and you need to put nose cap on top if it is not side FH booster, where it already installed. with other activities related to rapid reflight such as refueling, folding legs, using hold downs and possible abort launch you need some mobile launch platform which could catch and rotate horizontally whole booster. its weight after drain RP will be less then 20 tons. not big deal.so in this cas reflight will look like:1. land on droneship2. drain lox3. move mobile launch platform from support ship to drone ship (or where it will be)4. secure booster with platform. fold legs5. move whole thing and then rotate horizontally6. check all you need, install nose cap, fuel tubes and all other needed for launch.7. put it vertical, refuel and launch with possible abort.
However, keeping pretty big volume of LOX and RP-1 where hot rocket is coming in is a pretty dangerous proposition. Ensured loss of barge in cases, similar to SES9...
One potential issue with "gas and go" from the drone ship is that you don't have hold down clamps. You also have no payload, so the stage is relatively light - even when fuelled - that means even partial engine thrust will possibly give you >1.0 thrust2weight (depending on how many engines are used)
Different flight profiles require different landing coordinates.
Aerodynamic stability would make flyback difficult. You need to maintain powered flight in the atmosphere to maintain control, and keep dynamic pressure low so you don't need a nosecone, and to limit fatigue cycles on the airframe. But you do need to go exoatmospheric in order to flip add accelerate for crossrange. So you need to ballast for ascent and probably do staged shutdowns as you burn fuel to keep t:w near 1, then throttle up once exo to get ballistic crossrange, then flip the stage and deploy fins for reentry. Additionally you need to constrain the terminal ballast so as not to crush the legs when you land. It seems like an overconstrained problem which may not be tractable without a nosecone or some provision to precision-dump propellants during exo coast.
In his first “drone ship” tweet, Mr. Musk held out the tantalizing possibility that the drone ships would eventually allow recovered stages to be refueled, launched from the deck, and fly themselves home. Time will tell if SpaceX can make this dream a reality.
I agree that launch back is no mean feat.You'll launch with 2-3 engines and very partial fuel load. Stability should be OK since you're under power.
What might SpaceX be doing to protect the booster from salt spray? A tarpaulin around the engine area, or perhaps a spray coating that could be removed easily with no residue? An exposure of several days might not be an immediate issue, but many such might have a cumulative effect.
Quote from: meekGee on 04/10/2016 02:56 pmI agree that launch back is no mean feat.You'll launch with 2-3 engines and very partial fuel load. Stability should be OK since you're under power.A question on reliability then: Assuming it's the same 2-3 engines that are used for the landing burn, presumably that means those 2-3 engines will wear out faster than the other 6-7 and require earlier swap-out. Doesn't having engines with significantly different run-hours decrease the reliability of the re-used stage on the way back up??Quote from: pmonta on 04/10/2016 04:45 pmWhat might SpaceX be doing to protect the booster from salt spray? A tarpaulin around the engine area, or perhaps a spray coating that could be removed easily with no residue? An exposure of several days might not be an immediate issue, but many such might have a cumulative effect. I don't see there's anything they can do about it, aside from the usual acid-anodising during manufacture and a fresh-water hose down. A tarpaulin might actually make things worse by concentrating salt water exposure in a few particular areas.
Engine usage could be evened out by alternating between two groups of 4 engines in the outer ring of the octo-web. Alternate these for each launch and everything will be getting similar utilization.
Quote from: Impaler on 04/11/2016 07:40 amEngine usage could be evened out by alternating between two groups of 4 engines in the outer ring of the octo-web. Alternate these for each launch and everything will be getting similar utilization.Especially if they can manage to pull off two-engine landing burns reliably.Would the first stage really need to go exoatmospheric?