Author Topic: Falcon 9 upper stage controlled descent tests?  (Read 14962 times)

Online Llian Rhydderch

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #20 on: 05/08/2014 02:43 pm »
That is good info about telemetry during the plasma phase of reentry from several of you.

Question:  since any early tests of upper stage reentry on F9 missions is going to only apply to what might be learned before the stage breaks up, can someone describe the technical aspect of when the plasma begins on a non-TPS rocket body reentry and how soon after that the stage would typically break up? 

In other words, to get any data at all, must the transmission-in-the-midst-of-plasma problem be solved?  Or is there some useful part of the upper atmosphere reenty, where the plasma hasn't started yet, and SpaceX might learn something useful about how their particulary-shaped stage with a given density and CG might handle as it begins to encounter the upper atmosphere?  I'm wondering if an iterative program might get SpaceX any data at all from attempting to instrument the stage with some sensors/telemetry and studying the very early phase of US reentry.

And remember, it is possible that SpaceX might ignite the (expendable) second stage engine again, to change the velocity profile as the US begins reentry.  Why?  Simply in order to get test data for incremental improvement of their models, and to inform any design effort that might be underway.
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."
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Offline Elmar Moelzer

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #21 on: 05/08/2014 02:56 pm »
Hmm, what about a small eject able "black box" type of thing that stores the telemetry and is ejected the moment the stage breaks up. This could be triggered something like the launch abort type of trigger system. The data itself could probably fit on a micro SD card, or a combination of several (to provide redundancy), which are very small and lightweight. The bigger challenge might be to bring the thing down in one piece and the even bigger one would be finding it once it has landed, probably somewhere in the middle of the ocean. I am sure there are people on this board that have a better idea why this would or would not work (and what would be required to make it work).

Online Llian Rhydderch

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #22 on: 05/08/2014 03:12 pm »
BTW, just to put some reality in the types of trajectories that various upper stages might be flying on reentry, here is some info from another thread on the rentry of the F9 US from the Orbcomm OG2 M1 mission this weekend, which is reentering from a somewhat higher LEO of 715 km.  (Thanks to LouScheffer!)

I find it interesting that this mission will also make a 2nd stage disposal burn, based on this warning: http://forum.nasaspaceflight.com/index.php?topic=34591.msg1194554#msg1194554

Previously the F9v1.0 upper stages were allowed to naturally decay - but they seem to explicitly de-orbit the 2nd stage now for LEO (and near LEO) missions. Is this done to:
A. Gain confidence in upper stage restarts, or...
B. Be a good neighbor and dispose orbital debris quicker, or...
C. Practice 2nd stage reentry profiles, or...
D. All of the above?
(B) is legally required in this case.  The satellites will be dropped in a 715km x 715 km orbit. That's too high to meet the requirement for natural decay, which is re-entry within 25 years.  So they have to do something, at the very least to bring the perigee below about 400 km.  So you may as well burn a little longer and de-orbit deterministically, perhaps for the other reasons.
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 #23 on: 05/08/2014 03:19 pm »
Hmm, what about a small eject able "black box" type of thing that stores the telemetry and is ejected the moment the stage breaks up. This could be triggered something like the launch abort type of trigger system. The data itself could probably fit on a micro SD card, or a combination of several (to provide redundancy), which are very small and lightweight. The bigger challenge might be to bring the thing down in one piece and the even bigger one would be finding it once it has landed, probably somewhere in the middle of the ocean. I am sure there are people on this board that have a better idea why this would or would not work (and what would be required to make it work).

What protects the black box?

Offline Elmar Moelzer

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #24 on: 05/08/2014 03:49 pm »
What protects the black box?
That is a very good question.
Assuming that it can be made to be very small, it could probably also be made to be very tough with sufficient thermal protection and cushioning, without increasing size and weight too much to be feasible.
A lot of that would probably depend on how exactly this black box would work and what it would have to contain besides the 3 or 4 SD cards. I am a bit sketchy on that side. There are several options that I see:
1. The black box has a beacon with enough battery and floating device that allows it to be found drifting somewhere in the ocean after it comes down.
2. Maybe it will just keep transmitting the data after it has left the plasma black out and it does not have to be found at all. That might require it to transmit a lot of data within a comparably short timeframe though. Not sure whether is possible with a small, compact transmitter.
I admit that my understanding is lacking on many of these matters and I might be totally off with how much is required to make any of this work and it might just get too big to be feasible.
« Last Edit: 05/08/2014 03:50 pm by Elmar Moelzer »

Online RoboGoofers

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #25 on: 05/08/2014 05:40 pm »
What protects the black box?

What about something like the Stardust return vehicle? That looks about a meter in diameter, so probably even smaller.

Offline Space Ghost 1962

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #26 on: 05/08/2014 06:29 pm »
As to returning information, depends on the phase of reentry and the amount of information.

At EI, existing US telemetry works adequately. You can get kbps. What you are missing most is fine grain accelerometers and additional sensors to return interesting data til the plasma grows. You need something to listen to this and tracking/radar to correlate results, plus some kind of info on ionospheric densitys before hand - you get this by changing the radar's mode of operation to pulse heat region prior to entry to get density profile.  GNC results about maintaining attitude would be useful in establishing the hypersonic flight envelope and estimates on control authority and total propellant needs.

At some point you can't get the signal through. You either retain the data for transmission later, or transition to another comm technique. You can modulate the plasma wake either for indirect communication (reflected data), or with a means for using the wake as an antenna for extremely low bandwidth signals - "stable", "thermal", "shock". At this point the TPS/GNC performance of getting the intact stage lower/slower.

See Attitude Dynamics of Reentry Vehicle.

If you can make it past maxQ and max heating, the communications will start returning. If you can get a US to this point still intact, its about like first stage recovery issues. But as Martin above reminded, you now have a multi ton projectile at high Mach which might tumble - better have this cannonball aimed/oriented carefully as atmospheric pressure builds and control authority diminishes. Its at this point stability and guidance gets its acid test, one also might wish a breaking burn like first stage currently does to fall within a survivable aerodynamic envelope.

Then US falls, hopefully still in LOS of telemetry, and final braking of some sort and "landing".

add:
More I think about it, you can do some useful things with a largely unmodified US. There's a lot of drag/congestion with the nozzle/bell,  enough to be a significant heat shield all by itself.  And reentry tail first puts the CG and RCS in the right places, although the CP isn't. You program the stage guidance to stabilize using RCS tail s first and ride it down. From the ground, you optically sample and can determine composition, temperature of fireball to tell enough about stage's reentry environment - you don't need communication. The stresses on the nozzle will burn the niobium first, it'll show in the signature, even pulse if folding. Lots of other clues given composition analysis.

You more need RCS control authority and props/battery life. Could perhaps rearm destruct too and trigger on off nominal out of profile box as safety measure w/o ground track.

add:
Engine gimbals might also add coarse control authority although highly nonlinear. The models of effect will change greatly with  environment, but the first order effects induced chaos could be modulated by the RCS since they are delayed by a hundred microseconds or so.
« Last Edit: 05/08/2014 07:42 pm by Space Ghost 1962 »

Offline sheltonjr

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #27 on: 05/08/2014 06:33 pm »
The black boxes that I am familiar with.

Ruggedize memory surrounded with 2-3 inches of thermal insulation.   Encased in a steel body.  The conductors to the memory are designed to thermally fuse/disconnect so they no longer conduct heat to the memory.  A water activated pinger is external,  not sure it would survive reentry.

Offline Elmar Moelzer

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #28 on: 05/08/2014 06:44 pm »
The black boxes that I am familiar with.

Ruggedize memory surrounded with 2-3 inches of thermal insulation.   Encased in a steel body.  The conductors to the memory are designed to thermally fuse/disconnect so they no longer conduct heat to the memory.  A water activated pinger is external,  not sure it would survive reentry.
Well of course it would have to be built to match the needs of a reentering stage versus a crashed airplane.

Offline pagheca

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #29 on: 05/08/2014 06:44 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)

Let me remind that Elon Musk plans are to have everything recycled in a matter of hours. This, according to someone, means that you have enough stages ready to form a sort of "roaster" while the other stages are getting back to launch site, but this is not true. Maybe EM will change his mind, but according to what he said, he really meant "single-digit recycle time". And this is because he considers this the only strategy available to REALLY bring the cost of launches down. Organizing a transport from Australia to the US at any launch could make a relevant fraction of the overall cost for mission in HIS plan.

Please note I'm not debating if this is reasonable or not. I'm just reporting.

Online Llian Rhydderch

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #30 on: 05/08/2014 07:15 pm »
Hmm, what about a small eject able "black box" type of thing that stores the telemetry and is ejected the moment the stage breaks up. This could be triggered something like the launch abort type of trigger system. The data itself could probably fit on a micro SD card, or a combination of several (to provide redundancy), which are very small and lightweight. The bigger challenge might be to bring the thing down in one piece and the even bigger one would be finding it once it has landed, probably somewhere in the middle of the ocean. I am sure there are people on this board that have a better idea why this would or would not work (and what would be required to make it work).

What protects the black box?

Well, for early tests SpaceX might do on upper stages that are not expected to survive reentry, but for which they still desire to collect data on the first phase (high-altitude phase) of the test flight, they could make a variation on one of these:  Reentry Breakup Recorder.

I would imagine SpaceX could cobble together something like this, as a part of their test apparatus for second stage controlled descent tests, and pop it out of the top of the tank/interstage as they enter the thicker part of the atmosphere (but before rocket body breakup). 

I believe a box like that could collect a lot of data from the thermal sensors, attitude control, etc. and send it via short-distance telemetry to the "black box" that is designed to collect the data, and store and forward it to an aircraft monitoring the test somewhat later. 
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."

Online Llian Rhydderch

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #31 on: 05/08/2014 07:26 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)

Let me remind that Elon Musk plans are to have everything recycled in a matter of hours. This, according to someone, means that you have enough stages ready to form a sort of "roaster" while the other stages are getting back to launch site, but this is not true. Maybe EM will change his mind, but according to what he said, he really meant "single-digit recycle time". And this is because he considers this the only strategy available to REALLY bring the cost of launches down. Organizing a transport from Australia to the US at any launch could make a relevant fraction of the overall cost for mission in HIS plan.

Please note I'm not debating if this is reasonable or not. I'm just reporting.

I think your post may fit better in a different thread, downrange recovery, or rapid turnaround. 

This thread is limited in scope to the controlled-descent tests of F9 upper stages, and especially what might be learned from early tests, even before the stage is hardened to survive reentry.  Even after that, I would expect we will see all the tests for some time to be over-ocean tests, just like SpaceX is doing on the first stage controlled descent test program.

Until the very end of the test program, recovery isn't even in the cards. 
« Last Edit: 05/08/2014 07:28 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 Jim

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #32 on: 05/08/2014 07:49 pm »

I believe a box like that could collect a lot of data from the thermal sensors, attitude control, etc. and send it via short-distance telemetry to the "black box" that is designed to collect the data, and store and forward it to an aircraft monitoring the test somewhat later.

A.  The thermal sensors are not standard items, and so the stage would have to be set aside from normal production to install them.  That also goes for testing them and the data collection system

b.  So you are going to have this box transmit to an airplane?

Offline Elmar Moelzer

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #33 on: 05/08/2014 08:01 pm »

Well, for early tests SpaceX might do on upper stages that are not expected to survive reentry, but for which they still desire to collect data on the first phase (high-altitude phase) of the test flight, they could make a variation on one of these:  Reentry Breakup Recorder.

Ha! That is exactly what I had in mind! Great find!

Online Llian Rhydderch

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #34 on: 05/08/2014 08:18 pm »

I believe a box like that could collect a lot of data from the thermal sensors, attitude control, etc. and send it via short-distance telemetry to the "black box" that is designed to collect the data, and store and forward it to an aircraft monitoring the test somewhat later.

A.  The thermal sensors are not standard items, and so the stage would have to be set aside from normal production to install them.  That also goes for testing them and the data collection system

b.  So you are going to have this box transmit to an airplane?

Yep.  That is the point of this whole thread. 

Just like any flight test program requires investment of company funds to execute the test protocols and instrument the "object under test". 

And note, this is exactly like the existing controlled descent test program SpaceX is executing on the first stage booster over water tests.  They've invested private capital to design changes into the test vehicle (e.g., in-flight ignitors on the first stage engines, at least two test versions of nitrogen RCS thrusters, telemetry, sensors, avionics, computing, etc.) and they've invested in data acquistion (e..g., airplanes in the sky, ground links for part of the telemetry and radar acquisition, etc.), and the focus of a small team of engineers on the reentry (non-mission) part of the flight profile (new designs, new analysis, etc.).  It all takes money. 

It just happens that the base vehicle (unmodified flight stage) and the cost of putting it into the sky for the start of the test phase, is close to no cost.  The vehicles here were expendable, and were already going into the drink.

So we are looking at the delta-cost, the cost of turning an expendable stage into a post-mission test vehicle, and the cost of running the tests after the (successful) mission occurs.

Therefore, to your questions:

A) yes, there are, necessarily, changes to the stage to equip it to be a test vehicle

B) see the REBR article I linked to earlier.  It has been done before.  And either airplanes, or surface ships, or a satellite could collect the data from the REBR after data collection.  In fact, the first one floated on the ocean surface for a while, continuing to transmit.  But the plan is, I think, to collect the data after the plasma phase of the reentry and prior to splashdown.

So the point of the thread is that SpaceX might do the same thing on the second stages at some point.


Edit: fixed link
« Last Edit: 05/08/2014 08:22 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."

Online Llian Rhydderch

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #35 on: 05/08/2014 08:19 pm »

Well, for early tests SpaceX might do on upper stages that are not expected to survive reentry, but for which they still desire to collect data on the first phase (high-altitude phase) of the test flight, they could make a variation on one of these:  Reentry Breakup Recorder.

Ha! That is exactly what I had in mind! Great find!

Indeed.  When I read your thread, I got the sense that you were inventing this thing I had read about a few years ago.

Great invention!   :D
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 a_langwich

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #36 on: 05/08/2014 08:33 pm »

I believe a box like that could collect a lot of data from the thermal sensors, attitude control, etc. and send it via short-distance telemetry to the "black box" that is designed to collect the data, and store and forward it to an aircraft monitoring the test somewhat later.

A.  The thermal sensors are not standard items, and so the stage would have to be set aside from normal production to install them.  That also goes for testing them and the data collection system

b.  So you are going to have this box transmit to an airplane?

In the link the poster included, the REBR included thermal sensors and accelerometers and so on. 

But if SpaceX is planning to recover the second stage, and they want to include additional sensor data transmitted into the box and stored there, or other hardware, I imagine that would become part of normal production for a while, just as legs for the first stage were incorporated.

As for when it's transmitted, that wasn't clear to me from the article.  One survived the landing, floated (surprising for a black box type object, they must have had a flotation deployment mechanism?), and transmitted data from the surface of the ocean.  But it might also have transmitted in the lower atmosphere as well, on the way down.

This might have been mentioned earlier in the thread, but I'm sure SpaceX will be watching the inflatable decelerator test on the Cygnus module coming up very closely.  Maybe that will point to a new, more mass-efficient route.  Or maybe not.

Offline bfowler

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #37 on: 05/08/2014 08:46 pm »
What protects the black box?

What about something like the Stardust return vehicle? That looks about a meter in diameter, so probably even smaller.


And has small sample return not already been looked at in detail, with Russian VBK-Raduga, and the European PARES study?
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Online Llian Rhydderch

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Re: Falcon 9 upper stage controlled descent tests?
« Reply #38 on: 05/08/2014 09:04 pm »
What protects the black box?

What about something like the Stardust return vehicle? That looks about a meter in diameter, so probably even smaller.


And has small sample return not already been looked at in detail, with Russian VBK-Raduga, and the European PARES study?

This thread is not about small sample return.  There will be no samples involved.

It is about doing some test flights, and gathering data, and several of the posts above deal with ideas for collecting test data.  A few of those suggestions include designing data recorders that can survive reentry, and I believe Stardust was mentioned in that context, as it was a small vehicle designed to withstand atmospheric reentry.
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."

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