM, Jeff Findley wrote:
I'm glad they're working on upper stage recovery. My guess is that
BFR/BFS will take a bit longer than Elon's aspirational schedule
products. As such, Falcon 9 and Falcon Heavy will remain the workhorses
of SpaceX for many years to come. Anything they can do to cut their
costs increases the cash they can funnel into BFR/BFS development.

I am of the opinion that the existing F9 and F9H architectures will be
(crew-wise) underutilized. In a perfect world, a "white knight" would
step forward and say, "Look we love what you have flying already. And we
want to build our own (crewed) space program around it." That WK *could*
be NASA, but thanks to politics (and SLS) its likely going to have have
to be either business, academia or another country. Politics makes all
things complicated. But if an ally (like Australia) came forward, esp.
if they not only came with a checkbook but with a request for contract
to have SpaceX build an Australian launch complex with them....

But let's see what Bridenstein can pull off.


Same goes for Starlink. That needs to be developed, built, and launched
quickly in quantity for them to maintain the number of satellites that
goes with their FCC agreement. That's a "use it or lose it" type of
thing. You can't apply for and be granted bandwidth and just "sit on
it". You have to use it. Improving Falcon 9 and Falcon Heavy reuse
will help keep costs down for launching Starlink as well.


All good.
  #17  
Old April 24th 18, 10:54 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Default Space X 2nd stage recovery

JF Mezei wrote on Tue, 24 Apr 2018
16:36:20 -0400:

On 2018-04-24 14:21, David Spain wrote:

I am of the opinion that the existing F9 and F9H architectures will be
(crew-wise) underutilized.


Unless the space station life is extended beyond 2025, FH and Dragon2
may very well remain the workhorse for mnanned space in USA.


So Boeing is irrelevant in your mind?


And unless there is real funding for manned space programme beyond ISS,
nobody will see much business case to invest in manned space programme
from now on, unless you go for it on your own (aka: SpaceX with BFR to
Mars).


The issue here is that Bigelow seems to have jumped in bed with ULA.
If that extends to ferrying supplies and 'guests' to 'space hotels',
they might not let SpaceX vehicles dock.


Where the "international" thing may fall in place is if SpaceX gets
serius about mars and other countries want "in" on the project,
supplying modules for the Mars colony or any other "help" they can
provide to SpaceX.


Or just people who want to go to Mars. If there are enough, it would
make sense to launch from almost anywhere.


But unless a place like Australia could provide a huge cost and
logistics benefit to have SpaceX launch/land there, SpaceX might not be
so interested when you consider transportation logistics for modules
built in USA.


Remember, BFR Spaceship can do point to point travel on Earth and land
anywhere there's a big enough piece of concrete.


In the case of a LEO assembly/refueling spot to later go to Mars, would
launching from 12°S (northern Australia) offer significant performance
advantage over 28°N (Canaveral)?


I don't think it buys you that much. BFR Spaceship is 'no assembly
required'. You just need to be able to launch fuel tankers to the
same orbital plane. They're going to be doing the manufacturing in
the LA area and then transporting to the original launch site by ship.
I think all the inspection and such will occur at the launch site.
That makes locating the facility outside the US something of an ITAR
issue. I wouldn't expect Australia to be a problem, but you never
know...


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw
  #18  
Old April 25th 18, 01:43 AM posted to sci.space.policy
Greg \(Strider\) Moore
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Posts: 752
Default Space X 2nd stage recovery

"JF Mezei" wrote in message ...

On 2018-04-24 07:10, Jeff Findley wrote:

I'm glad they're working on upper stage recovery. My guess is that
BFR/BFS will take a bit longer than Elon's aspirational schedule
products.



If SpaceX truly stops production of Merlin engine as it moves its
operatiosn to BFR/BFS, despite recovering stage 1s, won't they
eventually run out of engines for stage 2?


I suspect they'll keep building engines for awhile, simply to have enough
and to build in improvements.
But the rate will probably decrease.


or will SpaceX in reality continue to produce the engines at least for
the upper stage config ?

If they can recover stage 2 engines reliably, this could enable ending
production of the engines to retool for BFR/BFS ?


Eh, I'm not sure it's a huge problem.

--

  #19  
Old April 25th 18, 01:46 AM posted to sci.space.policy
Greg \(Strider\) Moore
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Default Space X 2nd stage recovery

"JF Mezei" wrote in message ...

On 2018-04-24 07:10, Jeff Findley wrote:

They do, to pressurize the kerosene and LOX tanks for the Merlin engine.
Adding another gas would complicate pad operations (only a bit, but
still).



Wouldn't that require running additional piping up the launch tower and
new connection points on the rocket to load the gas into the tanks,
along with the pipe unhooking hardware at launch time?


No you just use the existing piping and connection points.



Is that considered "major" or a no brainer type of work?


I think adding a few additional tanks is the least of the issues.

Ensuring proper inflation and then controlling the lift enough to navigate
is going to take the most work.

But again, it's sort of a no-brainer. For the flights that can take the hit
to the payload, you enable this option.

You test until it works and then make it operational. If you fail, you
haven't lost anything you haven't already written off.



  #20  
Old April 25th 18, 01:49 AM posted to sci.space.policy
Greg \(Strider\) Moore
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Posts: 752
Default Space X 2nd stage recovery

"Jeff Findley" wrote in message
...

In article ,
says...

"Jeff Findley" wrote in message
...

I heard helium, because while lift isn't important, mass most certainly
is. And at the same volume and pressure, helium masses less than
nitrogen. The mass of the molecule doesn't enter into the ideal gas
law:

P*V = N*R*T

Jeff

Fair point. And I believe they already have helium tanks on board, just
use
those as part of the supply.


They do, to pressurize the kerosene and LOX tanks for the Merlin engine.
Adding another gas would complicate pad operations (only a bit, but
still).


Yeah, only a 'bit' but still some. And SpaceX seems to be focused more on
the mantra of "simpler is better". They'd rather give up a hair of payload
in return for simplifying operations. And this is a welcome contrast to
performance uber alles.


I'm glad they're working on upper stage recovery. My guess is that
BFR/BFS will take a bit longer than Elon's aspirational schedule
products.


Agreed 100%. I never really believe his schedules until about 10 seconds to
lift-off :-)

As such, Falcon 9 and Falcon Heavy will remain the workhorses
of SpaceX for many years to come. Anything they can do to cut their
costs increases the cash they can funnel into BFR/BFS development.


Perhaps. On the other hand they're spending more money developing this.


Same goes for Starlink. That needs to be developed, built, and launched
quickly in quantity for them to maintain the number of satellites that
goes with their FCC agreement. That's a "use it or lose it" type of
thing. You can't apply for and be granted bandwidth and just "sit on
it". You have to use it. Improving Falcon 9 and Falcon Heavy reuse
will help keep costs down for launching Starlink as well.


Fair enough point.


Jeff


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