Protecting recoverable bits from sea water

[nimbus]

<p>Why is it not feasible to have some kind of inflatable system that at least reduces the amount of water exposed to e.g. engine parts? I'm picturing something that'd inflate just before touchdown. Either with air, or with auto-solidifying foam.</p> <div class="Discussion_UserSignature"> </div>

 

[a_lost_packet_]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Why is it not feasible to have some kind of inflatable system that at least reduces the amount of water exposed to e.g. engine parts? I'm picturing something that'd inflate just before touchdown. Either with air, or with auto-solidifying foam. <br /> Posted by nimbus</DIV></p><p>Could you be a little more descriptive in what it is you're discussing?&nbsp; Protecting "what" engines and "why?" </p> <div class="Discussion_UserSignature"> <font size="1">I put on my robe and wizard hat...</font> </div>

 

[nimbus]

Well, everytime I read about sea-landings, it's mentioned that sea water makes reuse difficult. I suppose it means any more vulnerable parts that can't be waterproofed, such as attitude motors.. Am I understanding this wrong? <div class="Discussion_UserSignature"> </div>

 

[kelvinzero]

I have no idea if it is practical, but&nbsp;a quick google of "rocket seawater"&nbsp;finds that someone has tried to patent it

 

[a_lost_packet_]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well, everytime I read about sea-landings, it's mentioned that sea water makes reuse difficult. I suppose it means any more vulnerable parts that can't be waterproofed, such as attitude motors.. Am I understanding this wrong? <br /> Posted by nimbus</DIV></p><p>Ah, rocket motors.</p><p>Well, most conventional anti-corrosion protections against sea-water come in two flavors: Coatings or Design.</p><p>Coatings may not be possible with rocket engine components effected by seawater.&nbsp; They get hot.&nbsp; In other areas, the coatings may be subjected to temperature stresses that conventional materials couldn't tolerate - They'd have to be redesigned from scratch.</p><p>Design changes may not be possible for obvious reasons.&nbsp; Besides the weight that necessary coatings would add, design changes could add a good bit of weight and changing certain critical construction materials may not be possible.</p><p>I'm not sure which engines, exactly, it would be you're talking about.&nbsp; But, not all engines are designed to be re-used.&nbsp; So, that would have to be taken into consideration as well.&nbsp; Just in thinking about it, it would appear you'd need an entirely new engine, built in mind for re-use and sea-proofing.&nbsp; Those might get a bit pricey considering no matter what you end up doing, you have to basically take that engine apart and clean it up (at the least) after every use anyway.</p><p>I'm also not quite sure what a hot rocket motor's (or it's liquid gas "cold" portions) construction materials would do when submerged in seawater immediately after use.&nbsp; The stress on some components might be pretty big.&nbsp; So, ideally, you'd want to keep it out of the water as much as possible.</p><p>How about just putting a ton of parachutes on it, having it hit the ground nose first and putting some stress reduction construction in there for hard-landing on land?&nbsp; Let the body crumple and absorb a good deal of the shock while the engine remains relatively safe for re-work/re-use. </p> <div class="Discussion_UserSignature"> <font size="1">I put on my robe and wizard hat...</font> </div>

 

[j05h]

Boeing (IIRC) did some drop tests of an RS68 variant into water (not sure salt or fresh) with an inflatable cone over the whole nozzle end. It worked well enough that they were talking stage-recovery of Deltas or derivatives. That was maybe mid-90s? <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[a_lost_packet_]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Boeing (IIRC) did some drop tests of an RS68 variant into water (not sure salt or fresh) with an inflatable cone over the whole nozzle end. It worked well enough that they were talking stage-recovery of Deltas or derivatives. That was maybe mid-90s? Posted by j05h</DIV></p><p>So, was the inflatible cone for bouyancy, keeping the motor out of the water for the most part, or did it actually enclose the engine assembly? </p> <div class="Discussion_UserSignature"> <font size="1">I put on my robe and wizard hat...</font> </div>

 

[nimbus]

<p>I mean to do my homework instead of just guessing here, but never remember to when I do have time. I asked the question because everything I've read points to sea landings for re-usable items being ideal except for sea water's detrimental effects. I don't remember what parts it was a problem for specificaly, or if it was a problem for all parts in general.</p><p>&nbsp;I think it's at the selenian boondocks (sp?) blog that someone recently mentionned something of a composite of what's described above, a nose down splash with bouyancy set up to keep the engine out of water (this for a Falcon first stage IIRC).&nbsp; My inflatable (and/or foam for better seal) suggestion was mostly to find out from the pros here why it wasn't feasible, which I assumed it wasn't -&nbsp;given the (again assumed) fact that sea landings are better (except for sea water corrosion) and yet one of the most obvious solutions was never used.</p> <div class="Discussion_UserSignature"> </div>

 

[vulture4]

While recovery at sea is possible, it isn't usually viable if the equipment must be overhauled after each flight. Ocean-going vessels are constructed very differently from aircraft, and much more heavily. I see no evidence that recovering either the Ares booster or the Orion capsule for reuse is economically rational. Recovering a liquid-fueled booster might be feasible if it was designed to tolerate salt-water immersion and ruse without complete disassembly, but no one has demonstrated this yet. SapceX would have the best chance as the Falcon first stage is lighter and easier to recover by parachute and ship, but if there is any damage an overhaul is still required. I feel ultimately a winged vehicle with land recovery is more practical.

 

[nimbus]

So the cost in weight for something that'd shield the recovered stage(s) outweighs the savings from re-using a clean sea-landing stage.