So we're expecting OCISLY to depart sometime tomorrow (Friday), correct?
I always expect to see the ASDS leave port around the time of a successful static fire, although I think they left port shortly before the successful static fire of ses-9 (but after the start of the scheduled static fire window, IIRC; the static fire came late on the window). I haven't heard anything about static fire timing for this one.
Quote from: John Alan on 04/27/2016 04:44 pmMy humble opinion... The cheapest solution here... is start the ball rolling on the OCISLY barge copy to be built for the upcoming Texas need...And charter much more powerful tugs to do "fast drags" of barges to where they are needed... as needed...Base whole east coast fleet out of Port Canaveral...For Texas launches... drag one down south of Miami and do a small boost forward if need be to reach it...Mix in some RTLS at both pad sites...Job Done... Just my opinion... edit... spellingWouldn't a boost forward increase the re-entry velocity? Heating is critical enough as it is.
My humble opinion... The cheapest solution here... is start the ball rolling on the OCISLY barge copy to be built for the upcoming Texas need...And charter much more powerful tugs to do "fast drags" of barges to where they are needed... as needed...Base whole east coast fleet out of Port Canaveral...For Texas launches... drag one down south of Miami and do a small boost forward if need be to reach it...Mix in some RTLS at both pad sites...Job Done... Just my opinion... edit... spelling
EDIT: Just did some calculations and I'm flat out wrong on anchoring; even with weighted rodes well trimmed for slack, that kind of length would have enough play in it to allow the barge to move by a width or more with even slight changes in current wind, and sea and sea.
Regarding the suggestions to get a larger / faster tug to give faster turnaround on 1 ASDS, two thoughts / suggestions for comment - a) Are multiple tugs an option? Seems like E3 is already at the large end of the spectrum though certainly not the biggest.b) It seems to me that the easiest way to speed up the tugging is to have the ASDS unballasted during towing. IIRC, there is 12' of water in the tanks to enhance stability during landing. Or was it enough water to cause 12' of draft? Whichever way, without ballast the ASDS drafts about 3'. That's a lot less drag and a lot more speed. Is this ballast needed for towing? Assuming that the F9 can handle more rocking motion during tow? If yes to all of the above then fit the ASDS with a built in ballast pumping system.Regarding the proposals for deep sea anchoring - Perhaps that scheme would benefit from having the anchor lines connected to 4 autonomous drone winches?
So if we're talking about manipulating ballast, any merit in having the front of the ASDS ride higher so it would plane easier? I don't know if it's even feasible to speak of getting a barge on plane.. how much more powerful of a tug is needed?
QuoteSo if we're talking about manipulating ballast, any merit in having the front of the ASDS ride higher so it would plane easier? I don't know if it's even feasible to speak of getting a barge on plane.. how much more powerful of a tug is needed?A million-pound barge on a plane? Shirley, you jest.
Quote from: OxCartMark on 04/28/2016 04:18 pmRegarding the suggestions to get a larger / faster tug to give faster turnaround on 1 ASDS, two thoughts / suggestions for comment - a) Are multiple tugs an option? Seems like E3 is already at the large end of the spectrum though certainly not the biggest.b) It seems to me that the easiest way to speed up the tugging is to have the ASDS unballasted during towing. IIRC, there is 12' of water in the tanks to enhance stability during landing. Or was it enough water to cause 12' of draft? Whichever way, without ballast the ASDS drafts about 3'. That's a lot less drag and a lot more speed. Is this ballast needed for towing? Assuming that the F9 can handle more rocking motion during tow? If yes to all of the above then fit the ASDS with a built in ballast pumping system.Regarding the proposals for deep sea anchoring - Perhaps that scheme would benefit from having the anchor lines connected to 4 autonomous drone winches?Mark, IMHO that's an excellent point on ballasting; taking the ASDS out ballasted absolutely increases drag, and thus reduces speed. My question is, do we know whether it's salt or fresh water? If it's salt water, there's IMHO no reason why it would be hard to give the ASDS the capability to self-ballast on location (if it does not already have it). If that ballast water is fresh water (and also the source for the deck water cannons) then it becomes a bit harder, depending on the reasons. If the ASDS holds can't handle salt water due to corrosion concerns, then enabling it to do so would be harder (perhaps as hard as painting the interior with the same sort of paint as used on the exterior underwater areas). As for the water cannon, if those are fresh water, perhaps the ASDS could sortie with only one or two compartments ballasted with fresh water, and the rest empty (to be ballasted on location). Hrmmm. I wonder what the towing speed difference is with an unballasted ASDS vs. a ballasted one? Elsbeth III is small for an oceangoing tug, but not underpowered (5000HP). but the real number we're looking for is bollard pull (the actual amount of force applied via the towline). That varies with tug engine, powertrain, and prop design so it's not a straight conversion from horsepower, but I'm lazy and just looking for a ballpark figure so... turns out Smith Marine has the answer; 50 tons. The tow line is 2 1/4 inch steel, which can easily handle that kind of load. As for the ASDS... we need to calculate drag. So, I'm going to pretend the ASDS is just a barge (the only parts in the water essentially are). I'm way the heck out of my depth (pun intended) here, because I know how to do this for yachts, not barges, so I may be way the heck off. Okay, the two main factors are skin friction and wave (wake) making. Skin friction increases linearly with wetted area (so doubling the wetted hull area via ballasting or loading doubles skin friction) but speed increases drag by the square of the speed. So, doubling the speed doesn't double the drag, it squares it. Therefor, to go faster, you really, really need smaller wetted area vs. more power - so your point about ballasting is spot on; getting rid of the ballast (and halving the wetted area) would have far more impact on potential speed than getting a larger tug with twice the bollard pull. I really should give calculating the actual potential speeds a try, but I need to look up some formulas for that, so I'll need some free time and coffee, neither of which are available to me at the moment. If I can, I'll give it a whirl later.
Next mod to the ASDS... more power... Add a 20,000+hp gas turbine stern drive to the hull...Give the tug a remote control to the powerplant...Tell em to dial it up till it tries to pass you... on edit...I'm kidding of course...
Kabloona is right. It'll be best if you cop to a jesting charge.
Doesitfloat-- Is ballasting with sea water OK?- If the ASDS were easier to tow couldn't the propellers on the tug be changed to be efficient at a higher speed?- What do you think of towing the ASDS unballasted?- Built in ballasting / unballasting system feasible? Rapid?edit: I don't think a Merlin or a 20,000 hp gas turbine would be a productive modification. Look at the drag curve. Need to do something to create a different curve. Thus my inquiry on unballasting.
Quote from: OxCartMark on 04/28/2016 08:32 pmKabloona is right. It'll be best if you cop to a jesting charge.I'll plead ignorance but not jesting. I never jest. Honest. I bet there's a way to get that barge on plane. Just not a practical way.