Author Topic: F9 Second Stage Reusability  (Read 139148 times)

Offline Space Ghost 1962

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Re: F9 Second Stage Reusability
« Reply #140 on: 04/04/2017 09:41 PM »
Keep in mind what is claimed for fairing recovery - thruster packs that stabilize entry.

Fairings and US's are alike in being "fluffy".

They now have experience and flight data in hypersonic entry stabilization.

So you can apply that to a computer model of the US. That gives you a props usage expectation for the stage.

You then adjust the US/RV model with thruster positions/authority and rerun sims, doing trade-offs.

The benefit of a FH Demo flight to do this on is that you class the additions as part of the payload weight - so what if your mass simulator is 53-2t instead of 53t.

Offline Rocket Science

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Re: F9 Second Stage Reusability
« Reply #141 on: 04/04/2017 09:52 PM »
The problem remains how to you ensure that a rear heavy cylinder stays nose down when every slightest disturbance wants to push it nose up, if not into an active end over end tumble.

"Drag" something behind it.
That's what my petals do create drag...
« Last Edit: 04/04/2017 10:02 PM by Rocket Science »
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Offline envy887

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Re: F9 Second Stage Reusability
« Reply #142 on: 04/04/2017 10:02 PM »
My bet is what user NovaSilisko suggested year ago.

https://forum.nasaspaceflight.com/index.php?topic=39314.msg1474695#msg1474695

His post has a nice picture, in a nutshell - like a bottom half of Dragon2 attached to the top of S2 legs forward.

P.S. If it adds 4000kg to the mass of S2, so be it. Good for experimenting when the payload to LEO allows it.
Those people who've read "Frontiers of Space" by Bono & Gatland will recognize Bono's idea for an early PoC of Saturn 2nd stage reuse, including the nose landing scheme.

The problem remains how to you ensure that a rear heavy cylinder stays nose down when every slightest disturbance wants to push it nose up, if not into an active end over end tumble.

The stage probably isn't that rear-heavy. The Mvac is only ~500 kg without the nozzle (which likely adds a few hundred kg). A frontal heatshield probably weighs nearly that much, which would return the COM to near the COP.

Add on a few deployable PICA-covered split flaps (like IXV, but launched inside the interstage) to move the COP further back and enter like a shuttlecock. Pop a guided chute and land in a bouncy castle like the fairings.

Offline Wolfram66

Re: F9 Second Stage Reusability
« Reply #143 on: 04/04/2017 10:07 PM »
My bet is what user NovaSilisko suggested year ago.

https://forum.nasaspaceflight.com/index.php?topic=39314.msg1474695#msg1474695

His post has a nice picture, in a nutshell - like a bottom half of Dragon2 attached to the top of S2 legs forward.

P.S. If it adds 4000kg to the mass of S2, so be it. Good for experimenting when the payload to LEO allows it.
Those people who've read "Frontiers of Space" by Bono & Gatland will recognize Bono's idea for an early PoC of Saturn 2nd stage reuse, including the nose landing scheme.

The problem remains how to you ensure that a rear heavy cylinder stays nose down when every slightest disturbance wants to push it nose up, if not into an active end over end tumble.

The stage probably isn't that rear-heavy. The Mvac is only ~500 kg without the nozzle (which likely adds a few hundred kg). A frontal heatshield probably weighs nearly that much, which would return the COM to near the COP.

Add on a few deployable PICA-covered split flaps (like IXV, but launched inside the interstage) to move the COP further back and enter like a shuttlecock. Pop a guided chute and land in a bouncy castle like the fairings.

better to have a PICA-X nose on the S2 with a Ballute collar like the LDSD. that will work with initial atmospheric interface as well as post max-heating while falling tail first. shuttlecock would probably fold up like an umbrella in the wind. IMHO

Offline GWH

Re: F9 Second Stage Reusability
« Reply #144 on: 04/04/2017 10:08 PM »
The problem remains how to you ensure that a rear heavy cylinder stays nose down when every slightest disturbance wants to push it nose up, if not into an active end over end tumble.

"Drag" something behind it.

Like a really big nozzle extension?

Would this in itself be enough to shift CP behind COG though?   
Spaceflight 101 estimates approx 4000kg for total stage, 490kg of which is Mvac.
« Last Edit: 04/04/2017 10:08 PM by GWH »

Offline Rocket Science

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Re: F9 Second Stage Reusability
« Reply #145 on: 04/04/2017 10:21 PM »
My bet is what user NovaSilisko suggested year ago.

https://forum.nasaspaceflight.com/index.php?topic=39314.msg1474695#msg1474695

His post has a nice picture, in a nutshell - like a bottom half of Dragon2 attached to the top of S2 legs forward.

P.S. If it adds 4000kg to the mass of S2, so be it. Good for experimenting when the payload to LEO allows it.
Those people who've read "Frontiers of Space" by Bono & Gatland will recognize Bono's idea for an early PoC of Saturn 2nd stage reuse, including the nose landing scheme.

The problem remains how to you ensure that a rear heavy cylinder stays nose down when every slightest disturbance wants to push it nose up, if not into an active end over end tumble.

The stage probably isn't that rear-heavy. The Mvac is only ~500 kg without the nozzle (which likely adds a few hundred kg). A frontal heatshield probably weighs nearly that much, which would return the COM to near the COP.

Add on a few deployable PICA-covered split flaps (like IXV, but launched inside the interstage) to move the COP further back and enter like a shuttlecock. Pop a guided chute and land in a bouncy castle like the fairings.

better to have a PICA-X nose on the S2 with a Ballute collar like the LDSD. that will work with initial atmospheric interface as well as post max-heating while falling tail first. shuttlecock would probably fold up like an umbrella in the wind. IMHO
They would be controlled by actuators, just like the Shuttle's body flap...
https://spaceflight.nasa.gov/shuttle/reference/shutref/structure/bodyflap.html
« Last Edit: 04/04/2017 10:26 PM by Rocket Science »
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Online wannamoonbase

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Re: F9 Second Stage Reusability
« Reply #146 on: 04/04/2017 10:23 PM »
My bet is what user NovaSilisko suggested year ago.

https://forum.nasaspaceflight.com/index.php?topic=39314.msg1474695#msg1474695

His post has a nice picture, in a nutshell - like a bottom half of Dragon2 attached to the top of S2 legs forward.

P.S. If it adds 4000kg to the mass of S2, so be it. Good for experimenting when the payload to LEO allows it.
Those people who've read "Frontiers of Space" by Bono & Gatland will recognize Bono's idea for an early PoC of Saturn 2nd stage reuse, including the nose landing scheme.

The problem remains how to you ensure that a rear heavy cylinder stays nose down when every slightest disturbance wants to push it nose up, if not into an active end over end tumble.

The stage probably isn't that rear-heavy. The Mvac is only ~500 kg without the nozzle (which likely adds a few hundred kg). A frontal heatshield probably weighs nearly that much, which would return the COM to near the COP.

Add on a few deployable PICA-covered split flaps (like IXV, but launched inside the interstage) to move the COP further back and enter like a shuttlecock. Pop a guided chute and land in a bouncy castle like the fairings.

I agree, this is the most likely configuration.  The PICA shield, landing legs and landing Draco's could come  Dragon V2. 

Using the Merlin for landing doesn't work for a few reasons, but the show stopper to me seems to be the heating or lose of cryogenic fuel.  Maybe it can do the retro burn or orbit reduction, as long as it's not too long after the mission is completed.

The cross range on the US and where it might bre able to land is an issue too.  With Draco's perhaps they could target a landing location at a time when orbital mechanics work out.
SpaceX, just a few things planned for 2018: FH, Starlink Prototypes, Block 5, Dragon 2, Increased launch rate.

Offline envy887

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Re: F9 Second Stage Reusability
« Reply #147 on: 04/04/2017 10:24 PM »
My bet is what user NovaSilisko suggested year ago.

https://forum.nasaspaceflight.com/index.php?topic=39314.msg1474695#msg1474695

His post has a nice picture, in a nutshell - like a bottom half of Dragon2 attached to the top of S2 legs forward.

P.S. If it adds 4000kg to the mass of S2, so be it. Good for experimenting when the payload to LEO allows it.
Those people who've read "Frontiers of Space" by Bono & Gatland will recognize Bono's idea for an early PoC of Saturn 2nd stage reuse, including the nose landing scheme.

The problem remains how to you ensure that a rear heavy cylinder stays nose down when every slightest disturbance wants to push it nose up, if not into an active end over end tumble.

The stage probably isn't that rear-heavy. The Mvac is only ~500 kg without the nozzle (which likely adds a few hundred kg). A frontal heatshield probably weighs nearly that much, which would return the COM to near the COP.

Add on a few deployable PICA-covered split flaps (like IXV, but launched inside the interstage) to move the COP further back and enter like a shuttlecock. Pop a guided chute and land in a bouncy castle like the fairings.

better to have a PICA-X nose on the S2 with a Ballute collar like the LDSD. that will work with initial atmospheric interface as well as post max-heating while falling tail first. shuttlecock would probably fold up like an umbrella in the wind. IMHO
They would be controlled by actuators, just like the Shuttle's body flap...

Or like an air brake

Offline envy887

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Re: F9 Second Stage Reusability
« Reply #148 on: 04/04/2017 10:29 PM »
That's what my petals do create drag...

That's the idea, but those are probably 4x longer then they need to be. Don't want to cover up the MVac nozzle, it needs to radiate heat.

A relatively small amount of "draggy" area will be more than enough to make it stable. The inflatable toroid is also a great concept.

Offline sevenperforce

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Re: F9 Second Stage Reusability
« Reply #149 on: 04/04/2017 10:40 PM »
That's what my petals do create drag...

That's the idea, but those are probably 4x longer then they need to be. Don't want to cover up the MVac nozzle, it needs to radiate heat.

A relatively small amount of "draggy" area will be more than enough to make it stable. The inflatable toroid is also a great concept.
An inflatable toroid could conceivably be packed around the base of the MVac. There's plenty of space. If the toroid had TPS on it, that would also protect the rather fragile engine bell.

Offline Wolfram66

Re: F9 Second Stage Reusability
« Reply #150 on: 04/04/2017 10:47 PM »
That's what my petals do create drag...

That's the idea, but those are probably 4x longer then they need to be. Don't want to cover up the MVac nozzle, it needs to radiate heat.

A relatively small amount of "draggy" area will be more than enough to make it stable. The inflatable toroid is also a great concept.

what happens when S2 flips to perform hypersonic retro-burn? are the pedals extended or retracted and what is the weight penalty for the pedal and actuator systems?   

just playing Satan's Barrister aka: Devil's Advocate  :o ;D

Offline envy887

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Re: F9 Second Stage Reusability
« Reply #151 on: 04/04/2017 10:52 PM »
That's what my petals do create drag...

That's the idea, but those are probably 4x longer then they need to be. Don't want to cover up the MVac nozzle, it needs to radiate heat.

A relatively small amount of "draggy" area will be more than enough to make it stable. The inflatable toroid is also a great concept.

what happens when S2 flips to perform hypersonic retro-burn? are the pedals extended or retracted and what is the weight penalty for the pedal and actuator systems?   

just playing Satan's Barrister aka: Devil's Advocate  :o ;D

No flip or retroburn needed in the atmosphere; after the deorbit burn (in vacuum), the MVac does not relight. RCS reorients the stage for entry, and it maintains that orientation all the way to the ground. Landing either on dedicated thrusters or an airbag.

Offline uhuznaa

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Re: F9 Second Stage Reusability
« Reply #152 on: 04/04/2017 11:00 PM »
I've often wondered why SpaceX didn't go with a plug nozzle type engine for the second stage.  It would do double duty as the heat shield.  It was considered for the second stage of Saturn IB and Saturn V before they were cancelled.  It was based on the J2 engine at that time.  The Octoweb is almost like a plug nozzle using he engines as heat shield for the first stage.  I know it might be more expensive to develop, but in the long run to get 2nd stage reusable, it may be the best overall to do.  No need for heat resistant nose or sides, parachutes, etc.  Just landing legs like the first stage.

Plug nozzles are heavy. They are basically a nozzle turned inside out, which means that the nozzle is surrounded by hot gas on all sides, so you have to actively cool it (or use ablative cooling, which is bad for reusability). Radiative cooling as with the current nozzle isn't possible then.

It would be an entirely different engine. You also still would need to have dedicated landing engines, since the main engine would be much too powerful for landing. Other than a bell nozzle it could adapt to sea level pressures though.

I mean, it's not a totally crazy idea. You could have the nozzle act as (part of a) heat shield and if you could throttle it deep enough you even might be able to land on it. You still would need very long and with that wide legs. And lots of development effort.

Offline Rocket Science

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Re: F9 Second Stage Reusability
« Reply #153 on: 04/04/2017 11:05 PM »
That's what my petals do create drag...

That's the idea, but those are probably 4x longer then they need to be. Don't want to cover up the MVac nozzle, it needs to radiate heat.

A relatively small amount of "draggy" area will be more than enough to make it stable. The inflatable toroid is also a great concept.
I made them long in order to protect the nozzle from entry heat, just like the Shuttle's body flap protected them. If you read my original post a couple of pages back I wrote in that they would move rearward, then expand in deployment in a controlled fashion, similar how an afterburner "turkey feathers" moves only outward more...#106
https://forum.nasaspaceflight.com/index.php?topic=42637.100
« Last Edit: 04/04/2017 11:21 PM by Rocket Science »
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Online spacenut

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Re: F9 Second Stage Reusability
« Reply #154 on: 04/04/2017 11:19 PM »
Here is some information on plug nozzle engines:

http://www.bing.com/images/search?view=detailV2&ccid=SoR555Fu&id=9C3B12E727ADA4CAD160E6E6B72DA3345FCE9E66&q=plug+nozzle+rocket+engine&simid=608008924879391049&selectedIndex=0

My idea was the simple inside out one round, not the linear one.  It was originally going to replace the J2 on the Saturn IB 2nd stage which was the same as the 3rd stage on Saturn V.  It was to return the 3rd stage to land using the engine as a heat shield.  They even built a J2 circular plug nozzle and tested it.  I just don't believe it would be that much heavier than adding a bunch of heat shield material to the sides of an upper stage or on top, and a shield to protect the engine. 

With the plug nozzle the engine becomes the heat shield on the way down.  Not much extra work other than legs, and being able to throttle down low enough to land the stage.  Look at the various pictures.  I'll try to find some more on the Saturn version.  The third stage was also suggested, that with the plug nozzle engine, it could become a small SSTO vehicle. 

Offline Jcc

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Re: F9 Second Stage Reusability
« Reply #155 on: 04/04/2017 11:49 PM »
That's what my petals do create drag...

That's the idea, but those are probably 4x longer then they need to be. Don't want to cover up the MVac nozzle, it needs to radiate heat.

A relatively small amount of "draggy" area will be more than enough to make it stable. The inflatable toroid is also a great concept.

what happens when S2 flips to perform hypersonic retro-burn? are the pedals extended or retracted and what is the weight penalty for the pedal and actuator systems?   

just playing Satan's Barrister aka: Devil's Advocate  :o ;D

No flip or retroburn needed in the atmosphere; after the deorbit burn (in vacuum), the MVac does not relight. RCS reorients the stage for entry, and it maintains that orientation all the way to the ground. Landing either on dedicated thrusters or an airbag.

The benefit of having TPS is that it can take the heating and bleed off most of the velocity from orbit. S1 has no TPS so has to do a reentry burn, S2 should not have to. It will need to do most of a full orbit to land back in the US, so most of the remaining fuel would probably be needed to achieve an orbital track that can get it to a convenient landing place, probably in California. Then, I figure dracos (not super dracos) would be enough to bring it out of orbit, then land with parachutes and airbags.

Offline CharlieWildman

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Re: F9 Second Stage Reusability
« Reply #156 on: 04/05/2017 01:02 AM »
That's what my petals do create drag...

That's the idea, but those are probably 4x longer then they need to be. Don't want to cover up the MVac nozzle, it needs to radiate heat.

A relatively small amount of "draggy" area will be more than enough to make it stable. The inflatable toroid is also a great concept.
I made them long in order to protect the nozzle from entry heat, just like the Shuttle's body flap protected them. If you read my original post a couple of pages back I wrote in that they would move rearward, then expand in deployment in a controlled fashion, similar how an afterburner "turkey feathers" moves only outward more...#106
https://forum.nasaspaceflight.com/index.php?topic=42637.100

Found this image searching Google for Falcon 9 second stage.  Small graphic image on the far right is interesting.
 http://blogs.esa.int/rocketscience/2014/04/22/dragon-lofts-cargo-to-the-iss/dragonlaunch_20140418_setp1/

A small amount of knowledge can be a dangerous thing.

Offline CharlieWildman

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Re: F9 Second Stage Reusability
« Reply #157 on: 04/05/2017 02:04 AM »
And of course we have this from a few years back.  Be interesting to know the full history of the image.
https://forum.nasaspaceflight.com/index.php?topic=36440.msg1308198#msg1308198
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Online ZachS09

Re: F9 Second Stage Reusability
« Reply #158 on: 04/05/2017 04:31 AM »
This is obviously not a finished design of the reusable second stage because there's no landing legs.

At least the aerosurfaces and heat shield are on this second stage.
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Online Gliderflyer

Re: F9 Second Stage Reusability
« Reply #159 on: 04/05/2017 05:03 AM »
This is obviously not a finished design of the reusable second stage because there's no landing legs.
That image appears to be from this 2008 paper, which puts it back in the parachute recovery era (no legs). Jon Goff had some posts on Selenian Boondocks about it back in the day:
http://selenianboondocks.com/2008/11/fun-spacex-paper-and-presentation/
http://selenianboondocks.com/2008/12/falcon-ix-upper-stage-recovery-kremlinology/

I don't know how applicable that image is to the current Falcon 9 upper stage, but it may be one of the simpler recovery options.
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