Re: Space Policy: Why Mars should be our top priority.

On Sat, 25 Apr 2009 04:01:05 -0700, Fred J. McCall wrote:

Marvin the Martian <marvin@xxxxxxxxxxxx> wrote:

:On Fri, 24 Apr 2009 19:14:47 -0700, Fred J. McCall wrote: :
:> Marvin the Martian <marvin@xxxxxxxxxxxx> wrote: : :> :Energy wise &
rocket wise, Mars is closer than the moon, : :>
:> You've said this before. I've pointed out that the source you gave
:> doesn't agree with your claim. Go add it up for yourself. :
:Yes, I've said it before.
:
:You didn't point out anything.
:

Yeah, I did. Let me point it out again.

:
:Let's go here:
:http://en.wikipedia.org/wiki/Delta-v#Delta-vs_around_the_Solar_System
:From LEO to the moon surface is 4.1 km/s + 1.6 km/s. :
:So the KE from LEO (Low Earth Orbit) to the moon is 1/2 m v^2 = 16.24
kJ/ :kg.
:
:From LEO to Mars is 2.5 + 0.7 + 0.6 = 3.8 km/s The red arrows indicate
:the opportunity to Aerobrake; using the planet's atmosphere to slow
down :rather than needing rocket energy. So the KE from LEO to Mars is
7.22 kJ/ :kg, less than half the energy of the trip to the moon. :

You're reading it wrong. Let me point out an example of what the way
you're reading it implies. Look at "Lunar Orbit". If your reading is
correct, one can assume one can get from lunar orbit down to Earth's
surface purely on aerobraking.

Of course you can't do that. Neither can you disregard the entire
velocity change required from Mars Transfer to Mars Surface by claiming
you can do it all by aerobraking.

:
:What I said is true, and what you said... yeah. right. :

What you said is poppy***. But then we just need to consider the
source.

The "fallacy fallacy" followed by your immature childish argumentum ad
hominem.

The red arrows do indicate an opportunity to aerobrake. In most cases,
the amount of delta V needed in the aerobrake sections is trivial. You
found the one case where the delta V is not trivial, and then threw out
the entire chart. This is known as "The fallacy fallacy". None of my
argument included the route in question. To go back to Earth from LLO is
more like a delta V of 4 km/s

My argument, of course, stands. You don't even try to refute it in any
rational way (an alternative delta V calculation being the only rational
way).

People should know that energy wise, Mars is closer than the moon.

Look at how BIG the rocket is to get to Low Earth Orbit. Now look at how
big the re-entry vehicle is; they're tiny in the case of the Gemini
program. You would think that the same size rocket would be needed to
change the delta v back to zero relative to the earth surface; but
instead, we can take advantage of the atmosphere to slow down.

Since Mars has an atmosphere, and the moon doesn't, this accounts for
much of the lower delta V going to Mars.



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