My Astro Photo Of The Day

[Autumnlicious]

A space elevator is indeed viable considering requirements for materials are met.

Check out the Mars Society conventions and websites for innovative ways to get to Mars, colonize or study it. It's famous and credible enough to have NASA and SpaceX present there.

One such idea involves harnessing an asteroid in a periodically adjusted elliptical orbit that intersets with Earth/Mars orbits to allow for gravitational assists. A benefit of that is that the asteroid, before it sling shots around the Earth, is in prime position of a highly elliptical orbit easily attainable from an Earth launched vehicle using funded and existing technology to rendezvous.

The challenge lies in orbital dynamics, patience (20 years to get the rock into full operational capacity).

The benefit of such is a body that can be mined for pre-existing volume, a free radiation shield negating the need for extremely dense materials required for throwing tiny ships of people at Mars, and can be used as an actual commitment to colonizing Earth's nearest neighbor for a rather cheap investment.

Remember that sending a few people to Mars ensures that colonization of it will be very delayed. With fewer people, less science can be done. And, if those people get cancer, they will lack the facilities that could be easily dumped en mass from a ship departing the asteroid before it slingshots around and the medical expertise and/or supplies.

All in all, looking at the past, sending a few explorers to the New World was suicide. Sending a fair bunch, though, is much more successful. And hopefully, unlike retarded puritans without planning, we can plan infinitely better.

Oh - yeah - this idea is mine. It's also been presented at the Mars Society, invited to 2010 COSPAR and is currently a continuing astrophysics project of mine at university.

[orogenicman]

Interesting idea. As for shielding, I had read somewhere that NASA was looking at the possibility of surrouding spacecraft with some sort of electrical/magnetic fields that would divert space radiation and cosmic rays away from habitation compartments.

[Anomalocaris]

A space elevator is indeed viable considering requirements for materials are met.

The space elevator concept has major dynamics problems. When you move a mass up a space elevator, the angular momentum of the elevator/mass combination is conserved, but the mass moment of inertia of the combination increases. Hence the entire combination must reduce its angular velocity to compensate. As a result, not only must the space elevator warp and deform as the mass moves up, creating complex dynamic problems, but the center of mass of whole structure will start to lag the earth's rotation. So the space elevator must not only continuously consume fuel to compensate for the angular momentum lost to the mass which it lifts into space, it must also consume fuel just to continuously maintain the correct tension and damp out the ocillations and pertubations in its own motion.

The solution to the material problem also by no means solves the dynamic stability problem during construction. 1, dropping a cable from a station in geosynchronous orbit into the surface of the earth simply does not work. The angular momentum of every part of the cable will be conserved during the descent, and the descending cable will lead the station in rotation, until the cable eventually wraps completely around the earth going in the direction of orbital rotation long before it reaches ground. 2. The same applies to any ascending cable intended to compensate for the weight of the descending cable. The ascending cable going up from the synchronous station will wrap itself around the earth going in the opposite direction of the orbital rotation.

I think the engineering challenges of lifting the necessary mass into geosynchronous orbit to start the construction, and to move the connections to and from the ground is so immense that the problem of material of adaquate strength pales in comparison. To say space elevator is viable because material strong enough is available is a little like saying flying buttress is viable as soon as reasonably sound stone is found.

Check out the Mars Society conventions and websites for innovative ways to get to Mars, colonize or study it. It's famous and credible enough to have NASA and SpaceX present there.

One such idea involves harnessing an asteroid in a periodically adjusted elliptical orbit that intersets with Earth/Mars orbits to allow for gravitational assists. A benefit of that is that the asteroid, before it sling shots around the Earth, is in prime position of a highly elliptical orbit easily attainable from an Earth launched vehicle using funded and existing technology to rendezvous.

The challenge lies in orbital dynamics, patience (20 years to get the rock into full operational capacity).

The benefit of such is a body that can be mined for pre-existing volume, a free radiation shield negating the need for extremely dense materials required for throwing tiny ships of people at Mars, and can be used as an actual commitment to colonizing Earth's nearest neighbor for a rather cheap investment.

Remember that sending a few people to Mars ensures that colonization of it will be very delayed. With fewer people, less science can be done. And, if those people get cancer, they will lack the facilities that could be easily dumped en mass from a ship departing the asteroid before it slingshots around and the medical expertise and/or supplies.

All in all, looking at the past, sending a few explorers to the New World was suicide. Sending a fair bunch, though, is much more successful. And hopefully, unlike retarded puritans without planning, we can plan infinitely better.

Oh - yeah - this idea is mine. It's also been presented at the Mars Society, invited to 2010 COSPAR and is currently a continuing astrophysics project of mine at university.

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.

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.

[Rhizomorph13]

Syn,

Are you talking about a Leyland whip maneuver?

http://wiki.uqm.stack.nl/Leyland_Gravity_Whip

I used to use those when I was piloting my Shofixti Scout to overtake those pesky Ur-Quan Dreadnoughts and unleash my divine wind!

For those that might not have heard or cared here is a link to download the full game of Star Control II

http://sc2.sourceforge.net/

[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.

---

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

---

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

[Rhizomorph13]

Yeah, Syn, because I was totally trying to blow everyone's mind with my comment.

[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?

[orogenicman]

NGC 281, The Pacman Nebula

I debated whether or not to post this one, since it needs a lot more data, and I had some instrument problems that night. But it doesn't look as bad as some I've posted, so I thought, why not?

From Wikipedia:

http://en.wikipedia.org/wiki/NGC_281

NGC 281 is an H II region in the constellation of Cassiopeia and part of the Perseus Spiral Arm. It includes the open cluster IC 1590, the multiple star HD 5005, and several Bok globules. Colloquially, NGC 281 is also known as the Pacman Nebula for its resemblance to the video game character.

Image:

5x5 minutes for a total of 25 minutes exposure at ISO 800
Stacked and dark subtracted in DeepSkyStacker
Proecessed in Abobe Photoshop CS3 Extended
Image taken on October 1, 2010 at Taylorsville Lake State Park, Kentucky

Equipment:

Hutech Canon T1i DSLR
200 mm f5 Konus Newtonian with a Baader coma corrector and a UV/IR cut filter
Losmandy G11 Gemini GOTO mount on Heavy Duty Tripod
Orion Shorty Autoguide Scope with Starshooter autoguider

[Tiberius]

NGC 281, The Pacman Nebula

I object!!! It looks nothing like Pac-Man!

[orogenicman]

Like I said, it needs more data.