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

[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

OK, the shorthand name for the landing complex at Cape Canaveral is "X1", but we're not sure it is an official name just yet.  It may be a mesh of "Landing CompleX 1" while also referring to "SpaceX".  Kinda neat I think.

 - Ed Kyle

[Chris Bergin]

Certainly cool and very SpaceXey, but as noted one has to wait for SpaceX's main press officer (Elon on Twitter ) to name things.

Also as noted, it's a bit like how we (and other sites) know what BFR means, but that's not an official name. SpaceX say "MCT" for the whole show on that monster.

[Kabloona]

The system will know to a high degree of accuracy where it is going to land once engines are off.

No, it won't.

The guidance system simply targets a set of landing coordinates and possibly some waypoints along the return trajectory, and does its best to hit those points. If the engines shut down unexpectedly, the flight computer would still be sending out guidance signals trying to keep the stage on trajectory, and it would still be trying as the stage crashed into the sea. It's not calculating where it's going to crash land, it's calculating what commands to send to the engines and ACS in order to get where it wants to go.

If you asked the flight computer, "where will you hit the ground if the engines stop running now?" it won't be able to answer the question. All it can tell you is (1) current state vector (where it is now, velocity, etc) and (2) how close it is to the desired trajectory.

Calculating where it will land (IIP) is the job of Range radars and computers, and there's no point in duplicating that effort onboard.

It's similar to the principle of an aborting cargo Dragon capsule leaving an exploding stage, had it had the right software to enable a parachute deploy, it could have been 'saved'. And they are going to put in software for that very circumstance.

How is the stage going to save itself by shutting down its engines prematurely to avoid an FTS destruct command? It will still crash and be destroyed. And there aren't going to be any parachutes.

[abaddon]

I was hoping for LX-1 myself.  The "X" part seemed obvious .

[gadgetmind]

Hmm, maybe not XL5 given the "Fireball" connotations!

(Hit google/wikipedia if too young!)

[CyndyC]

Anyone interested in an RTF viewing event organized by PRI Productions in Jacksonville and their producer who is a licensed aviator, please PM me. It has not yet been decided if this will be a local audiovisual event or a chartered bus to the Cape.

[joek]

No need for FTS if they just shut off the engine - that solves the "many pieces" problem.  And they can do that at any point it deviates from the safe passage corridor.

What you are describing would be allowed only if it is within an allowed flight path (edit: and the IIP at thrust termination was within the allowed flight path).  If it deviates from an allowed flight path, FTS is activated.  FTS requirements are clearly defined:

D417.3   Flight termination system functional requirements

(a) When a flight safety system terminates the flight of a vehicle because it has either violated a flight safety rule as defined in §417.113 or the vehicle inadvertently separates or destructs as described in section D417.11, a flight termination system must:

(1) Render each propulsion system that has the capability of reaching a populated or other protected area, incapable of propulsion, without significant lateral or longitudinal deviation in the impact point. This includes each stage and any strap on motor or propulsion system that is part of any payload;

(2) Terminate the flight of any inadvertently or prematurely separated propulsion system capable of reaching a populated or other protected area;

(3) Destroy the pressure integrity of any solid propellant system to terminate all thrust or ensure that any residual thrust causes the propulsion system to tumble without significant lateral or longitudinal deviation in the impact point; and

(4) Disperse any liquid propellant, whether by rupturing the propellant tank or other equivalent method, and initiate burning of any toxic liquid propellant.

(b) A flight termination system must not cause any solid or liquid propellant to detonate.

(c) The flight termination of a propulsion system must not interfere with the flight termination of any other propulsion system.

[vulture4]

SFAIK SpaceX still uses the DOD-compliant booster-destruct FTS, although the FAA allows a little more flexibility, so they would have the option of destroying the booster with all the fragments falling within a limited footprint. Also, for launches there is always a significant area around the pad that is cleared of personnel, and a larger area where only essential personnel are permitted. Presumably this will be done for landings also, so there is some margin for potential ballistic impact points to be beyond the boundaries of the concrete pad during the approach without requiring flight termination. I would imagine the FTS protocols will be similar to those used during a launch, since the potential for the rocket going off course is always considered. In terms of the actual potential damage, with only one stage and most of the fuel expended, the potential explosive effect (and the dispersion of fragments) would be only a fraction of what might be seen on a launch. Personally, having seen what sea motion can do off the Florida coast to even a large ship, I am all for landing on land instead. Often the launch weather with Shuttle was fine but the weather in the booster recovery area was considerably worse.

With the exception of possibly recovering the core stage of an FH launch at a downrange distance where a return to land is not feasible, I don't see any particular reason to use the barge again.

[CyndyC]

Going back a bit, how far offshore would a barge need to be stationed before you don't need launch range approval to land there?

SpaceX could test the vast majority of flyback and still land a couple or more miles off shore.

I don't know if I they could get any closer w/o approval, but for more than one effort the local news in Jacksonville has reported the barge was 200 miles offshore.

[CraigLieb]

RE:  proposed timing of the landing at LC1 for this launch

I am wondering if the successful "Land" landing of the Blue Origin rocket might help the decision to green-light SpaceX for a landing?  Could an element in some Risk Matrix that changes rankings because somebody (ANYBODY) has now landed a stage from space (not orbit, but space at least)?

In this way, maybe without realizing it, BO success could have opened up the theater of the possible in the mind of the general population. We know that of course NASA is more sophisticated, and may discount the BO event due to the severe nature of the differences in the rockets, the speeds, the location of the landing, etc. 

thoughts?

[joek]

SFAIK SpaceX still uses the DOD-compliant booster-destruct FTS, although the FAA allows a little more flexibility...

FTS standards have been harmonized (at least at higher levels).  The FAA's are codified in CFRs; DOD and NASA standards can be found in the Flight Termination Systems Commonality Standard, Range Commanders Council Range Safety Group, September 2014.

[vulture4]

AIUI the approval process was already in the works, and SpaceX has had no difficulty hitting the target on every attempted return, they have just hit a little hard, which isn't really a safety issue. However the BO flight puts BO on the fast track for carrying suborbital tourists on a ride past the von Karman line, and seems to leave little room for Virgin to compete for that market.

joek - thanks for the link. This is interesting: "Shutdown and/or parachute systems may be used in lieu of rupturing propellant tanks if the risk posed by an intact impact is acceptable."

[ugordan]

It's not NASA that makes this call, AFAIK, but USAF and FAA. The hardware is sufficiently different and the risks to general population higher with a Cape landing so I think the BO success had little to no bearing on any SpaceX landing attempt approval. The Range might have OK'd it long before BO for all we know.

[abaddon]

With the exception of possibly recovering the core stage of an FH launch at a downrange distance where a return to land is not feasible, I don't see any particular reason to use the barge again.

You may not, but SpaceX disagrees with you.  They've specifically noted that the FT version will enable booster recovery downrange for the single-stick version with GTO launches.

[Kansan52]

Another way that a Blue successful landing might influence the decision is strengthening the pro-land constituency inside NASA, AF, and FAA.

[joek]

Going back a bit, how far offshore would a barge need to be stationed before you don't need launch range approval to land there?

SpaceX could test the vast majority of flyback and still land a couple or more miles off shore.

I don't know if I they could get any closer w/o approval, but for more than one effort the local news in Jacksonville has reported the barge was 200 miles offshore.

Still need approval for landing-entry-whatever, regardless of where.

[vulture4]

With the exception of possibly recovering the core stage of an FH launch at a downrange distance where a return to land is not feasible, I don't see any particular reason to use the barge again.

You may not, but SpaceX disagrees with you.  They've specifically noted that the FT version will enable booster recovery downrange for the single-stick version with GTO launches.

I see, wasn't aware of that. They may have some scrubs for offshore weather.

[Jim]

Another way that a Blue successful landing might influence the decision is strengthening the pro-land constituency inside NASA, AF, and FAA.

There is no such constituency either way in NASA.
And why would it change the AF or FAA?  Barge attempts and McGregor testing is no different.

[Kansan52]

Another way that a Blue successful landing might influence the decision is strengthening the pro-land constituency inside NASA, AF, and FAA.

There is no such constituency either way in NASA.
And why would it change the AF or FAA?  Barge attempts and McGregor testing is no different.

I can agree that Blue's success may not influence decisions. But I cannot agree that are no constituencies in the various organizations.

[rcoppola]

Another way that a Blue successful landing might influence the decision is strengthening the pro-land constituency inside NASA, AF, and FAA.

There is no such constituency either way in NASA.
And why would it change the AF or FAA?  Barge attempts and McGregor testing is no different.

I can agree that Blue's success may not influence decisions. But I cannot agree that are no constituencies in the various organizations.

Shotwell stated many months ago during one of her interviews that the USAF was showing great interest and support for their land landing aspirations. Nobody is trying to block them and the key players are supportive, this is about risk and safety only....which is as it should be. After all, they have now been leased two launch pads and rebuilt them as landing complexes. That in and of itself is a very clear indication of support.