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

[cordor]

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?

My guess is, after stage2 wait and clear ISS, mostly it will miss the satellite slot registered to og2.  It may have to wait couple days for second chance of orbital insertion, by then there won't be enough LOX and RP-1 will be frozen to rock solid.

[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?

My guess is, after stage2 wait and clear ISS, mostly it will miss the satellite slot registered to og2.  It may have to wait couple days for second chance of orbital insertion, by then there won't be enough LOX and RP-1 freeze to rock solid..

True, but Joffan's suggestion was that precisely because of that, if proper orbital insertion is canceled, they'd circularize instead, which is A) a safe maneuver that will do no harm, so has less (no) gates it has to pass, and B) a pre-calculated maneuver that can be approved in advance, so does not require real-time risk-assessment.

[cordor]

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?

My guess is, after stage2 wait and clear ISS, mostly it will miss the satellite slot registered to og2.  It may have to wait couple days for second chance of orbital insertion, by then there won't be enough LOX and RP-1 freeze to rock solid..

True, but Joffan's suggestion was that precisely because of that, if proper orbital insertion is canceled, they'd circularize instead, which is A) a safe maneuver that will do no harm, so has less (no) gates it has to pass, and B) a pre-calculated maneuver that can be approved in advance, so does not require real-time risk-assessment.

And if spacex miss the first launch window on the ground, have to launch few days later, you have another backup too?

[Dappa]

True, but Joffan's suggestion was that precisely because of that, if proper orbital insertion is canceled, they'd circularize instead, which is A) a safe maneuver that will do no harm, so has less (no) gates it has to pass, and B) a pre-calculated maneuver that can be approved in advance, so does not require real-time risk-assessment.

And hope that this contingency circularized orbit doesn't interfere with Dragon ops.

[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?

My guess is, after stage2 wait and clear ISS, mostly it will miss the satellite slot registered to og2.  It may have to wait couple days for second chance of orbital insertion, by then there won't be enough LOX and RP-1 freeze to rock solid..

True, but Joffan's suggestion was that precisely because of that, if proper orbital insertion is canceled, they'd circularize instead, which is A) a safe maneuver that will do no harm, so has less (no) gates it has to pass, and B) a pre-calculated maneuver that can be approved in advance, so does not require real-time risk-assessment.

And if spacex miss the first launch window on the ground, have to launch few days later, you have another backup too?

A circle is a circle is a circle.   If we already know we're at a certain post-launch orbit with a safe (below ISS) Apogee, I don't see the harm in circularizing it as a plan B.

Your argument about a delayed launch actually applies to the plan A maneuver (which will have to be re-approved for every delay), but not to the plan B.

[Antares]

Its fate was sealed months ago by the deal between NASA and SpaceX.

Are you suggesting the health checks were overly conservative?  It sounds like you know something about the monte-carlo simulations that were done.  From how I understood Chris's article, I was thinking the fate was sealed by an underperforming launch vehicle that did not have enough propellant remaining to do the second burn.

[Rocket Science]

NASA TV Coverage of Dragon at ISS begins 4am Eastern time Wednesday October 10th with grapple at 7:32 am.

[Mike_1179]

Its fate was sealed months ago by the deal between NASA and SpaceX.

Are you suggesting the health checks were overly conservative?  It sounds like you know something about the monte-carlo simulations that were done.  From how I understood Chris's article, I was thinking the fate was sealed by an underperforming launch vehicle that did not have enough propellant remaining to do the second burn.

Second burn plus disposal burn.  Would the LV have to calculate if it had sufficient propellant to both circularize the secondary payload then remove itself?  You can see there are many different permutations for various levels of 1st and 2nd stage performance - what if there was a general degradation in performance like the Delta IV earlier this week, would the LV have to take that into account?  Like Jim said, LV don't make this type of decision.

[LegendCJS]

Its fate was sealed months ago by the deal between NASA and SpaceX.

Are you suggesting the health checks were overly conservative?  It sounds like you know something about the monte-carlo simulations that were done.  From how I understood Chris's article, I was thinking the fate was sealed by an underperforming launch vehicle that did not have enough propellant remaining to do the second burn.

I don't know anything other than what I read on this site (I don't even have L2).  I think its just semantics.  The outcome of low second stage fuel the pre-determined from SpaceX's pre launch agreement with NASA. So was the "fate sealed" when the agreement was made or was the "fate sealed" when low fuel occurred?

Since my post was in response to people asking why didn't SpaceX make a second burn attempt to at least circularize the orbit, I focused on the old agreement as the deciding event.

[cordor]

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?

My guess is, after stage2 wait and clear ISS, mostly it will miss the satellite slot registered to og2.  It may have to wait couple days for second chance of orbital insertion, by then there won't be enough LOX and RP-1 freeze to rock solid..

True, but Joffan's suggestion was that precisely because of that, if proper orbital insertion is canceled, they'd circularize instead, which is A) a safe maneuver that will do no harm, so has less (no) gates it has to pass, and B) a pre-calculated maneuver that can be approved in advance, so does not require real-time risk-assessment.

And if spacex miss the first launch window on the ground, have to launch few days later, you have another backup too?

A circle is a circle is a circle.   If we already know we're at a certain post-launch orbit with a safe (below ISS) Apogee, I don't see the harm in circularizing it as a plan B.

Your argument about a delayed launch actually applies to the plan A maneuver (which will have to be re-approved for every delay), but not to the plan B.

what circle I thought stage2 was locked within iss zone. no burning.

[cleonard]

One thing kind of bothers me about the whole "not enough fuel" to preform the burn to boost the Orbcomm payload.  The amount of fuel is really not that much.  I don't know the dry mass of the second stage so I can't really do the calculations, but the burn time has got to be only a few seconds.  I've not run the exact numbers but to get from the initial orbit to the planned Orbcomm release orbit is something like 225m/s at most. 

I don't remember the weights but a low on fuel second stage without the Dragon has got to have at least 4 g acceleration.   It's 5 seconds of that to get the needed 225m/s and another 5 seconds or so to dispose of the stage.

What this tells me is that the Dragon just barely made it to the intended orbit with essentially zero fuel margin.  The other possibility is that any chance for a second burn was tossed out the moment the first stage engine quit due to the programming of the flight computer. 

[meekGee]

A circle is a circle is a circle.   If we already know we're at a certain post-launch orbit with a safe (below ISS) Apogee, I don't see the harm in circularizing it as a plan B.

what circle I thought stage2 was locked within iss zone. no burning.

That's not my understanding.

I think second stage finishes its first burn at something like a 300x200 km orbit. Dragon is released, and then heads towards the ISS, approaching carefully from below.

The second burn of the the second stage is a ISS orbit crossing burn, and it has to be pre-approved by humans.  So unless the starting parameters are exactly as prescribed, the default action is no-go, which is understandable.

Jotten proposed a different default, fail-safe, action:  circularize to 300x300, since then the life of the secondary will be extended.

Jim said "LVs don't do that", and I asked why, that's all.

I can't see why this plan-B course of action can't be approved and pre-programmed in advance, irrespective of why plan-A didn't execute.

I'm saying this after seeing that both the first stage (Falcon) and the second stage (Delta) used a lot of discretion in adapting to situations which were much less certain.  If they were to give up and play dead at the first sign of trouble, those would have been better times to quit.

[titanmiller]

What this tells me is that the Dragon just barely made it to the intended orbit with essentially zero fuel margin. 

Is it possible that the F9 is drastically under performing compared to its specifications?

[cordor]

A circle is a circle is a circle.   If we already know we're at a certain post-launch orbit with a safe (below ISS) Apogee, I don't see the harm in circularizing it as a plan B.

what circle I thought stage2 was locked within iss zone. no burning.

That's not my understanding.

I think second stage finishes its first burn at something like a 300x200 km orbit. Dragon is released, and then heads towards the ISS, approaching carefully from below.

The second burn of the the second stage is a ISS orbit crossing burn, and it has to be pre-approved by humans.  So unless the starting parameters are exactly as prescribed, the default action is no-go, which is understandable.

Jotten proposed a different default, fail-safe, action:  circularize to 300x300, since then the life of the secondary will be extended.

Jim said "LVs don't do that", and I asked why, that's all.

I can't see why this plan-B course of action can't be approved and pre-programmed in advance, irrespective of why plan-A didn't execute.

I'm saying this after seeing that both the first stage (Falcon) and the second stage (Delta) used a lot of discretion in adapting to situations which were much less certain.  If they were to give up and play dead at the first sign of trouble, those would have been better times to quit.

iss can go as low as 330km, right now orbcomm apogee is at 320km, you make a circle there, it's kinda pretty close.

[joek]

One thing kind of bothers me about the whole "not enough fuel" to preform the burn to boost the Orbcomm payload.  The amount of fuel is really not that much.  I don't know the dry mass of the second stage so I can't really do the calculations, but the burn time has got to be only a few seconds.  I've not run the exact numbers but to get from the initial orbit to the planned Orbcomm release orbit is something like 225m/s at most. 

I don't remember the weights but a low on fuel second stage without the Dragon has got to have at least 4 g acceleration.   It's 5 seconds of that to get the needed 225m/s and another 5 seconds or so to dispose of the stage.

What this tells me is that the Dragon just barely made it to the intended orbit with essentially zero fuel margin.  The other possibility is that any chance for a second burn was tossed out the moment the first stage engine quit due to the programming of the flight computer. 

May also be due to other factors; posibly power.  You have a couple sats sitting there which must either be drawing power from F9-S2, which has limited capability, or (as suggested upthread), must be let loose to draw their own power.

No idea how long the F9-S2 could provide power to the OG2's (or if that was possible), or how long the OG2's could sit on F9-S2 without power before they needed to be released, but likely a constraint.  No idea if it was significant.

[upjin]

A circle is a circle is a circle.   If we already know we're at a certain post-launch orbit with a safe (below ISS) Apogee, I don't see the harm in circularizing it as a plan B.

what circle I thought stage2 was locked within iss zone. no burning.

That's not my understanding.

I think second stage finishes its first burn at something like a 300x200 km orbit. Dragon is released, and then heads towards the ISS, approaching carefully from below.

The second burn of the the second stage is a ISS orbit crossing burn, and it has to be pre-approved by humans.  So unless the starting parameters are exactly as prescribed, the default action is no-go, which is understandable.

Jotten proposed a different default, fail-safe, action:  circularize to 300x300, since then the life of the secondary will be extended.

Jim said "LVs don't do that", and I asked why, that's all.

I can't see why this plan-B course of action can't be approved and pre-programmed in advance, irrespective of why plan-A didn't execute.

I'm saying this after seeing that both the first stage (Falcon) and the second stage (Delta) used a lot of discretion in adapting to situations which were much less certain.  If they were to give up and play dead at the first sign of trouble, those would have been better times to quit.

You bring up a valid point from the perspective that if you have engine-out capability, plans should be in place for both the primary and secondary missions.  The value of engine-out capability is in completing the missions or saving lives, not simply in having it.

It will be interesting if the present situation results in any new plans by SpaceX in respect to accomplishing the secondary mission if an engine fails.  I would think, particularly with non-NASA customers, that additional contingency plans would be created to increase the chances of completing the secondary mission whenever possible.  In the case of when NASA is their primary customer, things would likely be handled differently.

[pericynthion]

What this tells me is that the Dragon just barely made it to the intended orbit with essentially zero fuel margin. 

Is it possible that the F9 is drastically under performing compared to its specifications?

Perhaps not "drastically", but that would fit with the light cargo loading of Dragon on C2+ and CRS-1, the instantaneous launch windows, and the plan to move to Falcon 1.1 for CRS-3 onwards.

[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.

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?

It doesn't have the data or capability to make the decisions or to follow a different trajectory.

No, the Delta did not react to anomaly.  It didn't do anything different.  It shutdown the engine when it reached a certain velocity.

[Jim]

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.

Yes it is.  It doesn't have enough data to such a decision nor is possible to design a contingency orbit that covers all the possibilities.

[Jim]

True, but Joffan's suggestion was that precisely because of that, if proper orbital insertion is canceled, they'd circularize instead, which is A) a safe maneuver that will do no harm, so has less (no) gates it has to pass, and B) a pre-calculated maneuver that can be approved in advance, so does not require real-time risk-assessment.

No, because there are too many initial conditions to cover and to determine A and therefore impossible to compute B