LIVE: SpaceX - Falcon I (Mk.II) NET March 20 (Attempt 2)

[JonSBerndt]

charlieb - 21/3/2007  8:55 AM
At the altitude of separation we noted - there would be little aerodynamics at that point ...

That's probably  true, but it would still be interesting to know what qbar was at the time ...

charlieb - 21/3/2007  8:55 AM
As I suggested late last evening - sep motors need to be attached to either the second or first stage (or both maybe) to force a fast and cleaner separation from the stages..It's a simple, elegant - and well proven method.  A little extra weight to make a safer and more reliable launcher is cheap insurance.

I believe (based on info from the SpaceX web site) that there are cold-gas jets on the upper stage that perform attitude control during the coast phase between stages as well as acting as ullage motors to settle propellant (and separate the stages?).

Jon

[lmike]

So, we still don't know what a successful Falcon 1 launch would cost.

[meiza]

aero313 - 21/3/2007  2:59 PM

charlieb - 21/3/2007  9:55 AM
As I suggested late last evening - sep motors need to be attached to either the second or first stage (or both maybe) to force a fast and cleaner separation from the stages..It's a simple, elegant - and well proven method.  A little extra weight to make a safer and more reliable launcher is cheap insurance.

They also add cost and reduce reliability.  Every part you add to the vehicle (expecially energetics) requires purchasing, installation labor, checkout, etc.  In addition if you're talking about solid propellant sep motors, there's a new safety hazard that complicates ops.  Lots of vehicles separate with springs or even just a hot fire of the upper stage.  The bigger concern to me is the individual sep nuts that might have timing issues (but it worked in the simulation...)

I think one of the design philosophies used in Falcon I was trying to keep it as pyro free as possible. The fairing uses springs etc... There are sep/ullage helium thrusters in the second stage (They seem to be affiliated with roll control too?).
I don't know the exact separation mechanism but I think it's mechanical, no explosive bolts or anything like that.

[meiza]

This youtube video shows the serious complete roll (with bad precession too) of the second stage at 5:01-5:14 when it cuts off:

[nacnud]

Danderman - 21/3/2007  2:51 PM

DaveS - 21/3/2007  5:57 AM  And for you who doubts that the stage rolled before LOS: Watch the video again and this time keep a close eye on the horizon. Initially, it's diagonal but towards the end it goes vertical.  The only attitude change that have this effect, is a roll attitude change.

You are correct, at the end of the video there is finally a true roll. But, it doesn't seem to be rolling at a very high rate, certainly not a high enough rate to cut off telemetry.

Watch the YouTube footage, the extra 15 seconds of footage really show an increased roll.

[meiza]

If the second stage helium ullage/roll thrusters didn't work right or were damaged in separation, that would explain the bad separation and roll control problems later in the flight.

[kevin-rf]

If as some have suggested it was a stuck cold gas thruster. I wonder if condensation from that tropical air flash freezing inside a valve on climb out. We did see several large I assume frost flakes peel off during powered second stage flight. SpaceX has said nothing to date about N2 purging the interstage and payload to prevent ice from building up in unwanted spaces as the air pressure drops in the confined spaces.

[charlieb]

Generally - solid sep motors work all of the time.  With dual NSI's each - reliability is a virtual non-issue as long as the pryo power supply is functional. Solid based sep motors  have been used for decades  - especially on manned launchers (Saturn's IV-B, -V) - and are still used today.  They have the necessary ISP AND reliability to get the job done - vice a cold gas system that has little isp - great for gentle roll control - but little more than that.  Get a gas leak going uphill and you are hosed.

So- bolt 3 of them on the velocity forward end of the first stage - 120 deg apart, give each dual NSI's, a proven pyro power supply and you are all set.  

SpaceX is darn lucky that the second stage nozzle wasn't ripped right off it's thrust chamber housing IMHO. If the nozzle had RP-2 or LOX based cooling lines that formed the nozzle like a SSME or RL-10 (vice prop film cooled thrust chamber and radiation colled nozzle it has)- it would have been all over. It made interesting and informative video tho...

[bigdog]

Was not able to watch the launch, wow it looks like I missed a lot.  I'm still looking over the video from the links in a couple of places and reading all the posts has taken some time but My take so far is SpaceX has made a great second effort.  Too bad it didn't go all the way but congrats just the same.

[Analyst]

I don’t share the enthusiasm, the 95+% success. This has been a failure, period. If this has been any other vehicle, everyone here would call it a failure, and right so. All other is spin (or roll ) The vehicle did not reach any orbit, let alone the targeted one. About five minutes into an almost ten minute flight means you have less than half the velocity to orbit the earth. This is not “late in the second stage burn”, it is early and it started pretty soon into the burn. They never ended up in the Atlantic, probably the second stage crashed about 500 to 1000 km downrange, apogee doesn’t count. Sounding rockets go 300 km up and come down right away.

If we want to measure partial success (Hello Ed ), this second flight has been better than the first, no doubt an improvement, lets say 40% vs. 10%. First stage flight seems nominal, stageing has not been clean, and there has been a control problem, eighter because of the off-nominal staging or independent from it. Therefore probably two problems to deal with, or more if you count the “engine ring”.

This is a long way to go for Falcon 1. And Falcon 5 or 9 are much more complex, multiple engines with multiple control problems, ground support etc. I wish them success. But I hope people will be more realistic when claiming Musk and Bigelow will be on the moon by 201x.

The second Delta III did reach orbit, AC-2 was successful after the F-1 failure, as was Ariane 502. If we measure partial success, I say Delta IVH was at about 90%, it did reach orbit and had 3 upper stage burns and ended in a lower than planned orbit.

Analyst

PS: Have the two launches been (partially) paid by the government, the evil one that also buys Boeing and LM? This makes it less start up and risky and more like let the tax payer carry at least some costs and risk. This is a litte strange after all the bashing by Musk in the past.

[aero313]

charlieb - 21/3/2007  10:20 AM
Generally - solid sep motors work all of the time.

No argument, but it is still a cost/benefit trade.  Again, the cost/weight of the hardware isn't the only issue.  You'd be adding a new pyro system with increased costs due to safety and integration effort.  My rule of thumb is if you can make an existing system do a job, don't add another one.  That's how you hold down cost.  On the other hand, if SpaceX is using non-explosive sep nuts on their stage sep, that's a problem.  The variability in actuation time for these devices is large and can easily cause a tipoff at sep.

[aero313]

Analyst - 21/3/2007  10:31 AM

PS: Have the two launches been (partially) paid by the government, the evil one that also buys Boeing and LM? This makes it less start up and risky and more like let the tax payer carry at least some costs and risk. This is a litte strange after all the bashing by Musk in the past.

Yes, DARPA paid for both launches, but only the recurring cost of the launch, not the development costs.  NOTE TO ALL:  This is EXCACLTY the situation with Pegasus, where Orbital funded the development privately and DARPA paid $6M each for the first two launches.

[bigdog]

Okay I don't know what Elon saw in that video but I see a major control problem and it's not with roll.  From a few seconds after engine ignition of the second stage until the end there is increasing magnitude pitch and yaw movement.  You don't see roll of any magnitude until the end.  Remember they had the issue before the first static fire with an actautor and subsiquently replaced TVC boards.  I wonder if they over compensated for something and did they change guidance software too.  I hope they were able to get at least intermitent telemetry as it lost control so they have more data to look at.

Also I have to agree with most people here that the engine did contact the first stage and I don't think it was just a glancing blow.

[Avron]

Something causes the Yaw on the Second stage prior to it emerging from the first stage.. there is contact on the first stage, but one would expect the yaw to be countered and that it yaw back the other way, away from the contact point.. but it does not... so what is holding the stages together opposite to the camera?  Now look at the motion of the first stage.. it rotates in Yaw in the opposite way to the second .. but not counter to the point of collision... . attached images just shows the amount of miss alighnment that happens in less than 3 secs..

[bigdog]

McDew - 21/3/2007  6:49 AM

This was the most impressive DEMO launch I have ever watched.

More impressive than Delta IV Heavy Demo?

Better than big fireball at engine start?  Video of strap-on separation, ss nozzle deployment, fairing sep, payload?  I'm glad they had video but pretty middle of the road compared to other launches.

[Danderman]

nacnud - 21/3/2007  7:15 AM  Watch the YouTube footage, the extra 15 seconds of footage really show an increased roll.

Where did these extra 15 seconds come from?

 

 

[SimonShuttle]

Danderman - 21/3/2007  10:00 AM
Where did these extra 15 seconds come from?

Do you honestly believe someone is going to be able to answer that?  :laugh:  :laugh:  

[Skyrocket]

Avron - 21/3/2007  4:42 PM

Something causes the Yaw on the Second stage prior to it emerging from the first stage.. there is contact on the first stage, but one would expect the yaw to be countered and that it yaw back the other way, away from the contact point.. but it does not... so what is holding the stages together opposite to the camera?

I do not think, that something is holding the stages together. To my impression, it is more like a stuck attitude thruster, which starts yawing the upperstage immediately after seperation, casusing the upper stage to bump its nozzle against the interstage, which stops the motion. The yaw motion then starts immediately again in the same direction, hinting, that the attitude thruster is still thrusting. After ignition of the Kestrel engine, the stage gains control back over the yaw movement.

[bigdog]

tedcraft - 21/3/2007  5:39 AM

Congrats to SpaceX on as far as they got.  It was impressive they launched the same day they had a pad abort.

That they actually were allowed to recycle after an engine start is very impressive.  I doubt the East or West Coast Rage would allow that at the Cape or VAFB.  Having done so will give SpaceX good ammunition to convice them otherwise, will interesting to see how it develops.

Assuming the 2nd stage shut down with a loss of control at about 315 seconds, the inertial velocity at that point was about half needed for orbit.  That would indicate an impact point about 1,000 nautical miles downrange.

I wonder if the Range from Kwaj still had the ability to terminate the flight at that point.  It would have only been for engine cutoff and they would have commaneded it if the vehicle got out of it's flight path window.  E&W Ranges have the ability to destroy the second stage on other vehicles through a fairly long part of ss flight on other launchers.

[Jim]

bigdog - 21/3/2007  11:09 AM

1.  That they actually were allowed to recycle after an engine start is very impressive.  I doubt the East or West Coast Rage would allow that at the Cape or VAFB.  Having done so will give SpaceX good ammunition to convice them otherwise, will interesting to see how it develops.

2.  I wonder if the Range from Kwaj still had the ability to terminate the flight at that point.  It would have only been for engine cutoff and they would have commaneded it if the vehicle got out of it's flight path window.  E&W Ranges have the ability to destroy the second stage on other vehicles through a fairly long part of ss flight on other launchers.

1.  Not a range call.  Range has no say in mission success.

2.  It was still insight of the island so I would say yes