New Mars Forums

Why do people care so much about the personal lives of the royal family?  It seems unlikely that this marriage will have any noticeable affect on anyone here.

I have read a hypothesis that autoimmune diseases like asthma and some types of diabetes might be caused by excessive hygiene.  There seems to be some pretty good evidence supporting this idea, such as how the probability of these diseases occurring appears to be proportional to the people's standard of living.

The damage to the shuttle would probably be damage to the wings rather than to the life support.  Shuttle and ISS would still have trouble supporting a full crew for an extended period of time, but the situation should not be too critical if you only sent up around 4 astronauts on the shuttle rather than 7.  Later, when the ISS is more complete and better supplied, it will be capable of supporting more people.

If the dollar keeps getting weaker, then the US certainly should be able to compete in the international launch market.

I think that we can be fairly certain that the dramatic rise in atmospheric CO2 concentrations over the last 150 years is a direct result of human activities.  What is less certain is how much that increase in CO2 has affected the global climate.  Even less certain is how much it will affect the climate in the future.  We think that it is responsible for the slight warming trend that has been observed in recent years, but it is hard to get an exact quantification of it's effect, or an accurate estimate of what the future effects will be.

What else do you call a bunch of armed militants trying to overthrow the government?

There are also numerous court rulings that support that interpretation.  It also makes sense since the National Guard is the only well regulated militia that I know of which has an important role in national security.

The problem is that every time you give people better weapons to defend themselves, you are also giving other people better weapons to attack them with.  If you let people have whatever weapons they want, then you will end up with an arms race that the criminals will win.

Experience shows that larger rockets trump massed produced small rockets in terms of cost/lb to LEO.  This relative advantage grows if you want to go farther away from Earth than LEO.  Even if you ignore the difficulty in managing a flotilla of small craft and the failure modes added by having three separate refueling per mission, I don't see how the swarm of small vehicles could be more economical than a large vehicle.

It turns a solar sail into a sort of solar thermal rocket.  It could be useful, but I wonder what sort of Isp range it is expected to have.  If the Isp isn't high enough then the sail would not be worth using even if the microwave generator were free.

The geometric construction is equally trivial. 

MR, why do you think that we should limit ourselves to the mathematics and science used by the anchient greeks?  Much more powerful and usefull mathematical tecniques have been developed since then.  It makes no sense to only use outdated ideas and methods when we now have something that is clearly better.

Newtonian physics is classical physics.  Modern physics is based on people like Einstein, Plank, Heisenberg, Schrodinger, etc.

The power it takes to accelerate the fuel is equal to the mass flow rate times the square of the exhaust velocity(P=mC^2).  In other words, power equals thrust times exhaust velocity(P=TC).  This is a basic result of kinematics and applies to all types of engines, not just VASIMR.  All electric engines are basically power-limited, so you have to make a trade off between thrust and Isp.

There is a lot of hype around VASIMR, but it helps to remember that it is just another electric engine, and that it is bound by the same restrictions that apply to other electric engines.  According to its proponents, VASIMR will be thottleable through a wider range of Isp than current electric engines and have a higher power density.  It will also not have any problems will grids wearing out and having to be replaced.  However, as nice as these advantages are, they are all evolutionary rather than revolutionary.  Modern ion engines are already at least 60% efficient, and they typically weigh less than 20% as much as the power plants that they need to run them.  Since electric engines have already gotten this advanced, much more improvement can be gained through work on power plants than on the electric engines themselves.

Definitely true.  Even a nuclear thermal engine has difficulty getting off the ground on Earth, and nuclear thermal engines can have a much higher specific power than any nuclear electric engine due to the lack of things like radiators and turbines.

Current/near term power plants would be able to operate a VASIMR in space without any problems.  Just don’t expect it to get you to Mars in a month or anything like that.

No, he hasn't.

No, it hasn't.

People can't change the laws of physics.

There are also a lot of science fiction ideas that have proved to impossible or impractical.

Cold fusion is still a myth.

Openness to new ideas can be a good trait, but blind faith in ideas that have little/no evidence to support them is usually counterproductive.

I think that people who say they know how to create a vehicle that can exceed the speed of light are a lot more like "flat Earth" people then people who don't claim to know any way to violate relativity.