SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION

[Jason Davies]

All this discussion of the Falcon 9, especially when we don't have the full facts yet, and everyone seems to have forgotten about the Dragon which was less we forget the whole point of this flight.

You will always get that on a massive site like this. It's still superior to any other site even half this site's size.

Plus I mainly use L2, which is very pure high level NASA etc people, so I'm happy But even Chris wrote an article to try and tame a few people.

http://www.nasaspaceflight.com/2012/10/dragon-iss-spacex-review-falcon-9-ascent-issues/

"Successful" is the accurate way to portray the launch, given Falcon 9's primary objective was to loft Dragon uphill to his orbital destination.

[ugordan]

Perhaps if SpaceX did a little better job programming their upper stage avionics, it could have been able to restart.

What do you mean by this?

I mean, perhaps the upper stage might have been able to recalculate a new trajectory for restart that would've satisfied the ISS safety gate. I don't know if that was even physically possible at that point, and getting the ISS safety folks to believe that the upper stage could calculate it safely and autonomously would've been a tall order.

I don't know all the sorts of things the safety gate entailed, but my impression is that the primary consideration was propellant quantity and only the perigee and apogee of the target orbit, not other parameters like argument of perigee etc.

In other words, if let's say an underburn orbit of 400x330 km would be undesirable based on default SES-2 TIG, *any* orbit with those parameters would be bad, regardless of Orbcomm phasing w/respect to ISS. If they ran Monte Carlo simulations, they watched the evolutions of orbits with different perigee/apogee with respect to ISS and probably excluded the whole range or perigee/apogee combinations, regardless of phasing angle as orbital evolution would rapidly change that anyway.

If that is the case, then there really was nothing the upper stage could have "recalculated" that would have changed the safety criteria outcome - high enough apogee.

[Robotbeat]

Perhaps if SpaceX did a little better job programming their upper stage avionics, it could have been able to restart.

What do you mean by this?

I mean, perhaps the upper stage might have been able to recalculate a new trajectory for restart that would've satisfied the ISS safety gate. I don't know if that was even physically possible at that point, and getting the ISS safety folks to believe that the upper stage could calculate it safely and autonomously would've been a tall order.

I don't know all the sorts of things the safety gate entailed, but my impression is that the primary consideration was propellant quantity and only the perigee and apogee of the target orbit, not other parameters like argument of perigee etc.

In other words, if let's say an underburn orbit of 400x330 km would be undesirable based on default SES-2 TIG, *any* orbit with those parameters would be bad, regardless of Orbcomm phasing w/respect to ISS. If they ran Monte Carlo simulations, they watched the evolutions of orbits with different perigee/apogee with respect to ISS and probably excluded the whole range or perigee/apogee combinations, regardless of phasing angle as orbital evolution would rapidly change that anyway.

If that is the case, then there really was nothing the upper stage could have "recalculated" that would have changed the safety criteria outcome - high enough apogee.

Yes, that's what I meant by "don't know if that was even physically possible at that point." Thanks for explaining it a little better. But it's also possible they didn't run the trajectory they actually ended up at, or weren't able to get prior permission for such a trajectory but may have been able to get permission after the engine failure.

Just speculation, I guess.

[sdsds]

It isn't clear an insurance company will pay out to Orbcomm. SpaceX could have partially "insured" them in the contract with a zero-cost reflight of a single OG2 if something went amiss on this launch.

What secondary payloads have been planned for SpX-2?

[Robotbeat]

It isn't clear an insurance company will pay out to Orbcomm. SpaceX could have partially "insured" them in the contract with a zero-cost reflight of a single OG2 if something went amiss on this launch.

What secondary payloads have been planned for SpX-2?

Perhaps a partial insurance payment?

[iamlucky13]

Perhaps if SpaceX did a little better job programming their upper stage avionics, it could have been able to restart.

What do you mean by this?

I mean, perhaps the upper stage might have been able to recalculate a new trajectory for restart that would've satisfied the ISS safety gate. I don't know if that was even physically possible at that point, and getting the ISS safety folks to believe that the upper stage could calculate it safely and autonomously would've been a tall order.

I wonder if perhaps they left it with a much simpler logic for this flight. IE - if the fuel quantity is within the nominally specified range, ok to proceed. Otherwise, cancel.

In such case, they may have actually had plenty of fuel to proceed, but not have satisfied the primary customer's requirements for risk analysis. They know the fuel quantity is off, but they can't necessarily predict all the reasons ahead of time why that would be so. As a result, they may default to presuming a fuel value that does not match the predicted value means the value is unreliable.

Just speculating...a $7 million satellite or whatever the value was justifies a somewhat limited investment in the software and risk analysis work to cover every contingency.

Of course, the engine computers are in hardened boxes at the top of the engine, so the fact that they continued to send telemetry to the flight computer doesn't mean that the rest of the engine wasn't pretty thoroughly beat-up.

There is no data for the computer to send unless the sensors are intact. Data showing a dropoff in engine performance is different than all the data channels reading flat. SpaceX engineers would have a very good idea which sensors are functioning properly in real time.

Unless and until SpaceX clarifies, we have limited info to use to guess the degree of damage the engine really took, but we do have some.

SpaceX's statement indicates at least some of the sensors were functioning, not just the computers, and they have apparent reason to believe the failure occurred in and was limited to the fuel dome, although obviously there was secondary damage such as to the fairing.

[cleonard]

... did I miss anything?

One thing that I've not seen in this thread is that the launch happened according to schedule.  I do believe this is a first for SpaceX.  I'm not sure, but I seem to remember that pretty much every previous SpaceX mission had delays. 

Now the original date for this mission did change, but I believe it was due to NASA and not SpaceX.

[Cherokee43v6]

Isn't it rather late in the history of this engine for there to be a failure of this type, if indeed it was a rupture of the fuel dome? I would have expected something like this much earlier in development.

One failure out of about 43? It could've been a manufacturing defect (or something unrelated to the engine, like something flew loose at Max-Q and hit the fuel dome), not an engine design flaw.

2 out of 44 actually... F1 flt 1 the corroded nut

[Joffan]

The obvious (in hindsight) fallback activity for the upper stage, once it failed propellent limits to clear the ISS, would have been to circularize Orbcomm at the insertion orbit apogee. Still below the ISS, still suboptimal, but much longer duration test phase. It's Orbcomm's perigee that will drive quick orbit decay here.

As ever, there may be details that prevent this. But most of the pieces would be in place for this alternative scheme I believe.

[Robotbeat]

Isn't it rather late in the history of this engine for there to be a failure of this type, if indeed it was a rupture of the fuel dome? I would have expected something like this much earlier in development.

One failure out of about 43? It could've been a manufacturing defect (or something unrelated to the engine, like something flew loose at Max-Q and hit the fuel dome), not an engine design flaw.

2 out of 44 actually... F1 flt 1 the corroded nut

No, that was a Merlin 1A, different engine.

[upjin]

In my books, that makes FOUR consecutive successful Falcon 9 launches;
asterix or no asterix.
Insurance companies like that. They're paying attention.

Wrong.  In their books, it is not.

Why not? My assumption would be that getting Dragon berthed is good, and much better than not making it to the ISS.

The secondary mission mattered.

I agree with Jim, the secondary mission matters.

However, we should be looking at the missions separately.  Failure of the secondary mission, does NOT necessarily mean failure of the entire mission, nor in this particular case.  If SpaceX completes its primary mission, they should get credit for that.

And, to call the secondary mission a complete failure, we need to define what that mission was.  We are still missing facts on the ORBCOMM's prototype mission objectives.  Lower orbit, doesn't necessarily mean mission failure, though it is a missed objective.  It might be better to define the secondary mission as a partial success or partial failure, depending on how you look at that "half a glass of water".

[Jim]

The obvious (in hindsight) fallback activity for the upper stage, once it failed propellent limits to clear the ISS, would have been to circularize Orbcomm at the insertion orbit apogee. Still below the ISS, still suboptimal, but much longer duration test phase. It's Orbcomm's perigee that will drive quick orbit decay here.

launch vehicles don't make those type decisions.

[meekGee]

The obvious (in hindsight) fallback activity for the upper stage, once it failed propellent limits to clear the ISS, would have been to circularize Orbcomm at the insertion orbit apogee. Still below the ISS, still suboptimal, but much longer duration test phase. It's Orbcomm's perigee that will drive quick orbit decay here.

launch vehicles don't make those type decisions.

Why not?  Clearly the first stage is pre-programmed to calculate trajectory and thrust levels based on real-time event.  Clearly the Delta upper stage reacted to its second stage anomaly.  Why not program a contingency trajectory in case the first-choice maneuver is canceled?

[joek]

The obvious (in hindsight) fallback activity for the upper stage, once it failed propellent limits to clear the ISS, would have been to circularize Orbcomm at the insertion orbit apogee. Still below the ISS, still suboptimal, but much longer duration test phase. It's Orbcomm's perigee that will drive quick orbit decay here.

launch vehicles don't make those type decisions.

Is there a bright line that defines what types of decisions a launch vehicle can or should make, and those it may not or should not make?

[GalacticIntruder]

I see Wikipedia has been going back and forth since the launch. Wonder why?  It is now being labeled a 'partial failure'.

I prefer to call it a 'partial success'. Primary success in orbital insertion, secondary failed.

[Robotbeat]

I see Wikipedia has been going back and forth since the launch. Wonder why?  It is now being labeled a 'partial failure'.

I prefer to call it a 'partial success'. Primary success in orbital insertion, secondary failed.

It's no more a failure than those Shuttle flights, which Wikipedia calls successes.

[LegendCJS]

The obvious (in hindsight) fallback activity for the upper stage, once it failed propellent limits to clear the ISS, would have been to circularize Orbcomm at the insertion orbit apogee. Still below the ISS, still suboptimal, but much longer duration test phase. It's Orbcomm's perigee that will drive quick orbit decay here.

launch vehicles don't make those type decisions.

Is there a bright line that defines what types of decisions a launch vehicle can or should make, and those it may not or should not make?

NASA would only allow the second stage to restart AT ALL if it was in perfect health and had all the fuel it needed for the pre-planed burn.  This is the deal NASA and SpaceX worked out to even allow SpaceX to carry a secondary payload.  It took significant time with monte-carlo simulations to work out the probabilities of damage to the ISS and decided if the pre-planed burn was safe.

In order to even consider attempting any other type of restart burn NASA and their simulation team would have to sign off on it, necessitating another significant analysis period.  By then the second stage would have re-entered.  So everyone please stop complaining about what SpaceX should have done with the second stage.  Its fate was sealed months ago by the deal between NASA and SpaceX.

[Joffan]

The obvious (in hindsight) fallback activity for the upper stage, once it failed propellent limits to clear the ISS, would have been to circularize Orbcomm at the insertion orbit apogee. Still below the ISS, still suboptimal, but much longer duration test phase. It's Orbcomm's perigee that will drive quick orbit decay here.

launch vehicles don't make those type decisions.

Is there a bright line that defines what types of decisions a launch vehicle can or should make, and those it may not or should not make?

NASA would only allow the second stage to restart AT ALL if it was in perfect health and had all the fuel it needed for the pre-planed burn.  This is the deal NASA and SpaceX worked out to even allow SpaceX to carry a secondary payload.  It took significant time with monte-carlo simulations to work out the probabilities of damage to the ISS and decided if the pre-planed burn was safe.

In order to even consider attempting any other type of restart burn NASA and their simulation team would have to sign off on it, necessitating another significant analysis period.  By then the second stage would have re-entered.

... which is why it would have to have been a pre-programmed contingency, not an on-the-fly decision. When I said "fallback activity" I intended to draw a distinction from a flight-time decision commanded from the ground.

The upper stage was testing how much propellant it had remaining, as I understand it. After the "no-go for main orbit", there's nothing computationally hard about making a second decision, "go/no-go for contingency orbit", based on that same result.

[joek]

So everyone please stop complaining about what SpaceX should have done with the second stage.  Its fate was sealed months ago by the deal between NASA and SpaceX.

I see a number of questions, but little complaining.

Is this the type of decision-making that is Just Not Done due to LV avionics (or whatever) limitations?  Convention or historical reasons?  A "deal" that required a picture-perfect flight for nominal Orbcomm insertion?  Exhaustion of pre-flight analysis resources?  Or that most every contingency was pre-analyzed and pre-programmed and there simply were no better options due to propellant, power, position, whatever?

Obviously details won't be known for some time (if ever), but it would be interesting to understand the typical constraints, especially with regards to modern avionics and associated decision-making.

[Joffan]

The obvious (in hindsight) fallback activity for the upper stage, once it failed propellent limits to clear the ISS, would have been to circularize Orbcomm at the insertion orbit apogee. Still below the ISS, still suboptimal, but much longer duration test phase. It's Orbcomm's perigee that will drive quick orbit decay here.

launch vehicles don't make those type decisions.

Since we are discussing a launch vehicle that made precisely that type of decision - whether or not to burn for a particular orbit - I think you must have misunderstood my suggestion. This is a very simple decision tree I'm talking about here. The launch vehicle is doing no more decision-making than comparing the remaining propellant mass to a threshold, which it has already done once to make the no-go decision for the target orbit. Meet the lower threshold = execute the burn for the contingency orbit.