Posts by Vulch

Re: Ok what have I missed

Simples. You've used two different time units. 8600 km per *hour* and 9.82 m per *second*^2. You did the multiplying by 1000 to change the km to m, but skipped the 3600 to change seconds to hours or vice versa.

Re: Can some boffin explain how it works

It's a combination of light pressure and solar wind acting on the various stuff evaporating from the comet. The small gas and dust particles are affected more than the main body of the comet so start lagging behind.

When a comet picks up a large sideways component to its velocity you quite often get multiple tails as different size gas molecules and dust particles are sorted by the acceleration they pick up from the light.

Re: Amazing!

One advantage of hypergolic fuels is that they self ignite as soon as they mix so you don't get much of an explosion. The American Titan II used the same sort of fuel which led to the Gemini launch escape system being ejector seats instead of the solid rockets used on Mercury and Apollo.

Re: There are other issues

"the concern as to whether the pad would survive holding down an SRB for two minutes"

Ooh! An easy one! It wouldn't. Once the SRB lit it was going somewhere, the question was how much else of the stack went with it. If both lit at the same time then everything was fine, if only one lit then the external tank was going to rip in half. The hold down bolts were triggered by the same signal that fired the SRBs anyway.

There were a couple of cases where the explosive nuts on hold down bolts failed to fire. Either the bolt would stretch and snap (it was actually designed to do that) or the whole thing would pull through the skirt of the SRB.

Re: If you're going into deep space you'll be using nuclear power

Voyager type RTGs won't do the job. At launch they only produce 470W from three units massing about 38kg each. Back of an envelope gives about 250kg for 1kW so a couple of tonnes to get the 8kW needed. A Russian TOPAZ gets closer, 300-1000kg for 5kW but at the low end there's no (or very minimal) shielding so you'd not want to put it on a long duration flight.

The cut-over between solar and nuclear power for payload operations is generally the asteroid belt, although the Juno mission currently on its way to Jupiter is solar powered due in part to there not being enough of the relevant Plutonium isotope to build the RTGs needed. The Curiosity rover had first call on it and even then there wasn't quite enough and a couple of instruments got dropped. There's a second Curiosity type rover due to go to Mars in a few years time, it looks like that will have to use solar panels as Spirit and Opportunity did.

Re: Low earth orbit question ....

Makes the antenna tracking more difficult. For an equatorial orbit the satellites will only ever move along a single line across the sky, for an inclined orbit not only will that line appear to move as the earth rotates underneath it but the ground station will also need to switch to the next plane of satellites as the line vanishes below the horizon.

Re: Wibbly wobbly pebbles!

No, it's not raining...

I think you imagine wrong. Number plates fall under the Construction and Use Regulations which apply to vehicles on land customarily used by the public, car parks included, as well as on the public highway.

Re: I want to . . .

Bring back Motorail. Drive your electric car to the station and on to the train, plug it in to the wagon which is tapping a bit extra from the overhead, drive your electric car off again at the other end with a nice recharge.

Your robot self driving electric car could even drop you off by the ticket office, park itself on the wagon and hook up to the charger and be waiting outside the exit at the far end...

Re: 1 MW Electric - What about the Batterys

You'll probably need to run the main engine for a few minutes to charge the lift-off/landing batteries before you go. Two electric motors and some batteries are likely to be lighter to carry round when they're not needed than two IC engines capable of lifting the thing. It's like Formula 1 KERS for aircraft.

Re: American jobs

Alenia made the Columbus lab, most of the nodes, the three MPLMs and now the pressurised cargo section of the ATVs. They came up with a kit of parts with plain ring, ring with 4 CBM ports, plain endcap, endcap with CBM and endcap with Russian docking port. Pick two endcaps and however many rings you need and there's your module.

Re: Fuels

There was actually a problem with tankers for V2s turning up with less fuel on board than they'd started out with.

The percentage of water was down to ease of manufacture and handling in the engine, the fuel was used for cooling the engine chamber before being burned and getting 75% abv probably only needed a single distillation. The V2 did use peroxide, but for driving pumps, not for propulsion.

Re: Commercial power generation potential?

Usable power for power generation is a very different thing to usable power for propulsion. I would expect this engine to actually produce more energy than was used to trigger it, but it won't be in a form that can be siphoned off to trigger the next bang.

Re: Range?

For this sort of thing the drone will almost certainly have an auto-pilot (eg ArduCopter) that will let it follow a pre-programmed course. It's more likely to be the limited flight time (10-15 minutes) of a hexacopter will restrict them. There's a reason that entrants to http://www.theregister.co.uk/2012/10/07/uav_challenge_canberra_win/ tend to have fixed wings instead of rotary.

Re: With a little help from my friends (FTFY)

Launch costs can be difficult to determine. Russia markets the Proton to the West through a US company, International Launch Services, who tend to quote prices a bit under those of Ariane and Atlas 5/Delta 5 launches. There's good reason to believe that a Proton is built by around 50 people in a bit under a year, putting the basic unit cost at around 10 million. The Soviet Union put in a lot of effort up front at reducing the manufacturing costs of its launchers and making them easy to check out prior to launch, Soyuz and Proton were both designed as ICBMs so the plan was to have lots of them and to be able to launch them at short notice. SpaceX have learned those lessons and should be able to reduce their costs as the Falcon designs settle down.

Re: It's all very well giving the location

Given the location you're unlikely to be far out if you assume sea-level and go for an airburst at a couple of hundred feet.

Re: How about a "BIGGER HAMMER" variant of flaming

Will there be enough oxygen around at altitude for the magnesium to catch though?

Re: Technical Matter

Salvage doesn't apply to any government vehicle.

Re: Classic Yanklish

Surprised there's no mention of driving on the left

Not a problem in Station Road, there's the station car park if you can beat the commuters or increasingly distant short term car parks. They'll be walking the last mile anyway.

Re: No Laws Broken?

If Australian law matches English in this respect, bets are "debts of honour". There's no legal recourse for failure to pay out or against cheating.

Re: So far...

The liquid oxygen tank is at the top though so the weight distribution is vaguely dumb-bell shape.

It's actually easier to steer a rocket using vectored thrust if the weight is high up, if you've got a Fred Astaire style dancing cane, or failing that a small hammer, handy try balancing it on a finger both ways up and see which is easier to control.

Re: You are having a bad day and will not go to space today

"shareholders' confidence"

SpaceX is a private company, what few shareholders it has probably have Elon on speed-dial.

Re: A modest proposal...

As ever, the limits are money and time. It needs big telescopes, you're trying to spot black double decker buses several million miles away, looking in all directions all of the time. Ideally you want them spread around Earths orbit round the sun as well as on the planet itself, and also in Venus' solar orbit so they can look out towards us. Then you need enough computer power to analyse the stream of images from the telescopes and look for anything moving, and correlate between telescopes when they do spot something to determine its exact position and orbit.

Re: Falcon Heavy will freeze in deepspace...

Would you care to explain "Augmented by hydrazine"?

Curiosity separated from the Centaur less than an hour after launch, there was no reason to try and store fuel for use later. And if your claims of the temperatures expected had any basis in fact, why would hydrazine be any use? It's got a freezing point of 2C.