I'm doing a study into the intelligence of slashdot readers vs k5 readers for my Phd and I was wondering if you could all have a go at answering this question for me to help with my thesis conclusions
Imagine you have 2 waves, the sources of which are infinitely far apart. Now the 2 waves are 180o out of phase and so completely destructively interfere. My question is thus. Where does the energy go?
Has anyone tried running MythTv on one of the VIA Eden boards? I'm really tempted to build a media box but all the solutions I've seen so far are either too ugly/too noisy/too expensive. If the processor on one of these boards can cope with the video stuff then they would solve these problems at a stroke.
As a side issue do you know how the MythTv people are coming along with hardware encoding? The news on the site is a little confusing on that one.
What what whaaaaaat?!", you're saying? Nothing crazy about nuclear power on ships. Our nuclear submarines travel through an environment not unlike space
well its quite unlike space in that theres lots of water about. Let us think for a moment about why this might be important.
Submarines accelerate by changing the momentum of the water around them. They make a mass of water move backwards and then by Newton's third law the submarine accelarates forward. Simple.
Now in space there's no water, so you need to carry all the stuff you're going to change the momentum of around with you (usually hydrogen). I had a look at at the exhaust velocities of the nuclear thermal rocket engines and found out they were about 9000ms-1 (LOX / LH2 is about 4500ms-1).
If we estimate the weight of a mars casule at 15 tonnes (I just picked this figure out of thin air but some back of the envelope calculations on the weight of the nuclear reator came to about 10 tonnes so its on the small size if anything) then to get an acceleration of 1g we need an impulse of 15000*9.81=147150kgms-2.
Now as our nuclear engine can spew out hydrogen at 9000ms-1 we need 147150/9000 = 16.3kg of hydrogen to be pumped out every second. The total amount of fuel can then be worked out by 16.3*187836 = 3071118kg. This means that you need something like 3000 tonnes of hydrogen to power your 15 tonne capsule. Obviously the true figure would be much much higher because I haven't considered the impulse needed to accelerate the mass of the fuel.
Put simply the submarine engine isn't going to power a ship to mars in 50 hours.
The simple fact is that we're probably not going to get to Mars in the next 20 years, it simply isn't as simple as people would like to think. Most of the problems revolve around the fact that any expedition to mars would last up to 3 years(apollo 11 took around a week) and for the great majority of this the team would have to cope with problems unaided.
Consider this: The CLOSEST that mars gets to earth is 86.5 million KM which means that any communication with the earth is going to take 5 minutes to get there and the response 5 minutes to get back. That means that for any problem that can't be solved in 10 minutes you're completely on your own. The astronauts on Apollo 13 would have been doomed had they had a 10 minute communication lag with ground control.
other problems include sickness (its going to happen if you're away for months and illness that are trivial to cure on earth would be major problems halfway to mars, not to mention the degeneration of muscles, bones and the heart caused by being weightless for long periods of time), nutrition(how do we keep our astronauts in tip top shape for months on end when we have no way of getting food to them), radiation and pyschological problems (think being couped up in a space the size of your living room with 5 people for a couple of years).
Yes, most of these problems are solvable (especially if we develop a technology considerably faster than chemically fuelled rockets) but the fact is almost everything that a manned mission would achieve can be done for less money and risk by robots. Its just not going to happen.
Slashdot Mirror
I'm doing a study into the intelligence of slashdot readers vs k5 readers for my Phd and I was wondering if you could all have a go at answering this question for me to help with my thesis conclusions
Imagine you have 2 waves, the sources of which are infinitely far apart. Now the 2 waves are 180o out of phase and so completely destructively interfere. My question is thus. Where does the energy go?
Has anyone tried running MythTv on one of the VIA Eden boards? I'm really tempted to build a media box but all the solutions I've seen so far are either too ugly/too noisy/too expensive. If the processor on one of these boards can cope with the video stuff then they would solve these problems at a stroke. As a side issue do you know how the MythTv people are coming along with hardware encoding? The news on the site is a little confusing on that one.
What what whaaaaaat?!", you're saying? Nothing crazy about nuclear power on ships. Our nuclear submarines travel through an environment not unlike space
well its quite unlike space in that theres lots of water about. Let us think for a moment about why this might be important.
Submarines accelerate by changing the momentum of the water around them. They make a mass of water move backwards and then by Newton's third law the submarine accelarates forward. Simple.
Now in space there's no water, so you need to carry all the stuff you're going to change the momentum of around with you (usually hydrogen). I had a look at at the exhaust velocities of the nuclear thermal rocket engines and found out they were about 9000ms-1 (LOX / LH2 is about 4500ms-1).
If we estimate the weight of a mars casule at 15 tonnes (I just picked this figure out of thin air but some back of the envelope calculations on the weight of the nuclear reator came to about 10 tonnes so its on the small size if anything) then to get an acceleration of 1g we need an impulse of 15000*9.81=147150kgms-2.
Now as our nuclear engine can spew out hydrogen at 9000ms-1 we need 147150/9000 = 16.3kg of hydrogen to be pumped out every second. The total amount of fuel can then be worked out by 16.3*187836 = 3071118kg. This means that you need something like 3000 tonnes of hydrogen to power your 15 tonne capsule. Obviously the true figure would be much much higher because I haven't considered the impulse needed to accelerate the mass of the fuel.
Put simply the submarine engine isn't going to power a ship to mars in 50 hours.
The simple fact is that we're probably not going to get to Mars in the next 20 years, it simply isn't as simple as people would like to think. Most of the problems revolve around the fact that any expedition to mars would last up to 3 years(apollo 11 took around a week) and for the great majority of this the team would have to cope with problems unaided. Consider this: The CLOSEST that mars gets to earth is 86.5 million KM which means that any communication with the earth is going to take 5 minutes to get there and the response 5 minutes to get back. That means that for any problem that can't be solved in 10 minutes you're completely on your own. The astronauts on Apollo 13 would have been doomed had they had a 10 minute communication lag with ground control. other problems include sickness (its going to happen if you're away for months and illness that are trivial to cure on earth would be major problems halfway to mars, not to mention the degeneration of muscles, bones and the heart caused by being weightless for long periods of time), nutrition(how do we keep our astronauts in tip top shape for months on end when we have no way of getting food to them), radiation and pyschological problems (think being couped up in a space the size of your living room with 5 people for a couple of years). Yes, most of these problems are solvable (especially if we develop a technology considerably faster than chemically fuelled rockets) but the fact is almost everything that a manned mission would achieve can be done for less money and risk by robots. Its just not going to happen.
is winamp the most popular windows audio player? I'd be surprised if it wasn't Windows Media Player. Still your point is valid.