My Astro Photo Of The Day

[Autumnlicious]

I am confused.

To launch a spacecraft from earth and to have it dock with an asteriod in a mars transfer orbit is the same as to launch that spacecraft independently into mars transfer orbit. So using an asteroid is no gain in attaining mars transfer orbit from earth.

To make course adjustments while in a mars transfer orbit while docked with an aseroid means moving the whole asteroid, while to make course adjustment with independent spacecraft in mars transfer orbit means moving just the space craft, so using an asteroid here is a real loser.

Incorrect.

First off, the asteroids orbit intersects with just inside Earths and Mars orbits. To get to it before it gets a gravitational assist (valid term of art), one must merely launch into a highly elliptical orbit, obviously increasing eccentricity over time, until one attains a velocity that would coincide with making landing on the asteroid.

Next, you're utterly disregarding the fact the asteroid already has significant momentum, and is adjusted over a significant period of time with successive interactions with other celestial objects. In addition, the proposed orbit (desired and resulting) must be considered in half orbits, while the difference between the phases follows a periodic function. Thus one must adjust the orbit occaisonally, most likely using the same thrusters that perturbed the orbit in the first place. Proposed thrusters use B612 foundations ion thrusters, which are proposed to be used to facilitate NEO deflection. Side note: Person heading this foundation (B612) (who frequently got into arguments with Sagan) is astronaut Rusty Schweickart.

When the asteroid does a flyby Mars, and thus a gravitational assist (calculated so as to allow the next half orbit), spacecraft merely need to disengage and aerobrake.

The majority of energy in this system to adjust the orbit comes from the planets, like two people playing catch. Another piece of the proposed enforced resonant bi-elliptic orbit is that it moves at twice the normal keplerian speed of an object.

To undock a spacecraft from an asteroid in a mars transfer orbit and put it into an orbit around mars is the same as sending spacecraft in independent mars trasnfer orbit into orbit around mars. So using an aseroid here is also no gain.

The the net effect seems to be use an asteroid to travel to mars is a net loser.

Except that the asteroid already has a defined volume, provides a surface for radiation absorption, and is powered by gravitational interactions. Sure, the spacecraft will be in orbit around Mars, just like as if it had been launched from Earth - excepting the annoying fact of the time, shielding (takes a lot of mass) and energy to get there.

So no, it isn't a "net loser".

In terms of sending light orbiters to rendezvous with a slingshotting near earth asteroid compared to sending small, heavily armored ships that must carry significant quantities of fuel? Definitely a loser.
/sarcasm

But I suppose we can always try going for the silly idea of generating a massive magnetic field, ignoring the power requirements for generating a significant deflection field. Or some moronic notion that we must send massive ships on ridiculous voyages. Or some pipe dream altogether, instead of something that uses current and developing technology.

Oh well.

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Side comment - this isn't the first time I've had to crack the Little Book of Orbital Dynamics on other people's heads.

Oh, Rhizo, that game reference is rather stupid.

For the science involved behind that rather annoying reference, here:
http://en.wikipedia.org/wiki/Gravity_assist

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Edit from later: Sorry for being a bit snappish - I'm a bit worn from today.