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

[joek]

Landing this stage is an epic battle of precision. A battle they have not yet won.

Well, they haven't won it at sea yet.  But they have demonstrated it on land numerous times with test vehicles.

I see a lot of analogies for what they are doing as when a pilot lands an aircraft.  Ideally when landing an airplane you want to have a stabilized flight path when landing, where only small corrections need to be made.  If you have a big landing area you're shooting for (i.e. a Cessna 172 landing on a runway built for large jets) you don't have critical corrections you have to make.  But if you're an F-18 pilot coming in on an aircraft carrier at night in stormy weather, then if you need to nail that first landing you are making continuous fine & large adjustments all the way down.

To me landing on the barge is like landing on the aircraft carrier, and landing on land is like landing at the large commercial airport.

I don't have too much concern about the land landing, assuming they have the fuel to get back.

I will take that analogy further -- this is more like the difference between trying to land a new carrier jet on the carrier deck, and landing it for the first time in initial trials on the dry lake bed at Edwards AFB.  You have tens of meters of dispersion absorption capability with the RTLS without endangering anything (or anyone) and thus have an enhanced capability of getting the thing onto the ground in one piece.

(And yes, I understand that a carrier jet is Navy and wouldn't necessarily have its initial trials at Edwards -- but you know what I mean, I'm just trying to make a point.  Forgive the logical inconsistency, please.  )

These analogies and their relevance fail on several levels.  There is no pilot on board the F9.  There is no $B aircraft carrier and personnel.  The precision needed for an in-tact F9 landing at site X1 is arguably not significantly greater than a barge (~ 70Kft² vs 51Kft² with +-65ft greater latitude in one dimension, see here).  Edwards and similar test areas cover a lot of desolate area free of build-up or occupation--much more than CCAFS. Etc, etc...

Yes, SpaceX has demonstrated presision targeting of a landing location--but that is only part of the problem.  Hoverslam has not been demonstrated successfully (on land or at sea); the last barge landing was hard and resulted in a buckled leg and subsequent LOV.

Were previous barge landings unsuccessful due to movement of the barge?  Maybe, but I have not seen anything to suggest such.  Nor would the FAA or Range care; they will make their decisions based on risk to the public [1], not on "getting the thing onto the ground in one piece".

In short, the suggestion or implication that a landing at X1 is safer is wrong.  That it might be more successful than a barge landing is irrelevant.


[1]  Whicn includes not only risk to the general public, but CCAFS personnel.

[Robotbeat]

There's no such thing as 100% reliability in anything. There isn't. Nope, not even there. Always a chance of failure. Continue.

[edkyle99]

One issue of interest to me is fire-fighting preparedness for a landing attempt.  Launch pads have water deluge to reduce the risk.  I wonder about the landing pad, and about the surrounding vegetation that might be scorched by a stage running "sideways" during its final adjustments.  Imagine a stage landing safely, only to be destroyed in the subsequent grass fire!

 - Ed Kyle

[Johnnyhinbos]

I thought the deluge system on a launch pad is to reduce acoustical stress on the launch vehicle?

[edkyle99]

I thought the deluge system on a launch pad is to reduce acoustical stress on the launch vehicle?

Primarily, but it can also serve to protect the pad.  It was used when a fire broke out on the pad after an STS abort, for example.

 - Ed Kyle

[DaveS]

I thought the deluge system on a launch pad is to reduce acoustical stress on the launch vehicle?

Primarily, but it can also serve to protect the pad.  It was used when a fire broke out on the pad after an STS abort, for example.

 - Ed Kyle

Wrong system. The Sound Suppression Water System is completely separate from the FireX system as well the Base Heatshield deluge system used for RSLS aborts. The BHS was used to disperse the free GH2 exhausted by the engines during shutdown. The fire you're talking about happened on the first launch attempt of STS-41D and it was minor. All it did was erode the top coating of some of the tiles on the bodyflap. The umbilicals on the ET and the TSMs were not even scorched.

[Zed_Noir]

One issue of interest to me is fire-fighting preparedness for a landing attempt.  Launch pads have water deluge to reduce the risk.  I wonder about the landing pad, and about the surrounding vegetation that might be scorched by a stage running "sideways" during its final adjustments.  Imagine a stage landing safely, only to be destroyed in the subsequent grass fire!

 - Ed Kyle

Maybe a few well placed remote operated water cannons.

[Coastal Ron]

These analogies and their relevance fail on several levels.  There is no pilot on board the F9.

As far as we know, the stage is controlling itself, which means there is a "pilot" onboard.

The precision needed for an in-tact F9 landing at site X1 is arguably not significantly greater than a barge (~ 70Kft² vs 51Kft² with +-65ft greater latitude in one dimension, see here).

Nice graphic you put together.  But you are only considering the red circle, which has what we think is a concrete landing pad, but the much larger surrounding area (the yellow circle) would likely be able to support a landing too - although it may kick up a lot of debris that could damage the stage, but that's a reuse issue, not a landing issue.

Yes, SpaceX has demonstrated presision targeting of a landing location--but that is only part of the problem.  Hoverslam has not been demonstrated successfully (on land or at sea); the last barge landing was hard and resulted in a buckled leg and subsequent LOV.

Were previous barge landings unsuccessful due to movement of the barge?  Maybe, but I have not seen anything to suggest such.

You appear to be making judgements based on incomplete data, since you don't seem to know what has happened with the two previous barge landing attempts.

- SpaceX CRS-5 was the 1st barge landing attempt, and the first to use the grid fins.  Unfortunately the grid fin system ran out of hydraulic fluid, which led to alignment issues, and resulted in the stage impacting the barge with a horizontal velocity.

- SpaceX CRS-6 was the 2nd barge landing attempt.  The grid fins had enough hydraulic fluid this time, but a stuck valve on the center engine meant that the stage was too slow in responding to errors, and it too built up too much horizontal velocity as it attempted to correct when it reached the barge.

So we have not seen a barge landing attempt where their systems are all functioning nominally.

In short, the suggestion or implication that a landing at X1 is safer is wrong.  That it might be more successful than a barge landing is irrelevant.

Rockets blowing up at the Cape is nothing new, so I'm sure the FAA and Air Force are looking at whether the landing attempt would be safe for humans.  Which will be a different standard than if the decision was based on scratching the paint at the landing site - someone has to do it sooner or later, so...

[LouScheffer]

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?

[Jim]

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

Not a claim. See upthread. 

[joek]

...

The assertion was that landing at X1 would be as safe or safer than a barge landing.  That is demonstrably false.  The rest of my post was intended to illustrate the fallacy of that assertion.  You have presented no arguments which refute that fallacy.

If you want to argue that landing at X1 has a higher probability of a success than on a barge, fine--no argument.  If you want to argue that landing at X1 is as safe or safer than a barge landing, nothing have been presented to support that opinion.

I have no problem with a landing at X1.  Nor do I belive that a successful barge landing is required prior to an X1 landing.  What I have a problem with is hand-waving and assertions based on bad analogies and incomplete facts leading to erroneous conclusions.

[Coastal Ron]

The assertion was that landing at X1 would be as safe or safer than a barge landing.  That is demonstrably false.  The rest of my post was intended to illustrate the fallacy of that assertion.  You have presented no arguments which refute that fallacy.

You stated that the Falcon 9 1st stage has no pilot as part of your proof.  And I pointed out that it does have a pilot, just not human.  And you did not show how having or not having a human pilot makes piloting the 1st stage LESS safe.

If you want to argue that landing at X1 has a higher probability of a success than on a barge, fine--no argument.  If you want to argue that landing at X1 is as safe or safer than a barge landing, nothing have been presented to support that opinion.

I don't understand your logic.  Are you saying that being able to make a successful landing has no correlation to safety?  That makes no sense.

As to what I presented, it could be argued that given a larger potential landing area than the barge, that both the SpaceX CRS-5 & -6 stages would have had a higher potential for a successful landing since they wouldn't have had to correct their horizontal location on descent.  So the larger landing area at X1, even outside of the paved landing area, increases their chances for landing successfully.

And until you explain how the chance for success has no bearing on safety, I think I've presented enough information.

What I have a problem with is hand-waving and assertions based on bad analogies and incomplete facts leading to erroneous conclusions.

I agree that analogies are not perfect, but they can illustrative.  For instance, though I never landed an F-18 on an aircraft carrier, I have landed Cessna's at large and small airports, so maybe you have to be a pilot to truly appreciate the analogy.

As to "incomplete facts", remember you were unaware of the facts regarding the two failed landings, which is why I recounted them.  So imagine my frustration with your assertions when it was clear they were being made with "incomplete facts leading to erroneous conclusions."

I'm done with this conversation, so you can have the last word.

[mme]

...
I ran out of attention, but plan to add more pads and assets.

http://tiny.cc/ksc-ccafs-assets-map
...

Nice map, but if you are going to mark LC-39, which is way up north, you should mark the CCAFS buildings, which are much closer to the west.
There is one remote building with parked cars WSW of X1.  How far is that?

Well, LC-39 was there because I started geeking out and trying to map everything that caught my attention in KSC / CCAFS.  I've continued adding landmarks to it and making it more of a general reference for me.  Here is a new map specifically measuring distances to property around X1:

http://tiny.cc/property-near-x1-map

Google Maps is a crude GIS tool, but I drew lines to all surrounding property I could find and labelled them with the distance from X1.  Labels show at the midpoints and may require zooming in.  The only things I could find under a mile away were the Mercury 7 Monument and Blockhouse at LC-14.

Obviously I could have missed something, but I thought it might be interesting to have some rough idea of what's near X1.

[LouScheffer]

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

Not a claim. See upthread. 

I have reviewed the thread, and still see no evidence for these claims.  What I've seen is that the failed material was steel, and SpaceX was thinking of changing to Inconel.  However, this was explicitly stated to be preliminary, so they had not yet concluded steel was the wrong material.  And I've seen no evidence that steel was a wrong choice (in fact there have been many comments that stainless steel, at least, has excellent properties at cryogenic temperature).

Likewise, the problem was stated to be bad grain structure in the bolt head.  It was not stated, to my knowledge, whether the technique (such as heat treating, or some machining step) was bad, or it was correct technique, just poorly executed.

Your claim is quite a bit stronger:

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

So is there more evidence for "wrong material"?  And what is the evidence for "wrong technique", as opposed to perfectly good technique, poorly executed?

[edkyle99]

The fire you're talking about happened on the first launch attempt of STS-41D and it was minor.

I was in a control room at KSC, watching the fire on a closed circuit monitor as it was happening.  It sure looked serious to me, a fire at the base of a live, fueled launch vehicle with people sitting on top.  I was very happy to see the water turned on.  That was my point, about the water.  I'm wondering if X1 has a water spraying system.

 - Ed Kyle

[woods170]

The fire you're talking about happened on the first launch attempt of STS-41D and it was minor.

I was in a control room at KSC, watching the fire on a closed circuit monitor as it was happening.  It sure looked serious to me, a fire at the base of a live, fueled launch vehicle with people sitting on top.  I was very happy to see the water turned on.  That was my point, about the water.  I'm wondering if X1 has a water spraying system.

 - Ed Kyle

No analogy with STS here. There will be no people sitting on top of any first stage that lands at X1.

[saliva_sweet]

Imagine a stage landing safely, only to be destroyed in the subsequent grass fire!

The only thing more ironic would be to have a good recovery ruined by landing on top of a water cannon designed to save the stage from grass fires.

[Raul]

"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?

[Blizzzard]

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

Well that's potentially quite interesting - I'd not heard from another source about this so maybe it was either false information or one of the parts could be inaccurate. It could be that launch may still be pushed back, but the landing comments or FAA could have rejected landing attempt..

Anyway, I'm still hoping for a 16th launch, with RTLS - must stay optimistic!

[MarekCyzio]

Rockets blowing up at the Cape is nothing new, so I'm sure the FAA and Air Force are looking at whether the landing attempt would be safe for humans.  Which will be a different standard than if the decision was based on scratching the paint at the landing site - someone has to do it sooner or later, so...

Landing is very different from launches. Range Safety has ample time to make decision during launches. With SpaceX landing delaying destruct command a couple of seconds may result in debris field hitting multi billion $ buildings in CCAFS (EPF) or even worse the fuel farm in Port Canaveral. Falcon 9 trajectory before the last burn is going directly towards these areas. I have full confidence in range safety but landings will be completely new challenge for them - something they didn't have to deal with since Snark times.