Disclaimer: this idea is coming from someone (that would be me) who has next to NO real understanding about the technology involved with this whole endeavor, and may appear to be silly, or even laughable, to someone with a clue. But with that said:
Why not dispense with the whole platform/barge/soft landing thing and just drop it in the water - with huge floats that inflate/engage on impact to keep it from sinking? Then just come along with a ship and a crane, scoop the thing out of the water, towel it off and you're good to go for another flight? Seems a WHOLE lot easier to accomplish, cheaper, less risk of things going wrong, etc. Heck, I bet we could modify a Rouse-Tech CD3 system with a couple extra cartridges to do the job.
OK, I'm obviously being just a bit tongue-in-cheek here, but is something along these lines at all possible? I would think that corrosion due to salt water immersion would be a big problem (and one that could not be overcome?), but I would also think that salt air and salt spray would then already be an issue with the current scheme. ANYTHING that sits outside on a ship/barge at sea gets a whole lot of salt on it without ever touching the water, but there are hundreds of years of marine experience/know-how to deal with this in both high and low tech ways. If Elon can build something that survives space flight, I'm sure he could figure out a way do deal with a bit of salt water.
s6
The Saturn team under Von Braun looked at doing this sort of thing back in the 60's... over in the scale section of the forum, I've done "study summaries" of a number of these sorts of things... complete with pics. They looked at everything from "glideback" S-IB first stages flying back to land using Rogallo flex wings deployed after staging and deceleration, to parachute landings in the ocean and subsequent recovery. At one point there was even a plan developed to potentially partially reuse Saturn V first stages (S-IC stages) via water recovery, having them parachute nose-first into the ocean, and severing the forward tank dome of the oxygen tank via linear shaped charge explosives to create a "cushion" for the water landing (the tankage was considered expendable-- they wanted to recover the F-1 engines intact, which were the most expensive and complex part of the stage anyway). They even did experiments, dunking an H-1 engine into salt water, leaving it there for IIRC about 24 hours, fishing it out, and then treating it to a wash-down, with appropriate delays built in to simulate recovery times required, rebuilt it, and then test fired it again in a test stand, quite successfully in fact. What it boiled down to in the end is that NASA neither wanted to spend the time or money to make recovery of the first stages of the Saturn V or Saturn IB a reality, thus this work never proceeded past the proposal and experimentation phase. It wasn't necessary to the overarching goal-- putting a man on the Moon before the Soviets, so it simply wasn't a priority. By the time that had been achieved, there was no money to do it and NASA organizationally was looking to move on to a "fully" reusable system in shuttle (as it was proposed at the time, with a liquid propellant flyback and landing first stage and orbiter).
During the shuttle development, and in proposals for advanced boosters during the shuttle era (and other improvements) there were proposals for reusable liquid-propellant boosters, some using a cluster of four SSME's each, some using varying numbers and types of other liquid propellant rocket engines. These were to be housed in sealed "boattails" at the base of the boosters, equipped with closing, water-tight "petals" or "shutters" that would unfold and cover the base of the boattail (and the engine bells within it) so they could splash down under parachute into the ocean, and simply lay over on their sides and bob there in the swells, awaiting retrieval and towing back to KSC for refurbishment and reuse. These systems were never really tried (that I've found anyway) and were considered at best complex and potentially unreliable, to somewhat fanciful in terms of their practicality and effectiveness to stand up to real world conditions of an ocean splashdown. By that time, NASA had some experience with "reusable" components (shuttle boosters) that splashed down at sea and were immersed in salt water for extended periods, and knew the difficulties and expense of refurbishment in terms of actual costs, even for relatively "simple" systems like the APU's and nozzle vectoring hydraulics, avionics, etc. contained in the SRB boattails, as well as elsewhere on the shuttle SRB's (forward compartment). That's why "ocean splashdown reusability" wasn't really embraced as a desirable method of operation for any further 'reusable' components. It also became known after the shuttle program completion that basically, it cost SO much to recover the SRB's from the water and to refurbish its operating systems and components and test and reintegrate them into another launch-ready SRB, that it would have been cheaper to actually build ALL-NEW SRB's after each flight than to recover them, at least using the operational methods as the SRB's were designed. It's also worthwhile to consider the sheer forces acting on these things when they actually splash down... the reusability of the SRB's came to an end for Ares I/V and SLS after the SRB-X flight, where the existing shuttle casing (with a fifth "dummy segment") landed SO hard (due to the extra weight and the partial shredding of its parachute system) that the case was bent/flattened beyond repair or reuse by the water landing-- now that's a 146 inch (just over 12 feet diameter) casing made of 1.5 inch thick solid steel, in the case of the SRB... now imagine a LIQUID rocket stage plunging into the ocean under parachute, made of ALUMINUM or Aluminum-Lithium alloy that's only anywhere from maybe 1/4 inch thick (at the bottom end) to 1/16 inch thick or less (at the upper end) and 10-12 feet across or more... it's going to be hard for it not to crush like a beer can under it's own weight due to the impact forces, or fold in half... and how do you trust a structure that delicate after plopping it into the ocean under parachute (which is anything but gentle) not to fail when filled with the weight of tens to hundreds of thousands of gallons of propellants at anything from room temperature to -291 degrees F (for LO2), pressurized to 40-60 PSI (head pressure in the tank), and carrying the weight of tens of thousands of pounds of upper stage structures, interstage(s), and payload above it?? (a liquid rocket structure is, for all intents and purposes, essentially a big aired-up tire in terms of how the load bearing part works). Now imagine that load being multiplied by 3-4 times or more during ascent acceleration, with the additional pressure of thousands of pounds of force exerted on the vehicle and payload fairing during launch through max-q, vibration, effects of cryogenic temperatures on metals in the tank walls, and now throw in possible salt water corrosion... One dent, one unseen crease or kink lets go, the whole thing rips apart or blows up. THAT is why "splash down" LRB's were generally discarded as a viable reusability method... If you're talking about SRB's or PRESSURE-FED LRB's (using lower efficiency pressure-fed liquid burning booster engines, but requiring SRB-like heavy, thick-walled tanks to contain the propellant and pressurize it to hundreds or thousands of PSI to inject it into the combustion chamber of the rocket engine directly without turbopumps) then we KNOW that is *possible*, but it's not particularly beneficial or *practical*, and certainly not *desirable*.
This is part of what shuttle manager John Shannon called "the myth of reusability" in his testimony before the Augustine Commission back in 2010 (IIRC). Shuttle cost SO MUCH to reuse due to the high amount of refurbishment work and the expense of it that was necessary, that it was basically just as cheap, if not cheaper, to simply throw everything away and build all-new parts for subsequent launches-- this was true of the SRB's and the SSME's, if not the orbiters and SRB casings themselves (which is debatable). That is why the SLS will use the existing SRB shuttle casings one final time-- and drop them back into the ocean without parachutes, where they'll smash to bits or flatten like pancakes when they impact the water at ~250 mph and sink to the bottom of the Atlantic... and once the existing supply of shuttle-era booster segments is used up, NASA will have to develop all-new EXPENDABLE rocket boosters to take their place-- either the ATK "Black Knight" carbon-filament-wound composite advanced SRB's, or the F-1B kerosene engine powered Dynetics "Pyrios" boosters... NEITHER will be reusable, and new ones will simply be built for every flight. That's why NASA even sold off one of their two SRB recovery ships, and converted the other one into a camera ship for photography of launches from out at sea...
Elon and the space community at large has learned these lessons, hopefully, or at least observed them. They know that for reusability to actually be WORTH THE EXPENSE, you MUST have the rocket stage return in as GOOD A CONDITION AS POSSIBLE, requiring AS LITTLE REPAIR/REFURB POSSIBLE and the LOWEST AMOUNT OF TURNAROUND POSSIBLE in order to reliably and safely relaunch using it. That was what KILLED shuttle-- NASA *purposely* under-estimated the amount of refurbishment and turnaround required between launches of not only the orbiter and SSME's, but also the SRB's and the system as a whole, while simultaneously VASTLY underestimating the cost required to perform that refurbishment and preparation work, as well as MASSIVELY overestimating the flight rates and "demand" for shuttle launches, to spread those costs over an enormous number of launches that was never going to happen anyway. That's how the shuttle was sold-- with wild estimates of it flying up to 70 times a year with per-flight costs of only as little as $10 million dollars each (in the wildest of the 'estimates' NASA touted). Even when "reality" set in (as NASA saw it) in the later 70's, they still wildly overestimated shuttle's flight rates and underestimated its refurbishment costs... it was advertised as flying about 50 times a year (basically, weekly) at a cost of about $35 million per flight. The SSME's original design specifications called for them to be reused up to 100 times WITHOUT OVERHAUL. This was later lowered to 50 flights. In practice, EVERY SSME was TOTALLY stripped and rebuilt after every flight-- parts that could not be taken apart (welded together) had to be laboriously inspected with bore-scopes to ensure that no cracking or damage had occurred (and oftentimes damage and cracks WERE found) so in the end, every shuttle engine had to be completely rebuilt after every flight, and test-fired at Stennis Space Center before being sent to the Cape for use on future shuttle flights. This made the SSME's nearly as expensive to refurbish as to replace outright with new engines, especially if one considers the savings from mass production (SSME's were extremely expensive because they were produced only in very small batches a few engines at a time, and were extremely complex and very high performance... had they been designed simpler and cheaper and produced "in bulk orders" and thrown away, they should have been much cheaper to produce and cost much less than rebuilt reusable SSME's (which is exactly what they're planning to do on SLS... course the flight rate on SLS is going to be SO pathetically low (1 flight every 2-3 YEARS) that these 'mass production" savings may well never materialize... )
Anyway, for reusability of the Falcon 9 to ever make sense, the thing has to land INTACT, in OPERABLE CONDITION, and require only basic service, testing, and checkout before being sent for integration into a new launch vehicle. If it requires extensive salt-water impingement mitigation (beyond a good pressure washing), large amounts of complex touch-labor inspection, refurbishment, testing, and turnaround before it can be reused, it would QUICKLY surpass the expense of simply replacing the stage with an all-new one and foregoing the expense and complexity of actually recovering the stages and refurbishing them for reuse.
Later! OL JR
