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

by Vulch (#48424387) Attached to: What Would Have Happened If Philae Were Nuclear Powered?

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

by Vulch (#47875441) Attached to: SpaceX and Boeing Battle For US Manned Spaceflight Contracts

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:Decisions, Decisions... (Score 1) 123

by Vulch (#47873837) Attached to: SpaceX and Boeing Battle For US Manned Spaceflight Contracts

the first men on top will still be sitting on a rocket with far less launch history than the Falcon 9

I think you've got the history of the Atlas V wrong if you think it has less track record than the Falcon 9.

The CST-100 is sized to use the Atlas V, Delta IV or Falcon 9 as its launcher.

Comment: Re:GPS on Mars (Score 1) 104

by Vulch (#47405683) Attached to: ESA Shows Off Quadcopter Landing Concept For Mars Rovers

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

by Vulch (#45756483) Attached to: Smooth, 6.5 Hour Spacewalk To Fix ISS Ammonia Pump

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.

Comment: Re:Not-so-accurate source (Score 1) 487

by Vulch (#43922657) Attached to: BBC Clock Inaccurate - 100 Days To Fix?

No, "programmer hours" versus "staff days". As everyone who has worked in a large organisation, public or private, knows it is vitally important to have numerous committee meetings and consult all stakeholders to make sure all possible solutions have been investigated and a clear approach decided before any programmers get involved.

Comment: Re:Sorry, little retro rockets won't work for that (Score 4, Informative) 520

by Vulch (#43061587) Attached to: Neil deGrasse Tyson On How To Stop a Meteor Hitting the Earth
the momentum of the propellant from the rocket pushes against the asteroid, countering the thrust of the rocket

Only if you let it. The Gravity Tractor idea usually uses two ion engines aimed so the exhaust goes either side of the body being towed. The tractor stays in place and there's no unwanted momentum transfer.

Brain damage is all in your head. -- Karl Lehenbauer

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