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Space X 2nd stage recovery



 
 
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  #1  
Old April 17th 18, 08:19 PM posted to sci.space.policy
Greg \(Strider\) Moore
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Default Space X 2nd stage recovery

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

I find this interesting for a couple of reasons.

The approach is interesting and I wonder who much it'll impact the final
payload numbers.

But more so, it seems like both a somewhat low-risk, but also low-reward
approach.

It's low-risk since if it doesn't work, they're already beating folks on
launch costs, so if this fails, they're not out anything. Their business
model doesn't depend on ths.

On the other hand, recovering a single Merlin won't save them that much
money. And if BFR is so close flying, what's the point?

I mean I think it's pretty cool, but ultimately, I wonder who much it'll be
worth the trouble. (assuming they do catch the thing somewhere in the
Pacific, they still have to then get it back to the US mainland.)

Though, it suddenly dawns on me, heck, save the engine, forget the tanks and
you can fly the engine home in a air-freighter and still save the most
costly item.

  #2  
Old April 18th 18, 01:05 AM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,307
Default Space X 2nd stage recovery

In article ,
says...

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

I find this interesting for a couple of reasons.

The approach is interesting and I wonder who much it'll impact the final
payload numbers.


On Falcon 9 the mass of the system would be fairly critical so they
might not be able to recover very many of those stages. But on Falcon
Heavy, the mass penalty wouldn't matter much, so you'd think they could
try to recover many more.

But more so, it seems like both a somewhat low-risk, but also low-reward
approach.

It's low-risk since if it doesn't work, they're already beating folks on
launch costs, so if this fails, they're not out anything. Their business
model doesn't depend on ths.

On the other hand, recovering a single Merlin won't save them that much
money. And if BFR is so close flying, what's the point?


Practice for the upper stage of BFR. More engineering data. Even when
SpaceX doesn't plan to recover a Falcon 9 first stage, they've been
using them for test "landings" in the ocean in order to gather more data
on "hotter" reentry and landings.

I mean I think it's pretty cool, but ultimately, I wonder who much it'll be
worth the trouble. (assuming they do catch the thing somewhere in the
Pacific, they still have to then get it back to the US mainland.)

Though, it suddenly dawns on me, heck, save the engine, forget the tanks and
you can fly the engine home in a air-freighter and still save the most
costly item.


I doubt SpaceX would do that. They'd want the whole stage back for
inspection, even if the engine is the only thing they can actually
reuse. Again, more engineering data.

Build a little, test a little, fly a little. That's how they're gaining
their experience in reuse.

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.
  #3  
Old April 18th 18, 05:53 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default Space X 2nd stage recovery

Jeff Findley wrote on Tue, 17 Apr 2018
20:05:43 -0400:

In article ,
says...

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

I find this interesting for a couple of reasons.

The approach is interesting and I wonder who much it'll impact the final
payload numbers.


On Falcon 9 the mass of the system would be fairly critical so they
might not be able to recover very many of those stages. But on Falcon
Heavy, the mass penalty wouldn't matter much, so you'd think they could
try to recover many more.

But more so, it seems like both a somewhat low-risk, but also low-reward
approach.

It's low-risk since if it doesn't work, they're already beating folks on
launch costs, so if this fails, they're not out anything. Their business
model doesn't depend on ths.

On the other hand, recovering a single Merlin won't save them that much
money. And if BFR is so close flying, what's the point?


Practice for the upper stage of BFR. More engineering data. Even when
SpaceX doesn't plan to recover a Falcon 9 first stage, they've been
using them for test "landings" in the ocean in order to gather more data
on "hotter" reentry and landings.

I mean I think it's pretty cool, but ultimately, I wonder who much it'll be
worth the trouble. (assuming they do catch the thing somewhere in the
Pacific, they still have to then get it back to the US mainland.)

Though, it suddenly dawns on me, heck, save the engine, forget the tanks and
you can fly the engine home in a air-freighter and still save the most
costly item.


I doubt SpaceX would do that. They'd want the whole stage back for
inspection, even if the engine is the only thing they can actually
reuse. Again, more engineering data.

Build a little, test a little, fly a little. That's how they're gaining
their experience in reuse.


Oh, I didn't mention it before, but if you're using Falcon Heavy for
Moon missions, you're using it in expendable mode because if you try
to recover the cores you have nowhere near enough boost for those
missions.


--
"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
  #4  
Old April 18th 18, 10:18 AM posted to sci.space.policy
Sylvia Else
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Posts: 1,063
Default Space X 2nd stage recovery

On 18/04/2018 5:19 AM, Greg (Strider) Moore wrote:
https://www.space.com/40313-spacex-r...y-balloon.html

I find this interesting for a couple of reasons.

The approach is interesting and I wonder who much it'll impact the final
payload numbers.

But more so, it seems like both a somewhat low-risk, but also low-reward
approach.

It's low-risk since if it doesn't work, they're already beating folks on
launch costs, so if this fails, they're not out anything. Their business
model doesn't depend on ths.

On the other hand, recovering a single Merlin won't save them that much
money. And if BFR is so close flying, what's the point?

I mean I think it's pretty cool, but ultimately, I wonder who much it'll
be worth the trouble. (assuming they do catch the thing somewhere in the
Pacific, they still have to then get it back to the US mainland.)

Though, it suddenly dawns on me, heck, save the engine, forget the tanks
and you can fly the engine home in a air-freighter and still save the
most costly item.


This may be more about symbolism than economics. If he can recover the
second stage, as well as the cowling, then he'll have a 100% reusable
launcher.

Sylvia.
  #5  
Old April 18th 18, 09:27 PM 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 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.



Is this a case of planning bouyancy such that it is massively positive
initially to slow down descent, but as it drops into denser atmpsphere,
bouyancy dimonishes and they plan it such that it gets to just a tad
below neutral bouyancy for a gentle touch down with the engine firing to
stop vertical speed just bfore touching ground?

Are we talking langing legs and fins?

Or is this going to be dead weight falling back help by a balloon and
truly fall on some mattress factury like when Batman and Robin had
engine problems in a helicopter?


Did you read any of the article?


How would de-orbit work? From the point stage-2 is no longer needed for
payload, isn't it firmly in orbit and coudl stay there for very long
time? I assume it would require de-orbit burn?


They already deorbit the 2nd stages to reduce the orbital debris problem




--
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  #6  
Old April 19th 18, 01:06 AM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,307
Default Space X 2nd stage recovery

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
--
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.
  #7  
Old April 19th 18, 01:50 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default Space X 2nd stage recovery

JF Mezei wrote on Wed, 18 Apr 2018
03:24:19 -0400:

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).


Think about the physics. It's going to be almost all drag initially
(not much to displace at high altitudes) with gradually increasing
lift as it drops lower.


Is this a case of planning bouyancy such that it is massively positive
initially to slow down descent, but as it drops into denser atmpsphere,
bouyancy dimonishes and they plan it such that it gets to just a tad
below neutral bouyancy for a gentle touch down with the engine firing to
stop vertical speed just bfore touching ground?


That would sort of violate the laws of physics. Note that the ship
they're talking about using to 'catch' it is intended to catch free
falling objects (like fairings).


Are we talking langing legs and fins?


No.


Or is this going to be dead weight falling back help by a balloon and
truly fall on some mattress factury like when Batman and Robin had
engine problems in a helicopter?


That, except it's more of a 'net' than a "mattress factory". Did you
actually read the article, Mayfly, or is it that you've forgotten what
it said in the time it's taken you to write this. Again, think about
the physics. A balloon greatly increases the drag, which I'd bet is
the primary slowing method. I wouldn't be surprised if the balloon is
designed to be 'parafoil-like' at low altitudes so it can be steered
somewhat.


How would de-orbit work? From the point stage-2 is no longer needed for
payload, isn't it firmly in orbit and coudl stay there for very long
time? I assume it would require de-orbit burn?


They already do a commanded deorbit burn to drop the stages in the
Pacific so they're not cluttering up orbital space. They would just
target the reentry point closer to land instead of out in the Pacific
and stick a 'catcher' ship out there. This is all described in the
article, which you have apparently forgotten the content of in true
Mayfly fashion.

I would expect this, like fairing recovery, to have a pretty low
chance of success.


--
"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
  #8  
Old April 19th 18, 09:20 PM posted to sci.space.policy
David Spain
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Posts: 2,901
Default Space X 2nd stage recovery

On 4/17/2018 3:19 PM, Greg (Strider) Moore wrote:
https://www.space.com/40313-spacex-r...y-balloon.html

I find this interesting for a couple of reasons.

The approach is interesting and I wonder who much it'll impact the final
payload numbers.

But more so, it seems like both a somewhat low-risk, but also low-reward
approach.


I remember years back when Musk first propose recovering Falcon 9 stages
that the topic of a ballute came up on the a-rocket mailing list,
ostensibly as a way to recover the 2nd stage short of propulsive landing.

It's low-risk since if it doesn't work, they're already beating folks on
launch costs, so if this fails, they're not out anything. Their business
model doesn't depend on ths.

On the other hand, recovering a single Merlin won't save them that much
money. And if BFR is so close flying, what's the point?


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

I mean I think it's pretty cool, but ultimately, I wonder who much it'll
be worth the trouble. (assuming they do catch the thing somewhere in the
Pacific, they still have to then get it back to the US mainland.)

Though, it suddenly dawns on me, heck, save the engine, forget the tanks
and you can fly the engine home in a air-freighter and still save the
most costly item.


I suspect this is (primarily) research on ballutes for use on other
future projects. You are getting high altitude from orbit returns for
free. Why not take advantage?

Jeff Findley writes:
Build a little, test a little, fly a little. That's how they're gaining
their experience in reuse


That how they've gained lots of kinds of experience...

Dave


  #9  
Old April 19th 18, 11:22 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default Space X 2nd stage recovery

JF Mezei wrote on Thu, 19 Apr 2018
18:05:00 -0400:

On 2018-04-18 20:50, Fred J. McCall wrote:

That would sort of violate the laws of physics.


Not necessarily. Your giant balloon will shrink as it falls into denser
atmosphere. IF the ration of weight of gas inside balloon vs weight of
air being displaced by balloon changes, then bouyancy changes.


Yes, but likely not the way YOU want it to.


Note that the ship
they're talking about using to 'catch' it is intended to catch free
falling objects (like fairings).


Then if it falls on a mattress/net, what are the odds that it remain in
usable state?


Pretty good if they can actually catch it.


If they catch it in the air by the balloon, can the heliocopter land
the hanging stage II onto some sort of receptable on ground that will
provide proper support so it isn't dropped on engine bell with
expectation it remain standing without damage?


If they catch it by using guys Roman riding on teams of Pegasi, they
can just fly it back to land. Any other moot speculation you'd care
to engage in? The idea is for it to hit the net. Did you even bother
to read the ****ing article that was linked?


They already do a commanded deorbit burn to drop the stages in the
Pacific so they're not cluttering up orbital space.


Thanks. wasn't aware of that.


It was in the linked article. So either you didn't read it or your
famous memory is once again in play.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #10  
Old April 19th 18, 11:26 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default Space X 2nd stage recovery

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.


--
"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
 




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