My Astro Photo Of The Day

[Anomalocaris]

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.

When you are ready to land on the asteroid, you are matching the asteroid's orbit, which is an martian transfer orbit. So you've already burned all they fuel you would need to put yourself directly into your own mars transfer orbit even without an asteroid. Tada....

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.

I would hope the asteroid already has significant momentum. Everything else in the universe has significant momentum in relation to something. Momentum may be handy in calculating action and reaction, but its quantity is not exactly a very useful way to describe orbital motion. A combination of kenetic energy, potential energy, and direction of velocity vector is much more useful.

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.

Yes, the Rusty Schweickart - who talks to sagan - argument. That makes everything clear and plausible.

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.

A modified heliocentric elliptical orbit where at aphelion and perihelion the object passes out of solar sphere of influence into a local hyperbolic orbit under the sphere of influence of one of the planets is possible. But to keep this up like a tennis volley requires course planning so precise that extensive fuel burn would be required during each pass to ensure to the object pass through the correct window.

As to twice keplarian velocity, keplarian with respect to what? If to the planet it implies no gain. You need to exceed the Keplerian orbital velocity by at least a factor of 1.4 anyway just to leave planetary sphere of influence to go into a transfer orbit to where ever you are going. If it is with respect to the sun then I hate to tell you, but objects don't stay in orbit around the sun if travel at twice the average keplerian velocity. Escape velocity (from the solar system) is equal to 1.4 times the average keplarian velocity of a heliocentric elliptical orbit. Your asteroid will be visiting the Oort cloud, not Mars. Haven't gotten to that part of orbital mechanics yet, have you?

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

If you manage to make your ship match the orbit of the asteroid so as to be prepared to land on it, then you would have placed your ship under exact same gravitational influence that the asteroid would be under, and your ship would thus follow exactly the same path your asteroid would have followed, even if there was no asteroid. So your ship would coast to mars in exactly the same way your asteroid would have. Once you are there, your ship would sling shot around mars just like your asteroid. If you plan to depart from the theoretical orbit of your asteroid so as to land, well you have to burn the same fuel to so this either way. Orbital mechanics ring a bell? Along the way if your asteroid didn't need any fuel, neither would your ship if you place it into the same orbit as you would have placed your asteroid. If your ship needed some fuel to do course corrections, your asteroid would need a whole lot more. As to the weight of the ship's shielding, let's compare that to the fuel weight. Your ship only needs to carry fuel to make one set of orbital correction for a small ship to get into the Mars transfer orbit, and one set of correction to come out of Mars transfer orbit into either a martian orbit or a Mars aerobrake orbit. Your asteroid with its bonus shield would need to carry all the fuel for for orbital correction during each leg of its back and forth between mars and earth. One missed orbital window at either end of its elliptical orbit, and the thing slings off into the wild black yonder, needing another few dozen years to put back into correct orbit. Seeing the point? Mr. Sarcasm?