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

[Jakusb]

From Update thread:

Elon Musk @elonmusk
@alankerlin Hydraulics are usually closed, but that adds mass vs short acting open systems. F9 fins only work for 4 mins. We were ~10% off.

So this would imply that the Grid Fins froze about 24 seconds short of their required operating duration... Unless they locked them in a save position in time, this could have some strange effects, would it not?
With 50% more fluid, this would imply 120 seconds of more control (very roughly).. seems overkill, but better safe then sorry I guess. And some compensation for strong winds might require more maneuvering, I would assume..

[Robotbeat]

I don't think the first stage has any hydrazine. Pink coats? ...I think I'm missing some reference, here.

[Mongo62]

SpaceX has already done a great deal in furthering that goal, as you can see from whispers from Europe and ULA about reuse (where before there was mockery, at least from Europe).

There was mockery from ULA too. I still vividly remember an advertisement where they compared the sound of ULA (a photo of a rocket launch) with the sound of SpaceX (a photo of a microphone).

Admittedly, the ULA mockery was not specifically about reuse, it was more about their slow launch rate compared to their press announcements.

But I notice that I'm not seeing any more of that type of advertisement from ULA these days.

[edkyle99]

I don't think the first stage has any hydrazine. Pink coats? ...I think I'm missing some reference, here.

It refers to the images of crowds gathering around the remains of the first stage from the most recent Chang Zheng launch by China.

 - Ed Kyle

[savuporo]

I don't think the first stage has any hydrazine. Pink coats? ...I think I'm missing some reference, here.

FY-2G launch just a short week or so ago. they also recovered what seemed like largely intact first stage - tho I'm sure they would prefer not to.

[hrissan]

From Update thread:

Elon Musk @elonmusk
@alankerlin Hydraulics are usually closed, but that adds mass vs short acting open systems. F9 fins only work for 4 mins. We were ~10% off.

So this would imply that the Grid Fins froze about 24 seconds short of their required operating duration... Unless they locked them in a save position in time, this could have some strange effects, would it not?
With 50% more fluid, this would imply 120 seconds of more control (very roughly).. seems overkill, but better safe then sorry I guess. And some compensation for strong winds might require more maneuvering, I would assume..

I'm afraid the fins froze in some awkward positions remaining rather rigid, so worse than not having it at all.

While the computer might be programmed to deal with a stuck fin (probably has input on actual fin positions)

Finding landing solution with all fins stuck may be impossible, so it did what it could compensating forces rotating stage or pushing it sideways with engine vectoring and rather weak cold gas thrusters.

No wonder the stage crash landed... Actual control commands sent by computer during the final seconds is the most interesting thing I'd like to lay my greedy hands on.

P.S. If SpaceX predicted the loss of fluid, then there might be some sensor and computer could fold fins in good position just before the complete loss (and thus allowing for soft landing in some random place close to the pad), I just have no idea how many possible failure modes have some descent programmed responses.

[Robotbeat]

SpaceX has already done a great deal in furthering that goal, as you can see from whispers from Europe and ULA about reuse (where before there was mockery, at least from Europe).

There was mockery from ULA too. I still vividly remember an advertisement where they compared the sound of ULA (a photo of a rocket launch) with the sound of SpaceX (a photo of a microphone).

Admittedly, the ULA mockery was not specifically about reuse, it was more about their slow launch rate compared to their press announcements.

But I notice that I'm not seeing any more of that type of advertisement from ULA these days.

That wasn't ULA, it was actually PWR:
http://www.wehatesheep.com/media/uploads/pwr_smokefire_reprint_wo_utc_lightbox_detail.jpg

... Of course, "PWR" doesn't exist since they merged with Aerojet to become Aerojet Rocketdyne. I guess that's Karma...

[meekGee]

From Elon

@elonmusk: Didn't get good landing/impact video. Pitch dark and foggy. Will piece it together from telemetry and ... actual pieces.

Another explosion, another missing video.  What are the odds? 

But I see these landing experiments as an interesting side-show.  The real news continues to be the repetitive success of this launch vehicle.

 - Ed Kyle

Opinions vary...

Rockets have launched successfully before, so IMO the real news is that most everything regarding reusability worked to plan, reentry and atmospheric flights down from hypersonic went well, and the failure is well understood and trivial.

Also, I'm glad the mission was successful. 

[Robotbeat]

Success is going to be so, so sweet when it finally comes sometime in the next few months.

[Ronpur50]

Just out of curiosity, have we heard anything on the health of the Dragon in orbit?  No problems?

[rickl]

When SpaceX first announced that they were going to try to boost back and land the first stage, I assumed that the first few attempts would break up at high speed and high altitude.  I was amazed that they achieved that part on the very first try with the CASSIOPE flight.  So I'm delighted with their progress so far.

[Will]

From Elon

@elonmusk: Didn't get good landing/impact video. Pitch dark and foggy. Will piece it together from telemetry and ... actual pieces.

Another explosion, another missing video.  What are the odds? 

But I see these landing experiments as an interesting side-show.  The real news continues to be the repetitive success of this launch vehicle.

 - Ed Kyle

What Ed said. "It was pitch dark" Except for the blazing rocket engine. Which cranks out a lot of lumens.

[cro-magnon gramps]

Success is going to be so, so sweet when it finally comes sometime in the next few months.

I heard Jackie Gleason in your voice just then, "Hoow... SWEET IT IS!!"

[Space Pete]

They'll get there eventually, of that I have no doubt.

[savuporo]

Just out of curiosity, have we heard anything on the health of the Dragon in orbit?  No problems?

What an unpopular question .. who cares about space here, it's all about rockets

http://spaceflightnow.com/2015/01/05/spacex-5-mission-status-center/

The early hours of the Dragon cargo craft's flight to the International Space Station are going as planned, according to SpaceX.

The guidance, navigation, and control systems door has been opened, SpaceX says. The instruments inside the navigation bay can now be activated and tested.

The spaceship's rendezvous with the space station began with this morning's launch, but major maneuvers to guide Dragon closer to the orbiting research complex will begin early Sunday. A series of burns using the craft's Draco thrusters will re-shape Dragon's orbit to match that of the space station.

Early Monday, the space station and Dragon will be close enough to establish radio communications before the robotic space freighter begins its final approach from below the laboratory.

Capture with the space station's robotic arm is expected around 6:12 a.m. EST (1112 GMT) Monday. Space station commander Butch Wilmore will be at the controls of the robot arm for Dragon's arriva

[MP99]

Hydraulic fluid doesn't get used up unless there's a leak.

Or unless they decided to used an open system in which the hydraulic fluid is simply dumped downstream of the actuator, which makes for a simpler system and eliminates the mass of a collection tank and associated plumbing.

And will get you the opportunity to explain yourself to the EPA.

From what I've just read on open hydraulic systems, they are called "open" because they return the fluid to a tank instead of the fluid remaining in a closed pressurized loop. So from a pollution viewpoint, open and closed systems appear identical to me.

I doubt it's practical, but would be neat if the fins could run on a reservoir of RP1 (from the interstage), then dump into the fuel tank for the landing burn.

Downside - need more pressurant to overcome the pressure of the prop tank.

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

Cheers, Martin

[Remes]

Hydraulic fluid doesn't get used up unless there's a leak.

Or unless they decided to used an open system in which the hydraulic fluid is simply dumped downstream of the actuator, which makes for a simpler system and eliminates the mass of a collection tank and associated plumbing.

And will get you the opportunity to explain yourself to the EPA.

From what I've just read on open hydraulic systems, they are called "open" because they return the fluid to a tank instead of the fluid remaining in a closed pressurized loop. So from a pollution viewpoint, open and closed systems appear identical to me.

The problem with a hydraulic tank is sloshing and the risk of sucking air into the system. Especeally if you a have a fancy thing like flyback with free floating phases.

The Ariane 5 (if I'm not completely wrong) uses for booster and EPC a hydraulic blow down system. There is not much on the net, but here, the second picture on the left side:

http://www.b14643.de/Spacerockets_1/West_Europe/Ariane-5/Gallery/EAP.htm

The two lengthy bottles are the reservoir (Groupe d'Activation Tuyere GAT). 200 litres of oil, under 380bar helium pressure. Similar concept for EPC.

Here is even more:
http://www.capcomespace.net/dossiers/espace_europeen/ariane/ariane5/caracteristiques.htm
http://www.capcomespace.net/dossiers/espace_europeen/ariane/ariane5/EPC%20vulcain%20GAM.jpg
http://www.capcomespace.net/dossiers/espace_europeen/ariane/ariane5/EAP%20systeme%20GAT.jpg

Rocket hydraulics tend to be open, from what I can tell.

I remember the RD-170 has a fuel-pressure to hydraulic pressure converter. I would guess the RD-180 is similar. Shuttle had a closed system on every actuator (SSME TVC, SSRB TVC, and all the rudder and other moving stuff). From what I can tell I would rather tell the opposite.

[CJ]

What Ed said. "It was pitch dark" Except for the blazing rocket engine. Which cranks out a lot of lumens.

I offer no opinion on whether or not good vid of the landing attempt exists, but I can offer some experience in shooting night video with plenty of illumination; I had to shoot some video of a car accident at the request of the driver involved (no one was injured, but fault was in contention).  It was raining that night, and, being night, it was dark (funny how that works...).

The scene was very wel lit by road flares. I could see just fine. Camera, however, have less ability than the human eye when it comes to mixed lighting conditions, and I ended up with mainly shots showing brilliant flares against black.

I therefor think it's possible (based on my experience, as well as the vid from last night's launch) that the landing vid shows the Merlin plume just fine... but pretty much only that, as the rest of the shot is washed out by the light source. Just a guess on my part.



On to the core issue, the core recovery attempt itself; I'm indeed sorry that the landing attempt wasn't fully successful, though the result was not a surprise; I've said before that with so many aspects only modeled, there were a lot of ways reality could bite them. Looks like one did.

However, though the landing didn't fully succeed, the attempt itself mostly did; it looks as if the F9 made it almost all the way, and if so, the entire flight regime from stage sep to just before touchdown is "in the can" rather than relying in some areas on modeling. The part that's left looks to be within the envelope already tested by the grasshoppers.
 
So, based on the results of this flight (only the bits we know now, of course) I'm changing my estimate. I originally thought it would take three or four attempts before a landing succeeded.  I now think the odds of fully succeeding on the next flight are better than 50-50.


 

[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

[Rocket Science]

This is an engineering experiment thus all test results are valid, no subjectivity required... Even if or when a landing is achieved economic reusability will remain to be proven.  As always I will keep an open mind and commend them for attempting something new regardless of the outcome...