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Comment Re:Wou would have thought. (Score 3, Interesting) 50

Basically you need a third object to get involved, for instance it's thought that Triton was one of a pair of similar sized objects in orbit around each other. Triton was (relatively) going backwards at the time of a close approach so landed up in orbit around Neptune, it's partner got slung away. That also seems to explain why Triton is in a retrograde orbit.

Comment Re:What is the purple stuff? (Score 3, Informative) 69

The liquid is a camera inside the second stage fuel tank, last launch they were showing it after the engine cut-off and you had large blobs of the stuff floating round inside. The black and white camera appears to be a thermal infra-red looking at the second stage engine nozzle.

Comment Re:Right .... (Score 1) 523

And the RTG itself isn't all you need. You need decent sized radiators to dump the excess heat for a start.

An RTG would have eaten somewhere between a third and half the mass available for science instruments, and you'd have quite a lot of excess heat being dumped into the surrounding environment which would distort the readings being returned.

Comment Re:Decisions, Decisions... (Score 3, Interesting) 123

It's what SpaceX are currently calling the BFR will switch to Methane instead of Kerosene. The Falcon Heavy is effectively three Falcon 9 stages in parallel, similar to the existing Delta IV Heavy but with added fuel cross-feed. With cross-feed the core stage will still be fully fueled when the boosters detach.

Methane has the advantage it doesn't need the tank to be pressurised with Helium, a bit of excess heat can be diverted back into the tank to boil off enough to keep the pressure up. The current Helium pressurisation has been giving problems and accounted for a few launch delays because of leaks. The tank needs to be bigger, but overall complexity drops.

Comment Re:GPS on Mars (Score 1) 104

As a proof of concept running a quadcopter is a lot easier, but for an actual Mars landing it wouldn't be too difficult to build one with rockets instead of rotors. Hobbyist quadcopter autopilots will run a wide variety of motors with a few tweaks to parameters, rotors to rockets is a larger step but not beyond the realm of a reasonable software project.

Comment Re:Excuse the pedantry... (Score 2) 90

What counts as the start and end point of an EVA varies depending on what Agency is reporting it and who wrote the press release. The start can be anything from the start of decompression, reaching vacuum, opening the hatch or stepping outside, and the end stepping back in, closing the hatch, starting recompression or returning to atmospheric pressure in the airlock. In this case it's 5.5 hours outside, but there will have been more time spent inside but in vacuum at the start checking the suits are working properly (especially after the water leak last time) and at the end making sure there's no ammonia been brought back inside.

I took a fish head to the movies and I didn't have to pay. -- Fish Heads, Saturday Night Live, 1977.