The oil spill: Your solutions
We asked readers to submit their ideas, external on how the Gulf of Mexico oil spill should have been stopped.
A selection of the hundreds we received has been assessed by Prof Iraj Ershaghi, director of petroleum engineering at the University of Southern California.
BP's cap on the well is currently, according to the company's estimates, capturing more than half of the oil. But could there be a better way?
"Drill a hole next to the well. Place a low-yield nuclear warhead and detonate it.
"The power will fuse the rock together and the intense pressure from the sea water will keep the rock in place thus sealing the leak." - Michael Murray, Greensboro, North Carolina, US
"I think you should create a large fabric tube to help control the amount of oil that gets away from the leak. I think something like parachute cloth might work because that fabric is quite a tight weave - water passes through, but I don't think oil would.
"It might have access panels, especially near the bottom where the actual leaks are occurring, but perhaps that would allow for some kind of pump to pump the oily water that would be held within the tube." - Elaine Seniuk, Enfield, Canada
"How about using small polystyrene beads impregnated with iron filings to cling to the oil, then pick up the beads with an electromagnet which could be mounted on any number of platforms such as vehicles or boats.
"Beads get processed to remove the oil, then re-used. Cheap to produce, easy to collect from water, better than trying to scrape oil off difficult surfaces. Beads would be easily deployable by air/sea." - Alwyn Turner, Chapel-en-le-Frith, UK
"How do we block any hole in the earth? By using the natural resources of the earth itself. I suggest that BP utilise barge after barge of rocks that will sink quickly and directly over the outpouring.
"Enough rocks to create a mini-mountain. Sea bed sand might eventually fill the gaps in the rocks as a kind of cement." - Vernon Turner, St Ives, Cambridgeshire, UK
"Wrap electromagnets at different sections of the pipe and secure. Turn on magnets. Inject small metal material into pipe to be attracted to magnets. As material adheres to inside of pipe, inject slightly larger material. Make sure electromagnets are powerful enough.
"Eventually, the flow will decrease and perhaps stop just like a clogged artery in the human body. Remember, power to the magnets must not stop until the pipe is safely capped." - Anon
"I think that the hole could be plugged to greatly reduce the flow, if not end it, by sinking an old ship over the leak.
"If extra ballast were added to the ship to make it even heavier, it would exert enough pressure to seal the hole." - Howard H Rothman, Bridgeport, Connecticut, US
"What will contain it is simply an enormous funnel in thin mild steel which can be lowered over the whole mess with enough pipe of suitably flexible material and diameter to guide the oil to the surface, where of course it will need a constant supply of tankers to suck/pump it safely aboard.
"Obviously the flow-rate and rate of rise needs to be well estimated to get the diameter of the mile of pipe to the surface." - G Vert Vaughan, Veliko Tarnovo, Bulgaria
"Manufacture a series of 30cm custom plugs, each tapered at the front like a bullet. Each plug must have the same diameter as the inner diameter of the tube (minus 2mm to prevent jamming on the way in). However, along the sides of the plugs, cut 100 small diagonal incisions. Thus the plug will look like it is barbed.
"It will go in easily, but dig itself in when going out, plus the more pressure exerted by the gas, the deeper the plug will dig into the pipe sides. Clearly, the plug must be made of a metal harder than the pipe, or it won't be able to do this. Use a pneumatic or even limited explosive charge to deliver the plugs. I suggest a minimum of two - that's how we seal basement leaks in Canada, after all." - Dave Lundy, Canada
"The most obvious solution to me is to use a bladder that is inserted deep into the pipeline, then pumped up with a high pressure medium. Once the flow has stopped and the feed line removed, the end of the pipe may be sealed by whatever caps are required.
"Alternatively, once the pipe is repaired and if it is to be used again the bladder may be deflated." - Mike Konshak, Louisville, Colorado, US
"Being an ex-plumber, the only way to deal with a pressurised leak is to keep the open end and connect a fitting to the pipe, then shut the fitting when the pipe connection is made. Underwater and at 5,000ft, you would need to use a skirt, fixed to an open-ended pipe. The skirt could be split on one side. This could be drawn down over the broken pipe end and fixed to a sound portion of the broken pipe, away from the break.
"This could be fixed in place using traditional mechanical fittings, but it is not taking the strain yet, as the pressurised stream is going up the new open pipe and through the split skirt. Then you can slowly draw the skirt closed, re-strengthening the fixings on the sound part of the broken pipe, thus allowing the skirt to take more strain of the pressurised flow. The skirt can be drawn to a close, as the fixings are made good behind it and the pressurised stream will flow up the new pipe to awaiting vessels." - Paul, Canada
"To stop the oil flow in the pipe in the Gulf of Mexico, form a funnel that fits into the open pipe and also grips it below the top outside to keep it stable. Pour lead balls of the right size into the funnel to definitely sink into the oil flow despite its speed. They need to be as small as possible while being big enough to be sure to sink. They must be less than about a third of the width of the opening in the funnel to avoid self-jamming in the funnel or pipe and not so large that venturi forces around the balls (from increased oil flow speeds passing the balls) stop them from sinking.
"Reduce the size of the lead balls as the reduced oil flow speed allows smaller ones to sink. When enough lead balls have been fed in to slow down the oil speed, start putting clay balls into the oil pipe. When enough of them have been fed in, put in more lead balls (or steel balls would do by this stage). These last balls will, under the action of gravity, then deform the clay balls to form a seal in the pipe." - Peter Keogh, Olso, Norway
"Could the pipe be crimped shut? I have read that 'giant shears' were used to cut the pipe, so why not 'giant pliers'? Since capping and siphoning seem problematic, crimping, even if not complete and permanent, should diminish the flow at least partially and until the relief wells or other means can ameliorate the situation.
"Once crimping was used it would deform the pipe so that capping or siphoning would be almost impossible." - Julian P Crane, Everett, Massachusetts, US
"Epoxy might be a better top kill method than mud, and in any case a heavier solid is needed - try bismuth and/or iron shot. Delivering the resin and catalyst into the well requires two tubes, though an intermediate pulse of isopropyl alcohol may have a chance or separating the two liquids in a single feed tube, there'd be a risk of simply clogging the feed tube before it reached the well.
"Another alternative plug is a torpedo, wire-guided, with a low speed mode (or restrictor) for manoeuvring into place, and an extended warhead holding just enough charge to split containers of epoxy monomer and catalyst." - Jeremy, New Jersey, US
"Use an umbrella plug, which would be deployed into the well to the point where the drill borehole breached the well, effectively capping from the inside.
"They should drill another hole into the same well and continue collecting the oil. This would diminish the pressure in the currently leaking system, and make it possible to seal the leak.
"If it is possible to hit the current well by drilling into it at an angle, this 'shallow' drill may be faster and easier to do than going all the depth into the reservoir." - Alex, Boston, Massachusetts, US
"It appears that below the cut that they have made before capping the pipe, there is a section of the pipe that is bolted, which combines the two sections of pipe. Wouldn't it be possible to remove the bolts and attach a new section of pipe, bolting the new piece on incrementally, which would allow some leverage in allowing for a rotation of the new section into place.
"The new section could have a valve that could be closed off once this section is put into place, thereby minimising the pressure that they would face when installing this new section." - John Allison, Doylestown, Pennsylvania, US
"To clean up the spill itself they could use a hydrocarbon polymer which attaches itself to oil and produces a sponge-like material which would be easier to clean up, or scoop up.
"They could even dye the polymer so that the resultant material is much more visible and again easier to collect." - Steve, Bermuda
"I know that a lot of wells in the Gulf of Mexico are difficult to produce because of hydrate (methane ice) formation. The containment dome failed because of this. Has the idea of promoting the formation of hydrates within the wellbore itself, to form an ice plug to stop the flow of hydrocarbons, been considered?
"With a reservoir that does not have free water, and producing at above hydrate curve temperatures, the hydrates will not form until the gas has expanded and cooled the surrounding area (Joule Thompson effect). However, if ice cold, fresh water were pumped into the wellbore, perhaps with some ice crystals or grains of sand, or something to promote the seed required to help the hydrate cage form, that may promote the formation of a hydrate plug within the wellbore itself." - Mike, Stony Plain, Alberta, Canada