I'm having a hard time understanding how SpaceX is being prohibited from doing an RTLS on the upcoming SSO-A flight. Looking at the map, Launch Complexes 4 and 6 are 3.7 miles apart while Landing Zone 4 is 0.3 miles from Complex 4.The following have to be true1) If a nearly empty 1st stage crashing at LZ-4 can cause damage at LC-6, it will obliterate LC-4. But SpaceX put it there, and crashing 1st stages didn't destroy drone ships.2) If a crash at LZ-4 can damage LC-6, then a fully fueled F9 explosion (AMOS-6) will cause orders of magnitude more damage. 3) The 1st Stage flies directly back to the landing site. With LZ-4 and LC-4 being so close, if the returning stage has to overfly LC-6, then so does the fully fueled F9 only seconds after launch where it could drop directly onto LC-6 if any failure occurred.4) If the launch doesn't have to overfly LC-6, the landing doesn't have to either.5) If a crash at LZ-4 will cause brush fires that destroy the base, so will a failure at LC-4, or LC-6 for that matter.Therefore, if SpaceX is allowed to fuel and launch F9 with Delta IV-H at LC-6, they should be allowed to land there. How does this make any sense?
Quote from: Norm38 on 11/14/2018 04:57 pmI'm having a hard time understanding how SpaceX is being prohibited from doing an RTLS on the upcoming SSO-A flight. Looking at the map, Launch Complexes 4 and 6 are 3.7 miles apart while Landing Zone 4 is 0.3 miles from Complex 4.The following have to be true1) If a nearly empty 1st stage crashing at LZ-4 can cause damage at LC-6, it will obliterate LC-4. But SpaceX put it there, and crashing 1st stages didn't destroy drone ships.2) If a crash at LZ-4 can damage LC-6, then a fully fueled F9 explosion (AMOS-6) will cause orders of magnitude more damage. 3) The 1st Stage flies directly back to the landing site. With LZ-4 and LC-4 being so close, if the returning stage has to overfly LC-6, then so does the fully fueled F9 only seconds after launch where it could drop directly onto LC-6 if any failure occurred.4) If the launch doesn't have to overfly LC-6, the landing doesn't have to either.5) If a crash at LZ-4 will cause brush fires that destroy the base, so will a failure at LC-4, or LC-6 for that matter.Therefore, if SpaceX is allowed to fuel and launch F9 with Delta IV-H at LC-6, they should be allowed to land there. How does this make any sense?The primary issue is probably the very expensive payload at SLC-6. If there was an equivalent payload being mated to a F9 insice the LC-4 hangar, they would not allow a landing just outside.As far as the difference during launch vs landing, they perceive that a launch as more active control and can be terminated more effectively... versus a landing stage that can malfunction fall dead "anywhere". Is it a valid concern? Maybe, maybe not. But it will take many landings for them to feel more confident about it.
During launch, the IIP lingers a lot longer, the vehicle is 100x as dangerous, and an abort buys you relatively little.
During return, the IIP is on the landing site or beyond, the vehicle is empty, and not only is an abort really effective, but by default the vehicle can be made to overshoot or otherwise miss by a large margin.
Quote from: meekGee on 11/14/2018 10:34 pmDuring launch, the IIP lingers a lot longer, the vehicle is 100x as dangerous, and an abort buys you relatively little.No. During the launch the IIP moves quickly across LC-6. Not so during boost-back, as the IIP is fairly wide and lingers after the boost-back burn is complete. (see below for more detail)Quote from: meekGee on 11/14/2018 10:34 pmDuring return, the IIP is on the landing site or beyond, the vehicle is empty, and not only is an abort really effective, but by default the vehicle can be made to overshoot or otherwise miss by a large margin.No. At least for CCAFS, the boost-back burn puts the IIP short of the landing site (ocean), and the grid fins steer it past the landing site, and the final landing burn targets the landing spot. This was pretty conclusively shown during the FH booster landing discussions on this forum. So the IIP keeps moving back and forth.And your "can be made to" phrase assumes a vehicle that you do not lose control of.
Quote from: Lars-J on 11/14/2018 11:47 pmQuote from: meekGee on 11/14/2018 10:34 pmDuring launch, the IIP lingers a lot longer, the vehicle is 100x as dangerous, and an abort buys you relatively little.No. During the launch the IIP moves quickly across LC-6. Not so during boost-back, as the IIP is fairly wide and lingers after the boost-back burn is complete. (see below for more detail)Quote from: meekGee on 11/14/2018 10:34 pmDuring return, the IIP is on the landing site or beyond, the vehicle is empty, and not only is an abort really effective, but by default the vehicle can be made to overshoot or otherwise miss by a large margin.No. At least for CCAFS, the boost-back burn puts the IIP short of the landing site (ocean), and the grid fins steer it past the landing site, and the final landing burn targets the landing spot. This was pretty conclusively shown during the FH booster landing discussions on this forum. So the IIP keeps moving back and forth.And your "can be made to" phrase assumes a vehicle that you do not lose control of.Remember the Antares failure? If you count seconds, not to mention risk-seconds, not to mention risk-damage-seconds - launch is worse.
Quote from: meekGee on 11/14/2018 11:54 pmQuote from: Lars-J on 11/14/2018 11:47 pmQuote from: meekGee on 11/14/2018 10:34 pmDuring launch, the IIP lingers a lot longer, the vehicle is 100x as dangerous, and an abort buys you relatively little.No. During the launch the IIP moves quickly across LC-6. Not so during boost-back, as the IIP is fairly wide and lingers after the boost-back burn is complete. (see below for more detail)Quote from: meekGee on 11/14/2018 10:34 pmDuring return, the IIP is on the landing site or beyond, the vehicle is empty, and not only is an abort really effective, but by default the vehicle can be made to overshoot or otherwise miss by a large margin.No. At least for CCAFS, the boost-back burn puts the IIP short of the landing site (ocean), and the grid fins steer it past the landing site, and the final landing burn targets the landing spot. This was pretty conclusively shown during the FH booster landing discussions on this forum. So the IIP keeps moving back and forth.And your "can be made to" phrase assumes a vehicle that you do not lose control of.Remember the Antares failure? If you count seconds, not to mention risk-seconds, not to mention risk-damage-seconds - launch is worse.For the launch pad where the rocket is launched, yes. But not for LC-6 from an LC-4 launch. Once the IIP reaches LC-6 it passes quickly.
I'd feel much safer at LC-6 during the return leg, where there's a passive divert safeguard, plus am effective FTS option. Neither of these is effectively available during launch, the fuel load is much higher, and so is the risk of failure (higher energies, higher stresses).
Quote from: meekGee on 11/15/2018 12:58 amI'd feel much safer at LC-6 during the return leg, where there's a passive divert safeguard, plus am effective FTS option. Neither of these is effectively available during launch, the fuel load is much higher, and so is the risk of failure (higher energies, higher stresses).What? Are you not familiar with all the trouble SpaceX (and all other launch provider) go through to create a fool proof FTS system for the launch??
Quote from: Lars-J on 11/15/2018 01:14 amQuote from: meekGee on 11/15/2018 12:58 amI'd feel much safer at LC-6 during the return leg, where there's a passive divert safeguard, plus am effective FTS option. Neither of these is effectively available during launch, the fuel load is much higher, and so is the risk of failure (higher energies, higher stresses).What? Are you not familiar with all the trouble SpaceX (and all other launch provider) go through to create a fool proof FTS system for the launch??I have never heard of a fool proof FTS system... Not even close.
Failure near launch will always result in a fiery shit storm on the ground below, the FTS can only try to diminish it.
Quote from: meekGee on 11/15/2018 01:24 amQuote from: Lars-J on 11/15/2018 01:14 amQuote from: meekGee on 11/15/2018 12:58 amI'd feel much safer at LC-6 during the return leg, where there's a passive divert safeguard, plus am effective FTS option. Neither of these is effectively available during launch, the fuel load is much higher, and so is the risk of failure (higher energies, higher stresses).What? Are you not familiar with all the trouble SpaceX (and all other launch provider) go through to create a fool proof FTS system for the launch??I have never heard of a fool proof FTS system... Not even close. How many FTS systems (for US launch providers) have accidentally been triggered? How many FTS systems have failed to work when they needed to? I can't think of any... But feel free to correct me. That's pretty impressive statistics for a set of bombs strapped to rockets controlled by radio signals.Quote from: meekGee on 11/15/2018 01:24 amFailure near launch will always result in a fiery shit storm on the ground below, the FTS can only try to diminish it.Obviously. But the discussion is about dangers for LC-6, not the launch pad itself. That's how this discussion got started. For LC-6, launch has a high damage potential for a short time (as the IIP passes over/near), for landing it is lower damage potential for an extended time (all the way from end of boost-back to landing). Danger that they do not have sufficient experience with to quantify accurately. As confidence in SpaceX's booster landings grow they will worry less and less.
So in practically every aspect, being on LC-6 during the return leg is safer, by a lot, then during the outbound leg.
Quote from: meekGee on 11/15/2018 01:47 amSo in practically every aspect, being on LC-6 during the return leg is safer, by a lot, then during the outbound leg.Sez you. I have $xxxxM mission on the pad and you want to add $xxxM risk to my mission that will benefit you $xxM and that will cost you $xM for risk avoidance and benefit me how? You want to go for it, fine, but be prepared to pay the insurance premiums (likely unavailable at any price); if you can't get any takers, then go fish, which is likely what they did.Occam's razor: They did the math and crunched the financials and no one is willing to take that bet. So they went with the $xM risk avoidance option (droneship landing).
Even if you want to argue that the added risk is minuscule, no matter how small the added amount of risk, when you divide by the 0 benefits*, you get infinity.
If you had to be at the LC-6 for one leg OR the other, from a safety perspective, which would you choose.
Not to start a whole side argument, but does the computer really care what coordinates are selected for the landing site, whether land or sea? Isn't landing experience cumulative and not site specific?