SpaceX Falcon 9 FT - ORBCOMM-2 - Dec. 21, 2015 (Return To Flight) DISCUSSION

[woods170]

"SpaceX launch date for return to flight now 19 Dec.- proximate cause a payload issue. AF approves booster return to land, Optimism FAA ditto"
https://twitter.com/TheLurioReport/status/673270563742289920

Lurio's tweet is deleted. Do we have any other confirmation of Dec 19?

Not surprisingly. Shortly after the tweet was published a contact of mine commented that Elon didn't approve. One doesn't go about flashing news on SpaceX when that news does not have the blessing of saint Elon himself. It's one of the very reasons why Chris only goes public with major news on SpaceX when it has been OK-ed by SpaceX. My guess is Lurio got a call from Hawthorne.

[AncientU]

Regarding the struts, the two mitigation steps I saw discussed were increasing the strength of the strut and possibly doing 100% testing. However the strut already had a more than adequate 5:1 load factor. The failure occurred because of poor control of the manufacturing process, not a design flaw.

Wrong, it is a design flaw.  Wrong, material and manufacturing technique for the application

Interesting claim.  What was the wrong material, and what was the wrong manufacturing technique?   What should they have used instead?

And why did it fly 18 times successfully if it was both wrong material and manufacturing technique?
Don't design flaws reveal themselves early?

[Jet Black]

Regarding the struts, the two mitigation steps I saw discussed were increasing the strength of the strut and possibly doing 100% testing. However the strut already had a more than adequate 5:1 load factor. The failure occurred because of poor control of the manufacturing process, not a design flaw.

Wrong, it is a design flaw.  Wrong, material and manufacturing technique for the application

Interesting claim.  What was the wrong material, and what was the wrong manufacturing technique?   What should they have used instead?

And why did it fly 18 times successfully if it was both wrong material and manufacturing technique?
Don't design flaws reveal themselves early?

Not always. Just think about various vehicle or equipment recalls. I recently had to replace my shower because of a bad design in a valve that sometimes locks up.

[Chris Bergin]

I don't know how reliable of a source this is, but:

https://twitter.com/TheLurioReport/status/673270563742289920

"SpaceX launch date for return to flight now 19 Dec.- proximate cause a payload issue. AF approves booster return to land, Optimism FAA ditto"

Fair play to him, because Orbcomm are saying the same (still a NET).

Peter B. de Selding ‏@pbdes  14m14 minutes ago
Orbcomm: Best-guess estimate of Falcon 9 Upgrade launch of our 11 sats is Dec. 19. With the usual caveats.

[abaddon]

And why did it fly 18 times successfully if it was both wrong material and manufacturing technique?
Don't design flaws reveal themselves early?

Not always. Just think about various vehicle or equipment recalls. I recently had to replace my shower because of a bad design in a valve that sometimes locks up.

So, you build your shower from scratch and throw it away every time you use it?

[cro-magnon gramps]

I don't know how reliable of a source this is, but:

https://twitter.com/TheLurioReport/status/673270563742289920

"SpaceX launch date for return to flight now 19 Dec.- proximate cause a payload issue. AF approves booster return to land, Optimism FAA ditto"

Fair play to him, because Orbcomm are saying the same (still a NET).

Peter B. de Selding ‏@pbdes  14m14 minutes ago
Orbcomm: Best-guess estimate of Falcon 9 Upgrade launch of our 11 sats is Dec. 19. With the usual caveats.

Chris, it looks to me that they are hedging their bets because the weather is unstable right now... forecast varies from day to day... we probably won't know for sure until a few days before the launch... btw, I'm just going on the basis of the public weather services... perhaps there is more detailed forecast from the "Real Weather Folks"...

[WHAP]

I don't know how reliable of a source this is, but:

https://twitter.com/TheLurioReport/status/673270563742289920

"SpaceX launch date for return to flight now 19 Dec.- proximate cause a payload issue. AF approves booster return to land, Optimism FAA ditto"

Fair play to him, because Orbcomm are saying the same (still a NET).

Peter B. de Selding ‏@pbdes  14m14 minutes ago
Orbcomm: Best-guess estimate of Falcon 9 Upgrade launch of our 11 sats is Dec. 19. With the usual caveats.

Chris, it looks to me that they are hedging their bets because the weather is unstable right now... forecast varies from day to day... we probably won't know for sure until a few days before the launch... btw, I'm just going on the basis of the public weather services... perhaps there is more detailed forecast from the "Real Weather Folks"...

I've never seen anyone move a launch day for weather more than a week in advance, except for a hurricane.  And even then it's hard to predict that far ahead.  Regardless, where did you see that the weather is unstable?  The 15 day forecast (weather.com) actually looks pretty good - all the "weather folks" get their information from the same place.  Seems to me SpaceX is still working through issues that may not be spacecraft related (no mention of any in Orbcomm's tweet).  I guess we'll see if the static fire holds for early this week, but I think they could perform it even early next week and still make the 19th.

[Chris Bergin]

I don't know how reliable of a source this is, but:

https://twitter.com/TheLurioReport/status/673270563742289920

"SpaceX launch date for return to flight now 19 Dec.- proximate cause a payload issue. AF approves booster return to land, Optimism FAA ditto"

Fair play to him, because Orbcomm are saying the same (still a NET).

Peter B. de Selding ‏@pbdes  14m14 minutes ago
Orbcomm: Best-guess estimate of Falcon 9 Upgrade launch of our 11 sats is Dec. 19. With the usual caveats.

Chris, it looks to me that they are hedging their bets because the weather is unstable right now... forecast varies from day to day... we probably won't know for sure until a few days before the launch... btw, I'm just going on the basis of the public weather services... perhaps there is more detailed forecast from the "Real Weather Folks"...

Nothing to do with forecast weather, Gramps.

[MattMason]

I don't know how reliable of a source this is, but:

https://twitter.com/TheLurioReport/status/673270563742289920

"SpaceX launch date for return to flight now 19 Dec.- proximate cause a payload issue. AF approves booster return to land, Optimism FAA ditto"

Fair play to him, because Orbcomm are saying the same (still a NET).

Peter B. de Selding ‏@pbdes  14m14 minutes ago
Orbcomm: Best-guess estimate of Falcon 9 Upgrade launch of our 11 sats is Dec. 19. With the usual caveats.

Chris, it looks to me that they are hedging their bets because the weather is unstable right now... forecast varies from day to day... we probably won't know for sure until a few days before the launch... btw, I'm just going on the basis of the public weather services... perhaps there is more detailed forecast from the "Real Weather Folks"...

From what I can understand, one advantage of a RTLS landing is simply that, if the weather is optimal for a LV to launch in Florida, the weather should be just as optimal for a stage to land close by in Florida.

To The_Other_Doug's credit from another thread, this is actually a point against RTLS in that launch weather may be based on a fully-loaded launch vehicle. A lightly-fueled first stage, with a lot of its weight gone, heading in the opposite direction, might react differently to the same winds.

[intrepidpursuit]

I don't know how reliable of a source this is, but:

https://twitter.com/TheLurioReport/status/673270563742289920

"SpaceX launch date for return to flight now 19 Dec.- proximate cause a payload issue. AF approves booster return to land, Optimism FAA ditto"

Fair play to him, because Orbcomm are saying the same (still a NET).

Peter B. de Selding ‏@pbdes  14m14 minutes ago
Orbcomm: Best-guess estimate of Falcon 9 Upgrade launch of our 11 sats is Dec. 19. With the usual caveats.

Chris, it looks to me that they are hedging their bets because the weather is unstable right now... forecast varies from day to day... we probably won't know for sure until a few days before the launch... btw, I'm just going on the basis of the public weather services... perhaps there is more detailed forecast from the "Real Weather Folks"...

From what I can understand, one advantage of a RTLS landing is simply that, if the weather is optimal for a LV to launch in Florida, the weather should be just as optimal for a stage to land close by in Florida.

To The_Other_Doug's credit from another thread, this is actually a point against RTLS in that launch weather may be based on a fully-loaded launch vehicle. A lightly-fueled first stage, with a lot of its weight gone, heading in the opposite direction, might react differently to the same winds.

It would react differently, but it also has a larger margin for error than the launching stage (no structures meters from the rocket that it might blow into, just more pad). I'd bet that all things considered the restrictions for landing are slightly less strict than the restrictions for launching.

[MarekCyzio]

From what I can understand, one advantage of a RTLS landing is simply that, if the weather is optimal for a LV to launch in Florida, the weather should be just as optimal for a stage to land close by in Florida.

I guess the most important factor is lack of vertical platform movements.

[Herb Schaltegger]

The subject of barge stability has been discussed extensively in several other threads. Summary: there is next to zero movement of the barge in ordinary sea states, horizontally or vertically. That's what all the powered stabilizers are for. A couple inches' uncertainty during a landing attempt isn't going to make or break the effort.

[Nomadd]

 The thrusters aren't stabilizers. They're station keepers. They have no effect on vertical movement.

[Johnnyhinbos]

The thrusters aren't stabilizers. They're station keepers. They have no effect on vertical movement.

True, but the size of the barge negates average sea state - i.e., if the trough to trough wavelength is shorter then the length (or width) of the barge then the movement is mainly cancelled out. At 300' x 170' this negates a lot of swell.

[Kabloona]

The barge also carries water ballast for stability.

[Roy_H]

The subject of barge stability has been discussed extensively in several other threads. Summary: there is next to zero movement of the barge in ordinary sea states, horizontally or vertically. That's what all the powered stabilizers are for. A couple inches' uncertainty during a landing attempt isn't going to make or break the effort.

It would appear that wind is the main problem to overcome landing on the ASDS. Rocket comes down leaning into the wind and then has to go vertical in very short time. The wind is still pushing on the rocket and the rotational momentum of changing to vertical is working against you. I always though it would be better to drive the ASDS in the direction of the wind to match as close as possible and land on a moving target.

[rpapo]

It would appear that wind is the main problem to overcome landing on the ASDS. Rocket comes down leaning into the wind and then has to go vertical in very short time. The wind is still pushing on the rocket and the rotational momentum of changing to vertical is working against you. I always though it would be better to drive the ASDS in the direction of the wind to match as close as possible and land on a moving target.

It's not quite an apples to apples comparison, since the speed and height were considerably less, but they did do one Grasshopper flight with a stiff cross wind.

[mme]

The subject of barge stability has been discussed extensively in several other threads. Summary: there is next to zero movement of the barge in ordinary sea states, horizontally or vertically. That's what all the powered stabilizers are for. A couple inches' uncertainty during a landing attempt isn't going to make or break the effort.

It would appear that wind is the main problem to overcome landing on the ASDS. Rocket comes down leaning into the wind and then has to go vertical in very short time. The wind is still pushing on the rocket and the rotational momentum of changing to vertical is working against you. I always though it would be better to drive the ASDS in the direction of the wind to match as close as possible and land on a moving target.

I don't think there is any evidence that wind is the main problem to overcome.  The last attempt failed because of a feedback induced control oscillation do to a sticky valve.  The previous attempt failed because the stage had to make an extreme divert with the engine because the grid fins lost control authority.

Maybe you're right, but I'd want to see hard evidence before adding the extra complexity over simply targeting fixed coordinates.

[Jim_LAX]

Think of the landing stage as a large mass consisting of 9 engines and the thrust structure, toped by a hollow aluminum sail.  As the wind hits this it will tend to rotate around its center mass rather than translate sideways.  Correcting this rotation is difficult because the grid fins are useless as the stage aproaches zero velocity at touchdown, leaving only the cold gas thrusters at the top of the rocket if you want to land in a fairly upright position, and you do.

[Coastal Ron]

It would appear that wind is the main problem to overcome landing on the ASDS.

Wind has never been mentioned as a factor in the two attempted barge landings.