Author Topic: Falcon 9 upper stage controlled descent tests?  (Read 14537 times)

Offline Llian Rhydderch

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Falcon 9 upper stage controlled descent tests?
« on: 05/06/2014 11:44 PM »
At some point, SpaceX will begin to do some controlled descent stage tests on the Falcon 9 second stage, on an otherwise used-up and economically worthless upper stage, after its productive use on a paid-for orbital mission.

Analogous to the controlled descent flight tests and over-ocean simulated landings they began on the boosters with the CASSIOPE and CRS-3 missions, SpaceX can learn something from each part of the expansion of the descent flight envelope--at least until the no-Thermal-Protection-System (noTPS) upper stage begins to breakup--even as the used US ultimately breaks up, burns up, and craters into the surf, where it was headed anyway.

My questions: 

 - How early can SpaceX begin to learn from any phase of that reentry to begin growing their own data bank for their reusable-team engineers? 

 - Might that time be now, in 2Q2014?  SpaceX has been known to have many parts of various development and test programs well underway before they publicly announce that they are doing them. 

 - What sort of radar/tracking assets might exist that would make tracking the descent possible at various parts of it's reentry trajectory over the Indian Ocean, the path used to force deorbit both the CRS-3 US and the Orbcomm OG2 US in April/May 2014, where SpaceX could buy or lease such services to obtain the radar and telemetry data they want?

 - What sort of engineering things might be learned from a more-heavily-instrumented F9 US reentry with good US-to-ground telemetry and radar coverage?

 - Might it help to add Reaction Control System (RCS) thrusters to an early US, even before adding any TPS, in order to learn upper atmosphere stage dynamics prior to breakup?  (analogous to what SpaceX learned on the first booster return: that their gaseous nitrogen RCS was apparently undersized, so they doubled it for CRS-3)

 - Does SpaceX have sufficient resources and capital to begin expending development/test expenses on the second stage aspects of their multi-phase reusable launch vehicle technology development program?  And related, is it worth it, from a cost/benefit point of view? 

 - How might such data inform the design of the F9 reusable upper stage, the one that will ostensibly be designed to incorporate a TPS so it can make it through the atmospheric reentry and landing legs to, ultimately, land on terra firma?

I look forward to your thoughts and analysis.


Mods:  I could not find another thread in this section that dealt with this topic.  If such exists, feel free to move my post to that thread.
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Offline Llian Rhydderch

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #1 on: 05/07/2014 12:22 AM »
To kick it off with just one small question, the Orbcomm OG2 second stage debris area in the Indian Ocean was published on the OG2 pre-launch updates thread a few hours ago.

Navigational warning for 2nd stage debris
valid May 10 from 1449 to 1551UTC
alternate May 11 from 1427 to 1529UTC




That is (conveniently?) off the southwest coast of Australia.

Are there any good radar tracking stations and/or telemetry receiving stations south of Perth that might be able to capture some useful part of the high-altitude descent path?

Or might the reentry into the upper atmosphere be so far ahead of the debris area that tracking assets located in Australia would not prove useful anyway?
Re arguments from authority on NSF:  "no one is exempt from error, and errors of authority are usually the worst kind.  Taking your word for things without question is no different than a bracket design not being tested because the designer was an old hand."
"You would actually save yourself time and effort if you were to use evidence and logic to make your points instead of wrapping yourself in the royal mantle of authority.  The approach only works on sheep, not inquisitive, intelligent people."

Offline CJ

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #2 on: 05/07/2014 05:40 AM »
That debris area indicates that the area of upper altitude reentry they'd be interested in having radar coverage is roughly west of Perth, about  thousand miles out. That'd put it in the coverage area of the Jindalee over-the-horizon back-scatter radar. Whether they actually did this or not I have no idea, but it would be within range.

Offline cleonard

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #3 on: 05/07/2014 05:59 AM »
One issue for telemetry is the radio blackout that is due to the plasma surrounding the spacecraft.  There is a cutoff frequency below which the plasma blocks the radio signals.  The cutoff frequency is roughly proportional to the square root of the plasma density.  There are a lot of variables, but if I remember correctly at the peak plasma density you will need to be above 10 GHz or so to get the signal through. 

All of your significant data gathering will be when the stage is surrounded with that plasma.

Of course the plasma is far from uniform.  Trail an antenna out the back end and it's  a lot easier to maintain communications.  Not exactly pointed in the right direction, but a TDRSS link might be worth the cost.

Offline Jim

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #4 on: 05/07/2014 12:44 PM »


Are there any good radar tracking stations


There are few of those (that can do skin track) and are basically limited to US installations.

Offline JasonAW3

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #5 on: 05/07/2014 03:28 PM »
As I remember NASA USED to maintain a fairly comprehensive tracking station that included a variety of Radar systems in Austrailia.  But this was back during Apolloand as such, most of this equipment was likely rendered obsolite and dismantled.
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Offline Jim

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #6 on: 05/07/2014 04:07 PM »
As I remember NASA USED to maintain a fairly comprehensive tracking station that included a variety of Radar systems in Austrailia.  But this was back during Apolloand as such, most of this equipment was likely rendered obsolite and dismantled.

Not all tracking stations have radar

Offline DavidH

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #7 on: 05/07/2014 05:38 PM »
As I remember NASA USED to maintain a fairly comprehensive tracking station that included a variety of Radar systems in Austrailia.  But this was back during Apolloand as such, most of this equipment was likely rendered obsolite and dismantled.
Are you talking about the DSN?
Canberra is still part of the DSN.
http://www.cdscc.nasa.gov/
http://en.wikipedia.org/wiki/Canberra_Deep_Space_Communication_Complex
Edit: Oh. Probably Carnavon Tracking Station. http://en.wikipedia.org/wiki/Carnarvon_Tracking_Station
« Last Edit: 05/07/2014 05:39 PM by DavidH »
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Offline yg1968

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #8 on: 05/07/2014 06:52 PM »
Could the second stage eventually land in Australia? Would that be a problem from an ITAR perspective?

Offline Llian Rhydderch

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #9 on: 05/07/2014 06:59 PM »
Could the second stage eventually land in Australia? Would that be a problem from an ITAR perspective?

Hmmm.  I had not thought of that.

My first reaction though is why would it be economically beneficial to land in Australia.

Since the 2nd stage is in LEO by the end of the planned burn, one can just wait ten or twenty orbits for it to realign with the site where it launched. 

Of course, that is not at no cost.  The second stage needs to be designed for sufficient on-orbit duration so it has full control after whatever time it requires for the re-alignment, and maybe the weather?, to cooperate to attempt its controlled descent.
Re arguments from authority on NSF:  "no one is exempt from error, and errors of authority are usually the worst kind.  Taking your word for things without question is no different than a bracket design not being tested because the designer was an old hand."
"You would actually save yourself time and effort if you were to use evidence and logic to make your points instead of wrapping yourself in the royal mantle of authority.  The approach only works on sheep, not inquisitive, intelligent people."

Offline Jim

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #10 on: 05/07/2014 08:24 PM »
Could the second stage eventually land in Australia? Would that be a problem from an ITAR perspective?

That would be only applicable to ISS or Orbcomm type trajectories (inclinations in the 50's)

Offline Thorny

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #11 on: 05/07/2014 08:39 PM »
Could the second stage eventually land in Australia? Would that be a problem from an ITAR perspective?

That would be only applicable to ISS or Orbcomm type trajectories (inclinations in the 50's)

Due east, too. There is plenty of Australia north of 28.5 deg S. latitude. A couple of good RAAF bases in Western Australia, and Perth is close to the groundtrack at 31 deg S.

Offline Jim

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #12 on: 05/07/2014 08:55 PM »

Due east, too. There is plenty of Australia north of 28.5 deg S. latitude. A couple of good RAAF bases in Western Australia, and Perth is close to the groundtrack at 31 deg S.

For due east missions, which are typically GTO, the upperstage would be close to GSO altitude while passing near Australia.   And some missions take out some of the inclination in the GTO burn.
« Last Edit: 05/07/2014 08:56 PM by Jim »

Offline Llian Rhydderch

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #13 on: 05/07/2014 10:03 PM »
FWIW, the OP on this thread was looking for info on early TESTS of the controlled descents, which will probably be over the ocean for a while, just like the F9 booster return controlled descent tests that began on regular old F9 missions last September.

The speculation on land landings on the continent of Australia might be just a tad premature.   ;)


Edit:  tweaked
« Last Edit: 05/07/2014 10:05 PM by Llian Rhydderch »
Re arguments from authority on NSF:  "no one is exempt from error, and errors of authority are usually the worst kind.  Taking your word for things without question is no different than a bracket design not being tested because the designer was an old hand."
"You would actually save yourself time and effort if you were to use evidence and logic to make your points instead of wrapping yourself in the royal mantle of authority.  The approach only works on sheep, not inquisitive, intelligent people."

Offline Space Ghost 1962

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #14 on: 05/07/2014 11:07 PM »
At some point, SpaceX will begin to do some controlled descent stage tests on the Falcon 9 second stage, on an otherwise used-up and economically worthless upper stage, after its productive use on a paid-for orbital mission.

Analogous to the controlled descent flight tests and over-ocean simulated landings they began on the boosters with the CASSIOPE and CRS-3 missions, SpaceX can learn something from each part of the expansion of the descent flight envelope--at least until the no-Thermal-Protection-System (noTPS) upper stage begins to breakup--even as the used US ultimately breaks up, burns up, and craters into the surf, where it was headed anyway.

My questions: 

1 - How early can SpaceX begin to learn from any phase of that reentry to begin growing their own data bank for their reusable-team engineers? 

2 - Might that time be now, in 2Q2014?  SpaceX has been known to have many parts of various development and test programs well underway before they publicly announce that they are doing them. 

3 - What sort of radar/tracking assets might exist that would make tracking the descent possible at various parts of it's reentry trajectory over the Indian Ocean, the path used to force deorbit both the CRS-3 US and the Orbcomm OG2 US in April/May 2014, where SpaceX could buy or lease such services to obtain the radar and telemetry data they want?

4 - What sort of engineering things might be learned from a more-heavily-instrumented F9 US reentry with good US-to-ground telemetry and radar coverage?

5 - Might it help to add Reaction Control System (RCS) thrusters to an early US, even before adding any TPS, in order to learn upper atmosphere stage dynamics prior to breakup?  (analogous to what SpaceX learned on the first booster return: that their gaseous nitrogen RCS was apparently undersized, so they doubled it for CRS-3)

6 - Does SpaceX have sufficient resources and capital to begin expending development/test expenses on the second stage aspects of their multi-phase reusable launch vehicle technology development program?  And related, is it worth it, from a cost/benefit point of view? 

7 - How might such data inform the design of the F9 reusable upper stage, the one that will ostensibly be designed to incorporate a TPS so it can make it through the atmospheric reentry and landing legs to, ultimately, land on terra firma?

I look forward to your thoughts and analysis.


Mods:  I could not find another thread in this section that dealt with this topic.  If such exists, feel free to move my post to that thread.

1. US is not designed as a RV of any kind. The beginning of any experiment would be to have an achievable objective, a means to return data such that you could determine how/if the objective is being achieved (or not), a safety assessment/protocol to insure risk management, and requirements of systems to achieve objective that would not compromise the related primary mission and its objectives. Considerable work. It's not a passively stable object by a long short, a specialized strap down guidance system with a difficult to prove guidance model seems also a key need.

2. Not likely. Too much too soon. Too easy to compromise launch services when you want to prove yourself.

3. You need tracking, high resolution radar,  and telemetry. You may also wish to recover debris with hazardous substances. These do exist in relevant areas of the globe. One can keep alive the stage and wait for the ground track given the risk is acceptable - usually they are short lived - hours to half a day.

4. Means to stabilize and guide a reentering stage with precision. Aeroloads and turbulence. Decelleration profile. Actual data as opposed to CFD/wind tunnel models. Trajectory analysis to compare against computational models. Experience in managing the flight profiles of a returning stage to a nervous regulatory authorities with little comfort for this. TPS but this is least of concern WRT the rest.

5. Has one already. May have insufficient control authority and propellant.

6. Unknown.

7. They already do all of this with Dragon. US's CG, aerodynamics, ... all wrong for a RV. In solving this you create something unlike a US with unpredictable economics. It would be a gamble that the systems could be changed little enough to yield a useful, reflyable US. Stabilizing and precision guidance of a US through a possibly high energy orbit would be a significant accomplishment along the path to recovery.

8. You're not listing safety here - its a major issue. Proving you won't mess things up or have it slam into someone is a major concern. What do you do when your experiment fails? Where does the debris go? You might bounce off track.

Offline Lar

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #15 on: 05/08/2014 05:28 AM »
So plasma means not getting data back easily...

Once the stage can reliably get through that part is there merit in making up something to record and retransmit telemetry? It sounds like it might be doable but is the window of usefulness too small? (it's not useful until you can get through the high plasma part of reentry repeatedly.... it's not useful after you are getting all the way back reliably)

I think I just answered my own question.

So then, how long does a trailing wire antenna need to be in order to transmit? And wouldn't it tend to get damaged close to the stage? How much mass would something like that add? what if it came unreeled too early? That could risk mission loss.
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Offline Jim

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #16 on: 05/08/2014 12:13 PM »
So plasma means not getting data back easily...

Once the stage can reliably get through that part is there merit in making up something to record and retransmit telemetry? It sounds like it might be doable but is the window of usefulness too small? (it's not useful until you can get through the high plasma part of reentry repeatedly.... it's not useful after you are getting all the way back reliably)

I think I just answered my own question.

So then, how long does a trailing wire antenna need to be in order to transmit? And wouldn't it tend to get damaged close to the stage? How much mass would something like that add? what if it came unreeled too early? That could risk mission loss.

The shuttle could transmit to TDRS because there a hole in the back side plasma due to the large vehicle planform.  The second stage is probably to small for this.  Also, I don't think trailing wire would work for S-band/TDRS and would also likely burn off.

Online ugordan

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #17 on: 05/08/2014 01:10 PM »
The shuttle could transmit to TDRS because there a hole in the back side plasma due to the large vehicle planform.  The second stage is probably to small for this.  Also, I don't think trailing wire would work for S-band/TDRS and would also likely burn off.

I thought it was a matter of frequency used? For example the latter Mars landers had telemetry received by orbiting assets with no blackout periods.

Offline MP99

Re: Falcon 9 upper stage controlled descent tests?
« Reply #18 on: 05/08/2014 01:43 PM »
8. You're not listing safety here - its a major issue. Proving you won't mess things up or have it slam into someone is a major concern. What do you do when your experiment fails? Where does the debris go? You might bounce off track.

And some of the experiments may reduce the breakup of the stage on reentry, increasing the size of pieces that might reach the ground intact.

cheers, Martin

Offline Jim

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #19 on: 05/08/2014 02:23 PM »
I thought it was a matter of frequency used? For example the latter Mars landers had telemetry received by orbiting assets with no blackout periods.

They were large disks and had antennas placed in the middle of them.  On a upperstage, the antennas are usual on the sides.  It is hard to put an antenna on the engine nozzle or payload adapter depending on which end enters first ;-)

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