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

[johnnyhinbos01]

Excuse me if I misunderstand this, but hasn't some journalist or other said that Spacex hopes the next landing to be on land before a great deal of landing attempts? What makes this different?

SFAIK the constraint preventing landing on land has not been the rocket crashing into the pad and blowing up; that would not damage any government or public property. The reason the offshore landings were required was to demonstrate that the booster could return from the actual launch trajectory to the landing pad accurately, remain under control, and not go off course and damage government or private property or endanger human lives. AIUI the return trajectory used with the barge was the same as the one that will be used for recovery on land, the return burn was just delayed a few seconds to move the landing point offshore.

SpaceX has already demonstrated the capability to land a booster stage intact on the ground quite a few times, although obviously several design problems have been identified during the barge landing attempts and the design has evolved.

How off from the launch trajectory is the return trajectory? Meaning, if range control is ok with the launch then wouldn't it be okay  for the RTL? I assume the same ordnance is still in place if things go pear shaped. And a booster (and second stage) loaded with fuel is probably a bigger concern than a nearly empty booster with no second stage.

[edkyle99]

might be good to get some pics of the LC-1 site and while we are in the area Blue's site LC-36 might be fun to watch

Cape Canaveral LC 1 is a Snark launch complex that was retired in 1960. 

The landings are to be at the former LC 13, which SpaceX is calling "Landing Complex 1" to confuse historians.  I would prefer they named it "Landing Pad 1" or "Landing Site 1" or some such to provide historical clarity, but no one listens to me. 
http://www.globalsecurity.org/jhtml/jframe.html#http://www.globalsecurity.org/space/library/report/1991/6555th/12snklcz.jpg|||[Photo]

 - Ed Kyle

[Coastal Ron]

SpaceX hopes to land next F9 booster on land at "Landing Complex-1" at Cape Canaveral Air Force Station.

We know that ORBCOMM-2 is a light payload that is only headed to LEO, so maybe that will allow SpaceX to maximize their fuel load so the stage can make it back to the launch site?

[GalacticIntruder]

Does seem very risky to me since they have never landed successfully on the barge-Drone Ship. But maybe terra firma is actually easier. 

I hope it is not because of Blue. Musk's competition with Bezos could backfire. Either SpX goes for the TKO or Musk has to eat humble pie and get tarred by the MSM.

[Kabloona]

Does seem very risky to me since they have never landed successfully on the barge-Drone Ship. But maybe terra firma is actually easier. 

I hope it is not because of Blue. Musk's competition with Bezos could backfire. Either SpX goes for the TKO or Musk has to eat humble pie and get tarred by the MSM.

What's the risk? That the booster crashes? It's already crash landed in the ocean and on the barge. Worst case now is it crashes on an empty expanse of concrete. Why is that any worse?

As for being "tarred" by the MSM, all previous "failed" landing attempts will be forgotten about 5 minutes after the first successful SpaceX landing and Musk will be toasted as the second coming of Werner von Braun, albeit without the unfortunate political baggage.

So I doubt Musk is worried. He's playing the long game, and one or two more failed landing attempts aren't going to prevent an ultimately successful landing.

Which will then immediately eclipse Blue's media coup, since a potentially reusable orbital booster stage is a much bigger deal than a potentially reusable tourist ride.

[mme]

...
How off from the launch trajectory is the return trajectory? Meaning, if range control is ok with the launch then wouldn't it be okay  for the RTL? I assume the same ordnance is still in place if things go pear shaped. And a booster (and second stage) loaded with fuel is probably a bigger concern than a nearly empty booster with no second stage.

I think it's the difference between being Willian Tell and the child with the apple on his head.

I don't think the similarity of the trajectories matters, but for what it's worth LC-13 is about 5.5 miles south of LC-40.  What matters is ensuring that the impact point of the stage at any point in the return can't cause damage or injury.  I think the actual risk is low, but it's reasonable for people to be nervous and careful.  Going "pear shaped" is not slamming into the pad, it's a high trajectory with a failed FTS kills someone.

Not likely, but you don't don't want to be the person that rubber stamped it without double checking every contingency.

[mme]

...
my guess is that some pretty heavy arm twisting is in process to go from a barge landing to land and doing so in a brand new launcher that has never flown.

puts more popcorn on the list

I don't understand what leverage SpaceX could possibly have to twist anyone's arm.  I think that that AF and NASA are interested in advancing the state of the art.  At the same time I think it's reasonable for them to be cautious.  At least 2 barge attempts have been "close enough for horse shoes."  It's pretty desolate around LC-13, it's reasonable to give them a shot if they are confident that the FTS will allow them to fall short should the need arise.

The closest non-pad related structure I could find on Google maps is a mile away.  The collection of buildings to the west is 1.8 miles away.  There may be important/expensive assets closer, but nothing obvious.

Edit: Fixed quote, added distance reference.

[abaddon]

I don't understand what leverage SpaceX could possibly have to twist anyone's arm.

They don't have any; you need to consider the source of the comment.

[LastStarFighter]

Does seem very risky to me since they have never landed successfully on the barge-Drone Ship. But maybe terra firma is actually easier. 

I hope it is not because of Blue. Musk's competition with Bezos could backfire. Either SpX goes for the TKO or Musk has to eat humble pie and get tarred by the MSM.

What's the risk? That the booster crashes? It's already crash landed in the ocean and on the barge. Worst case now is it crashes on an empty expanse of concrete. Why is that any worse?

As for being "tarred" by the MSM, all previous "failed" landing attempts will be forgotten about 5 minutes after the first successful SpaceX landing and Musk will be toasted as the second coming of Werner von Braun, albeit without the unfortunate political baggage.

So I doubt Musk is worried. He's playing the long game, and one or two more failed landing attempts aren't going to prevent an ultimately successful landing.

Which will then immediately eclipse Blue's media coup, since a potentially reusable orbital booster stage is a much bigger deal than a potentially reusable tourist ride.

I don't think the range is worried about it crashing at the landing complex. They are worried about it failing somehow earlier and hitting somewhere else. That's the risk which is all the range deals in. It's coming back fast and from far away so a little mistake in the retro burn could lead to being far off course at the impact point. A few try's getting close to a barge doesn't exactly prove they will do that everytime. And the range is responsible for making sure everyone is safe even when unexpected things happen.

[Coastal Ron]

...my guess is that some pretty heavy arm twisting is in process to go from a barge landing to land and doing so in a brand new launcher that has never flown.

What do you mean by "brand new launcher"?  Other than some minor upgrades it's the same Falcon 9 1st stage that SpaceX has been flying for two years.

[LastStarFighter]

I don't understand what leverage SpaceX could possibly have to twist anyone's arm.

They don't have any; you need to consider the source of the comment.

They don't have leverage. Just influence. Musk is a powerful guy with lots of friends (and fans).

[Kabloona]

I don't think the range is worried about it crashing at the landing complex. They are worried about it failing somehow earlier and hitting somewhere else. That's the risk which is all the range deals in. It's coming back fast and from far away so a little mistake in the retro burn could lead to being far off course at the impact point. A few try's getting close to a barge doesn't exactly prove they will do that everytime. And the range is responsible for making sure everyone is safe even when unexpected things happen.

That's what FTS is for, and Range won't allow an attempt until they're quite comfortable that they've got the right destruct criteria in place and that a destruct command will result in debris falling well away from inhabited areas.

There was a discussion some time ago about possible guidance schemes in which the stage would "target" coordinates well east of the pad, in order to keep the IIP offshore during boostback and braking burn, and then "correct" back to the pad during final descent. That's speculation, but an idea of other ways to mitigate risk in conjunction with FTS.

Bottom line, Range won't allow it until they're convinced the risk is low enough.

[Lars-J]

I don't think the range is worried about it crashing at the landing complex. They are worried about it failing somehow earlier and hitting somewhere else. That's the risk which is all the range deals in. It's coming back fast and from far away so a little mistake in the retro burn could lead to being far off course at the impact point. A few try's getting close to a barge doesn't exactly prove they will do that everytime. And the range is responsible for making sure everyone is safe even when unexpected things happen.

That's what FTS is for, and Range won't allow an attempt until they're quite comfortable that they've got the right destruct criteria in place and that a destruct command will result in debris falling well away from inhabited areas.

Yes, the stage is pretty aerodynamic, like a somewhat blunted arrow. If it breaks up due to FTS, the pieces will fall short of the pad - in the ocean.

[edkyle99]

That's what FTS is for ...

Let's think about flight termination via. explosives.  It works well during propulsive ascent, because the impact point can be stopped from drifting out of a defined acceptable zone.  But how will it work during a descent, which has non-propulsive phases?  If the impact point comes in long during the early portion of reentry, won't blowing up the stage simply result in many more undesired ground impacts?

 - Ed Kyle

[edkyle99]

Re: the "Landing/Launching Complex 1" thing mentioned earlier.  There's info in L2 about a different short-hand name, a pretty cool one, that we're trying to confirm is OK for public discussion.  It's quite clever because it keeps the "Landing Complex" idea while de-conflicting with the old Snark Launch Complex 1 (LC-1) name.

 - Ed Kyle

[Semmel]

If I remember correctly, the stage would land in the water if a burn is missed. Without the re-entry burn and/or the landing burn, the stage is falling in roughly a parabola to the ground. With the landing burn, its trajectory becomes flatter and diverted further land inwards to the pad. So, in case something goes wrong and FTS is triggered, I believe the shrapnel would go into the water off the coast.

[LouScheffer]

I don't understand what leverage SpaceX could possibly have to twist anyone's arm.

I think that a lot of the leverage is philosophical.  NASA at one time was an organization that achieved great things by taking measured risks.  SpaceX now has that reputation, and NASA has an opportunity to get some of it back.  Here we have a potential game-changing advance, with relatively low risk, and NASA will look like overly conservative risk-averse bureaucrats if they turn it down.

[LastStarFighter]

If the impact point comes in long during the early portion of reentry, won't blowing up the stage simply result in many more undesired ground impacts?
 - Ed Kyle

I doubt that's a problem, because the ballistic coefficient of fragments will be lower than that of the intact stage, causing fragments to fall short of the pre-destruct IIP.

Yes, there will be more impact points, but they'll all be short of the pre-destruct IIP. IMHO.

And explosions will add energy to some of the pieces. Especially if it's done far enough above the atmosphere.

[Kabloona]

If the impact point comes in long during the early portion of reentry, won't blowing up the stage simply result in many more undesired ground impacts?

 - Ed Kyle

That's an argument in favor of the idea that they may do a targeting "offset" in which they target coordinates east of the landing pad during the boostback and braking burns, in order to bias the IIP east, then do a final correction with the grid fins during final descent. Only speculation, of course.

[edkyle99]

That's an argument in favor of the idea that they may do a targeting "offset" in which they target coordinates east of the landing pad during the boostback and braking burns, in order to bias the IIP east, then do a final correction with the grid fins during final descent. Only speculation, of course.

OK, what if the boost back burn runs "hot" and then there's a reentry burn, or other failure?  Couldn't this then have a stage plummeting toward someplace like Cocoa or Rockledge, with FTS only able to blast it into many pieces before it hits?

 - Ed Kyle