SpaceX Falcon 9 v1.1 - Dragon - CRS-5/SpX-5 -Jan. 10, 2015 - DISCUSSION

[Jim]

Seeing as the FAA is (likely) going to be more involved in approval of any future fly-back attempts, does anyone know if:

1) SpX has/plan to have a 'black box' somewhere on the 1st Stage or would the flight computer(s) provide that info if req'd?
1a) Are they hardened enough to survive a legit crash/explosion?
2) Is/will that even be required?
2a) Do UAS's (drones) have them? I think they do.
3) Is a transponder required on the 1st stage?

I think they're on the cusp!! Getting excited.

Thanks,
Splinter

1.  The data is transmitted.  That is what telemetry is.   Some might be recorded.
1a.   see #1
2. see #1
2a.  doesn't matter
3.  That is part of the range safety system.  The system update will be to transmit GPS data eliminating the need for a transponder

[robertross]

As to this talk of open vs. closed hydraulics:

There are actually many variants, so it's important to get the context correct.

Open 'loop' (hydraulics) is the fluid coming from a reservoir (typically vented to atmosphere, but it could be pressurized, typically with air for low pressures or Nitrogen for higher pressures and to keep the fluid 'dry') and is then delivered via a pumping device to deliver flow to the control valves and/or actuators. The returning fluid is fed back to the reservoir to be re-used.

Closed 'loop' (hydraulics) is the fluid kept in the loop, typically between a pump & actuator (typically a motor). It is only when the actuator is moved that the fluid in the loop moves within that loop. Of course typical hydraulic closed loop systems utilize a small pump to dump oil into the lower pressure of the two sides of the loop (after the work is done, from the motor for instance). And for what is allowed into the loop has to have an equal amount dumped out, and is usually handled by a valve, and is typically cooled & filtered. Properly designed, just the cooler itself could be used to hold the fluid required due to expansion & contraction.

Now the rocket would have to have a closed 'system' (so no fluid escapes), but it also must have either a pump driven by some means to deliver this flow, or it has an accumulator to store the fluid under pressure (think of a water pump & tank on a well system in a house). The tank (accumulator) has to have a pressurant gas (Nitrogen typically for hydraulics to prevent explosion due to hydrocarbons present) at a pressure just under that required to operate the system's actuators. Now if there is no pump in the system (external turbopump or similar driven off a shaft or via hot gases, or an electric pump with a battery), you have to rely totally on the size of the accumulator (tank) to supply that fluid. This fluid typically passes through a pressure reducing valve to drop the pressure to somthing more usable, plus it allows a higher charge pressure in the accumulator to lengthen the amount of time to operate the hydraulics. Once the pressure drops off below the setting of the reducing valve & the minimum that is required to run the actuators, they cease to work effectively.

Although it adds weight, the simplest way to boost the amount of time available to operate hydraulics in this manner (if it is indeed how the system works) is to add more accumulators, or make the existing one(s) larger. Increasing the pressure in the accumulator is possible (gas side) but it requires a stronger tank, and likely a new pressure reducing valve that can handle the higher initial pressure.

Now they can also have the accumulators charged with Helium, and with the propellant tanks also using this gas, if they had an auxilliary bottle on board, they could supplement it with that.

[Kabloona]

Robertross, thanks for that summary. You might want to post it over here where there is a thread specifically on the subject:

http://forum.nasaspaceflight.com/index.php?topic=36536.0

However, Robotbeat has stated (I assume he has a source) that the hydraulic fluid is simply dumped overboard. See his post in the thread link above.

[swervin]

Seeing as the FAA is (likely) going to be more involved in approval of any future fly-back attempts, does anyone know if:

1) SpX has/plan to have a 'black box' somewhere on the 1st Stage or would the flight computer(s) provide that info if req'd?
1a) Are they hardened enough to survive a legit crash/explosion?
2) Is/will that even be required?
2a) Do UAS's (drones) have them? I think they do.
3) Is a transponder required on the 1st stage?

I think they're on the cusp!! Getting excited.

Thanks,
Splinter

1.  The data is transmitted.  That is what telemetry is.   Some might be recorded.
1a.   see #1
2. see #1
2a.  doesn't matter
3.  That is part of the range safety system.  The system update will be to transmit GPS data eliminating the need for a transponder

Thanks for the quick reply, Jim!

I guess I envision a non-perfect world of TM dropping out, but then I guess the FTS would have a roll to play if that occurs? -- in which case a 'black box' of sorts would be handy to find during recovery with data physically stored on it. I've never seen TM drop off, so I guess you haven't either..... (sarcasm) haha ;-)

If only the rest of the FAA agreed with your assertion on GPS vs transponders for position reporting. They're getting there, but not yet.

We find ourselves in an interesting world where the FAA is doing more than posting TFR's and re-routing civilian flights for the rice-bowl domain of the rocket business/engineers WRT to F9 RTLS; that's where my questions came from.

Cheers,
Splinter

[mlindner]

The landing could have failed in at least three ways.

1. Grid fins froze in a non neutral position, putting the stage out of control at the last moment.
2. Lack of grid fins movement resulted in excess need for gimballing and nitrogen thrusters. Perhaps resulting in rocket being at an angle while attempting to maintain course, resulting in landing on 1-2 legs first, buckling structure.
3. Reduced control authority resulted in hitting ground equipment.
Add your own.... we will probably know in a couple days....

Or most likely, loss of hydraulic fluid resulted in non-functioning fins resulting in a control loop that expects response when input is given but no response is returned. The lack of response will greatly destabilize the system and the result could be any number of odd pitches, yaws, rolls, or translations based on the position the fins were in and how the feedback response is measured.

Anything you can surmise beyond this is pure guessing (not even estimated guessing) because you have no information to determine a conclusion.

[jiffylube84]

I live about 120 miles from the Cape on the Gulf Coast I was able to see the launch and the 1st stage relight when it did you could see a light colored cloud right below the glow from the engine for a few seconds it was pretty cool I tried to get some pictures but unfortunately I have a streetlight by my house and it didn't turn out. I was pretty bummed out when the shuttle quit flying because there was nothing that compared to the beauty of a shuttle launch but with all the events that happen with the Falcon9 launch it is a close second atlas and deltas don't compare. Spacex is getting me excited about launches agian. What caused that cloud under the 1st stage when it fired the second time I thought it was exo atmospheric at that point?

[JohnWT]

What I think we do not know is the stability of the ASDS versus the capacity of the legs and rocket to absorb any discrepancies in velocity and angle at the point of contact.  If the deck is stationary or descending then potentially the rocket can match its position and velocity at the point of contact.  But even this is more complex than the grasshopper landings - zero velocity and vertical at zero altitude.  If the deck is ascending then some degree of hard contact is inevitable as in order to match an ascending velocity the rocket would have to go below the altitude of zero velocity.

[guckyfan]

Now they can also have the accumulators charged with Helium, and with the propellant tanks also using this gas, if they had an auxilliary bottle on board, they could supplement it with that.

They do have a handy nitrogen source. With the grid fins active they need a lot less cold gas thrusters action. My guess would be they use that gas for pressurant. Actually I thought about He before but while reading your post I remembered that pressurized nitrogen is sitting right in the interstage.

[ChrisWilson68]

Especially on these NASA missions I have my doubts they will be allowed to scrub a launch for something that will not be a danger to the actual mission.

Allowed?  SpaceX can scrub for any reason they want to.  They can scrub because Elon isn't feeling lucky that day.

Annoying your customer isn't a good idea, though, so if they scrub too often for reasons NASA doesn't like (or even if they scrub too often for reasons NASA is fine with, like replacing valves), it will impact their likelihood of getting follow-on NASA business.

[Hauerg]

Has to be the first "crash landing" that puts a smile on my face.

(I did not believe they would make physical contact with the ship at first try.)

Congratulations!

[Star One]

Disappointed by the media coverage of this at least in the UK which has empathised the perceived failure over the actual successes.

Just thinking I bet they wouldn't be allowed to tinker around with reusability if they were flying a national security payload.

[gingerscot]

Yeh I agree with the UK media coverage.  BBC first had headlines of "SpaceX Failure" and then changed it to "crash" but the article still comes across as emphasising the failure unless you read further down.

I suppose with the instantaneous fixed launched windows SpaceX had no choice with the lack of daylight and weather conditions at the barge site however wondering if the weather conditions at the barge site could effect the timings of a non-ISS launch to improve their chances.

[mfck]

Yeh I agree with the UK media coverage.  BBC first had headlines of "SpaceX Failure" and then changed it to "crash" but the article still comes across as emphasising the failure unless you read further down.

I suppose with the instantaneous fixed launched windows SpaceX had no choice with the lack of daylight and weather conditions at the barge site however wondering if the weather conditions at the barge site could effect the timings of a non-ISS launch to improve their chances.

I doubt either the weather, which was quite benign, or the lighting conditions had anything to do with the hard landing.

Edit: both are conditions they need to accommodate, not to avoid by moving the launch schedule

[ChrisWilson68]

I really like the idea of the ram air device as used in aircraft emergencies.

The grid fins are first deployed in vacuum.  No ram air.  And they need to work while the stage is travelling through atmosphere at speeds from hypersonic through subsonic.  That would be quite a bit more demanding than a typical aircraft ram air system.

[ChrisWilson68]

So pushing the nozzle around with high pressure RP1 makes a lot of sense.  Trying to plumb high pressure RP1 all the way through the RP1 and LOX tanks up to the interstage... not so much.

Plus, you only have the high pressure RP1 when the turbopump is running, which only happens when the engine is firing.  The grid fins have to work between burns.

[Mapperuo]

Yeh I agree with the UK media coverage.  BBC first had headlines of "SpaceX Failure" and then changed it to "crash" but the article still comes across as emphasising the failure unless you read further down.

I suppose with the instantaneous fixed launched windows SpaceX had no choice with the lack of daylight and weather conditions at the barge site however wondering if the weather conditions at the barge site could effect the timings of a non-ISS launch to improve their chances.

The UK coverage was awful, Sky News thought the first stage didn't land for a month after launch, confusing it with  Dragon.

[Karloss12]

Yeh I agree with the UK media coverage.  BBC first had headlines of "SpaceX Failure" and then changed it to "crash" but the article still comes across as emphasising the failure unless you read further down.

BBC doesn't have a clue about SpaceX.  When F9R-D1 exploded, the BBC headline was "Falcon 9 Rocket Explodes".  When I e-mailed BBC to explain that it was not a F9 rocket as it was absent of much of its safety systems and engines and it was a reussability "test" they improved the headline slightly to "Falcon 9 Rocket Explodes during test".

And the BBC Science Correspondent seems to be very over worked or uninterested in aerospace as he seems to rely allot on advise from old space experts for his blogs.  According to him it is going to be a challenge convincing customers to launch their satellites on a second hand rocket.  Given the choice between catching a airliner flight on an aircraft that has rolled straight out of the workshop or has been in service for 6 months, I think the choice is simple.

[gingerscot]

Yeh I agree with the UK media coverage.  BBC first had headlines of "SpaceX Failure" and then changed it to "crash" but the article still comes across as emphasising the failure unless you read further down.

I suppose with the instantaneous fixed launched windows SpaceX had no choice with the lack of daylight and weather conditions at the barge site however wondering if the weather conditions at the barge site could effect the timings of a non-ISS launch to improve their chances.

I doubt either the weather, which was quite benign, or the lighting conditions had anything to do with the hard landing

Edit: both are conditions they need to accommodate, not to avoid by moving the launch schedule

I'm sure I remember someone saying there were 30kn crosswinds(?) which can't have helped the final few seconds.  Even if the barge was clever enough to compensate for a steady level a sudden increase in wind would have some effect. 

Did any of the grasshopper tests involve anything but benign conditions? Lighting conditions maybe irrelevant bar better viewing from afar I admit.   

[rpapo]

Did any of the grasshopper tests involve anything but benign conditions? Lighting conditions maybe irrelevant bar better viewing from afar I admit.

One of the GH1 tests involved a relatively strong crosswind, but it wasn't gusty nor did it appear to vary much by height.  I say "much" because all crosswinds vary by altitude, though usually they are stronger as you go higher.

[Chris Bergin]

Yeh I agree with the UK media coverage.  BBC first had headlines of "SpaceX Failure" and then changed it to "crash" but the article still comes across as emphasising the failure unless you read further down.

I suppose with the instantaneous fixed launched windows SpaceX had no choice with the lack of daylight and weather conditions at the barge site however wondering if the weather conditions at the barge site could effect the timings of a non-ISS launch to improve their chances.

The UK coverage was awful, Sky News thought the first stage didn't land for a month after launch, confusing it with  Dragon.

I'm surprised I didn't see Kay Burley on a boat trying to force the barge into an exclusive interview.