LIVE: SpaceX Falcon 1 Launch 5 (RazakSat) - July 13/14

[butters]

Flight 2 failure was caused by LOX sloshing and mitigated by tank baffle modifications.  The wobble was much much worse than on flights 4 or 5. 

The remaining wobble may be an indication that the baffle still needs a bit of fine-tuning.  Or maybe its just needs some tuning of the control algorithms.

Assuming the final orbit really was close to a bullseye as Musk claimed, the F1 guidance system in its current state seems to be quite capable of satisfying customer requirements given a similar payload mass margin.

For every satisfied customer, they get a new set of telemetry data to help refine their algorithms and allow for tighter margins.  As they establish reliability, they can begin to optimize performance.  Reliability is obviously the top priority.

[Jim]

1.  Is this relatively unique and contributes to the apparent control response issues?
2.  How does the F1 second stage flight response compare to a LV with a solid upperstage motor?

1.  no, it is SOP.

2.  Pegasus and Taurus are smooth.

[butters]

As far as I can tell, the F1 second stage only seems to use the Kestrel for adjustment during second stage burns and not any secondary thrusters.

F1 second stage has a single pressure-fed engine.  Kestrel gimbals for pitch and yaw control, but attitude thrusters are required for roll control.

[yg1968]

I have posted the video of the entire webcast here:

http://forum.nasaspaceflight.com/index.php?topic=17815.msg436491

[William Barton]

1.  Is this relatively unique and contributes to the apparent control response issues?
2.  How does the F1 second stage flight response compare to a LV with a solid upperstage motor?

1.  no, it is SOP.

2.  Pegasus and Taurus are smooth.

Is there a solid motor size below which TO is negligible?

[ugordan]

2.  Pegasus and Taurus are smooth.

Is there a solid motor size below which TO is negligible?

I believe "smooth" in this context was referring to attitude stability, not vibrational environment. Pegasus and Taurus have solid stages so no propellant sloshing and consequently no wobble.

[kkattula]

SpaceX have linked the U-Tube video on their website.

I wonder if their publicity department may be a little busy preparing stuff for the Augustine Commission or something?  Fair enough if they are.


Congrats & much appreciation for letting us watch anyway.

Can't wait for Falcon 9.

[stockman]

well.. .Thank you to yg1968  for the video post (hopefully spacex will provide a higher def version again like they did with the last flight - hint hint... )

I slowed down the video during stage separation and to my eye it all appeared nominal - no contact with the engine bell that I can see... It looks like a narrow fit but it seemed to come apart clean

Here are a few pictures of the sequence in question... Hope it is not too many - I just wanted to show the sequence...

[stockman]

[stockman]

[stockman]

[stockman]

Last ones..

[nooneofconsequence]

@ Jim

Let's look at this from a slightly different perspective.  I don't think anyone doubts that Falcon-1 wiggles around during MECO, first stage jettison and second stage engine ignition and even noticably at SECO.  The important question is how important is this?

If it were a max payload mission, it have implications.  The performance is lost with this wiggles

Only matters if its intrinsic to the design. No one expects/uses/relies on max performance in the early development cycle of a LV.

May I suggest we quantify such characteristics and see if Space-X's development processes can refine the design - I think most of this is immature GNC software that needs more flight experience rather than a flawed design.

Don't think F1e and Pegasus/Taurus I are excellent comparisons - a soild second stage is much simpler. Orbital and Space-X get about the same kudo's at the early stages - Orbital being the more steady dependable turtle to Space-X 's flashy, flamboyant, over the top speed and goals. Interesting contrast - both are enjoyable to watch.

[edkyle99]

Here's an on-board video of an Ariane 5 launch.  Notice the horizon "wiggling" as the ascent proceeds, about 3:30-4:00 and later into the video.   



I'm going to look for some comparable on-board Centaur and Delta upper stage video.

 - Ed Kyle

[stockman]

Here's an on-board video of an Ariane 5 launch.  Notice the horizon "wiggling" as the ascent proceeds, about 3:30-4:00 and later into the video.   


I'm going to look for some comparable on-board Centaur and Delta upper stage video.

 - Ed Kyle

Good find Ed... Next to that the Falcon looks rock steady.... I think even the shuttle stack has some wiggle to it (I seem to recall people mentioning it in the STS125 launch from the Tank perspective). Not as much but definitely it occurs..

[Jim]

... I think even the shuttle stack has some wiggle to it (I seem to recall people mentioning it in the STS125 launch from the Tank perspective). 

That was the vehicle flexing

[ugordan]

Actually, that sporadic rolling motion of the Ariane first stage seems like an intentional thing to me - maybe a thermal constraint roll or something. I didn't notice any significant wobbling Ed speaks of.

Slightly related to that - inaugural Atlas V launch, video after 6:00 shows noticeable RL-10 gimballing. Hard to judge from two different cameras and FOVs, but I'd say more gimballing than Kestrel for most of the flight. By the same token that affects performance, does it not?

[stockman]

... I think even the shuttle stack has some wiggle to it (I seem to recall people mentioning it in the STS125 launch from the Tank perspective). 

That was the vehicle flexing

The flexing I remember Jim.. I will have to dig into it when I am home tonight but I seem to recall there was some obvious correction right after SRB sep... More obvious last launch than before....

[Jim]

Here's an on-board video of an Ariane 5 launch.  Notice the horizon "wiggling" as the ascent proceeds, about 3:30-4:00 and later into the video.   

Most of that is a roll rate

[Jim]

 I will have to dig into it when I am home tonight but I seem to recall there was some obvious correction right after SRB sep...

That is not the issue.  the issue is the rocking or wiggling back and forth