Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?
Last Chance - Get 15% off sitewide on Slashdot Deals with coupon code "BLACKFRIDAY" (some exclusions apply)". ×

Comment Re:Logical Consequences (Score 1) 398

there's a big difference between having nukes, and using them. MAD.

nukes are not only a response to nuclear aggression (which has not happened), but they are also a STRONG deterrent against conventional aggression - because the aggressor has to be very willing to accept escalation. no one wants that, unless they are insane (N. Korea.. looking at you).

Comment Re:Logical Consequences (Score 2) 398

or perhaps they would not have invaded at all, given a potential nuclear response.

it's easy to tell other nations that they should not have nukes, sitting in a nice safe position of having lots of them. no one wants nuclear proliferation, it's a very slippery slope - but from the point of view of nations who are being stamped on, would you trust the US to come to your aid, especially given how well it worked out for Ukraine?

Comment Re:Logical Consequences (Score 3, Insightful) 398

they were put under a 'nuclear umbrella' - but only in response to nuclear threats. and since Russia has not used nuclear weapons, the US, UK etc are free to 'ignore' the problem. Ukrainians are understandably upset that they gave up their nukes.

see how Japan might interpret this action? what if China does something that upsets Japan? will the US get involved, or come up with reasons to ignore the problem? would China be much more careful around Japan if they were nuclear armed? I think so..

Comment Re:Logical Consequences (Score 5, Insightful) 398

Yeah, this seems a bit silly.

Japan is already protected by the US nuclear program, so nothing really changes.

so was the Ukraine, in exchange for giving up their ex-Soviet nukes. see how well that worked out for them?

when push comes to shove, the US may, or may not, honor its commitments. it all depends on how much they want to go to war with China.

Comment Re:Russian Engine (Score 4, Informative) 176

I could be wrong on this, but I thought Pratt was going to be building the RD Amross (which is the american version of the RD-180) starting a couple of years ago. If that's the case then the RD-180's being used on the Atlas V are completely domestic.

no. they spent a small fortune on 'investigating the possibility' of building the engines in the US, which culminated in building one small part of an engine. then concluded that it was too expensive (a billion dollars to start production, and the US engines would also be twice the price).

RD-180s are built in Russia. they have a two year stockpile here in the US.. but ULA have just been awarded a five year block buy.

Comment Re:Thrust vector control (Score 2) 127

there is only a single nozzle on the grasshopper - one merlin 1D engine. the second, angled off to the side, jet of flame that you see is the low pressure exhaust from the gas generator on that engine, which has then ignited on contact with the oxygen in the air, since it runs fuel rich.

it provides very little in the way of thrust, and is not controllable on the 1D. on the merlin 1C vacuum version, it was directed and used for roll control - it appears that the merlin 1D-VAC directs the turbopump exhaust into the main engine bell to improve ISP, so presumably they plan on using cold gas or draco thrusters for upper stage roll control now.

you're correct that merlin 1D (and all the previous merlin models) use high pressure fuel from the output of the turbopump as the hydraulic fluid for gimbaling the engines - which has the nice advantage of not being able to run out of hydraulic fluid (or at least: you only run out when the engine quits firing).

Comment Re:Have you actually driven a Model S? I have (Score 1) 452

'based on a Lotus Elise' would be the Tesla *Roadster* - which they haven't produced for a couple of years now. the car everyone is talking about in this story is the Model S, which is built from the ground up by Tesla as a pure electric vehicle, and is therefore a much more optimal solution.

'42% US power came from coal in 2011' - and it's dropping rapidly in most states (ie the non-coal producing ones). some states are 0% coal. doesn't matter either way. even at 42% coal, the power station is still far more efficient than an internal combustion engine (ICE is 20-25% efficient, coal power station is 80+%). that's where the official government MPG values come from - 92 MPG equivalent (based on CO2 emissions). reduce the coal percentage in your state and that MPG value climbs dramatically.

Comment Re:locking? (Score 2) 372

postgres uses MVCC, similar to oracle.

oracle uses an undo log and postgres a redo - the difference being that oracle is faster for multiple updates (and may be quicker to restart after a crash), but postgres doesn't suffer from running out of log space with large transactions, and rollback is very quick.

both postgres and oracle perform far better under locking scenarios than sqlserver.

recent postgres also have some very smart stuff if you use serializable isolation mode; supposed to be better than any other DB.

Comment Re:Interesting fact (Score 1) 85

no. what they did is take the 40 year old engines and refurbish them (replace perishable seals etc), then add modern, western electronics and gimbal hardware and adjust for RP-1 rocket fuel rather than the 1970's Soviet equivalent.

whether they could actually produce new engines under the license they have is an open question - there has been a license for the RD-180 (used on the Atlas-V) for a long time, but no attempt at production has ever been made in the US. hell, they may not even be able to make new NK-33s in Russia, let alone the US - they were ordered to be scrapped and all the documentation destroyed - it was only due to a forward thinking (and brave) bureaucrat that they were warehoused and forgotten for 30 years...

these old Soviet design engines have very complex, tricky to reproduce metallurgy; that's why they are such good engines. but whether the formulas for that still exist.. who knows? they can certainly make new RD-180s in Russia, maybe the NK-33s use the same stuff, maybe not.

Comment Re:pop (Score 2) 111

no, that comes later, just before MECO, and it's not to reduce dynamic pressure, it's to keep the G-forces on the payload from getting too high as the rocket loses weight (by burning fuel/oxidizer) and accelerates faster. the new F9 1.1 (yet to fly) has engine throttling capability and is supposed to throttle down around Max-Q (F9 v1 can't do that, no throttle capability) and before MECO, instead of shutting down engines.

this was definitely an unexpected problem with either the engine or the fairing around it.

that said, the rocket coped amazingly well given the spectacular loss of an engine... adjusted and compensated in real time and ended up dropping Dragon off within 2km of the target.

Comment Re:Will they have to use The Arm in the future? (Score 1) 217

the 'failed Soyuz docking attempts' (there was only one) was a result of the cash strapped Russians trying to dock *without* the automated systems (actually - they were turned off, as a test, to see if they could save money in future by not having them).

docking is easier because (a) the vehicle approaches along the V-bar and (b) the vehicle is aiming to contact a target, with some tolerance.

berthing requires (for the ISS) approaching from the R-bar, which is much harder, and also must rendezvous with a precise point in free space, ready to be grappled. it also requires a skilled robot arm operator, and doesn't allow the vehicle to be used for crew, because it cannot unberth itself without robot arm assistance.

Radioactive cats have 18 half-lives.