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Object hopping...

Posted by: Ekkehard Augustin - Sat Aug 13, 2005 8:20 am
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Object hopping... 
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Post    Posted on: Fri Oct 27, 2006 7:11 am
Hello, WannabeSpaceCadet,

I am thinking into such things more and more detailed in most cases - I am doing it at this board since I registered in June 2003.

And so I already have the idea of the tethers - in principle the thought about space elevators are behind the idea of the web or net. And even the tether competition at the XPRIZE Cup seems to be of meaning for this.

It will not be possible to forget about the asteroids because there is the idea to make use of them as shields against space radiation and somehow a vehicle must get onto or into the asteroid.

That you mentione the difference in velocity is puzzling me - I myself mentioned it. I did not say that the difference shuld not be appreciable but only that it must not be too large and not too small. This is one of the points that brought the idea of the webs and nets to my mind. If the web or net touches down onto the asteroid instead of the vehicle itself then at firstv this could reduce the effect on the vehicle. The web simply wuld have to be long and still rolled on to a significant degree. Then it could be rolled off at touch down to reduce the effect on the vehicle to a degree where the effect isn't dangerous no more. The vehicle will be accelerated too but a bit less than the web at touch down. Then the vehicle could move along the web by electromotors driven by solar power.

Another way might be to apply shock absorbers at touch down.

Up to now I haven't been speaking about numbers - in so far it is not clear about what concrete velocities and differences between them we are talking.

Also I would prefer experiments over theoretical couter-arguments. Such experiments in principle are easy to do. There are sufficient objects in LEO that are dead and that could be used to experiment with controlled approaches by experimental vehicles - experimenting touch-downs of vehicle onto an object with the vehicle flying in front at less velocity when the object is close, using a web and more.



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Post    Posted on: Sun Nov 05, 2006 3:46 pm
Of course the question is how larger the shock absorbers had to be.

But it might be a solution if the vehicle wouldn't fly directly in front of the asteroid but somewhere between that direction and 90° to it.

Even in the case of using the asteroid as a shield against radiation something is required that protects the vehicle from damages by contacts to the asteroid - in so far it may be that the vehicle simply doesn't touch down but is getting surrounded by the faster asteroid and then its velocity is adjusted to that of the asteroid. ...

...

Another point I am still thinking about is the use of asteroids that cross the orbit of Earth. As such asteroids move away from the sun they are decelerated but still might be faster than the vehicle when they are at the distance of Earth.



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Post    Posted on: Wed Jun 27, 2007 1:19 pm
Because of two recent articles under www.space.com I have become aware that DAWN in principle might be a prototype of an object-hopping vehicle.

If ISRU would be devloped already and if it would have got to a certain degree and stage of evolution and development I in principle would have preferred a quite similar mission entering an orbit around Ceres first to refuel LH2 and LOX there from the water ice of Ceres. This mission would visit Vesta second.

But I would extend this mission to go for at least one next planet having huge ressources of water. And so on.



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Post    Posted on: Wed Jun 27, 2007 8:20 pm
Please believe the other posters that there is no advantage to running into an asteroid unless you can harpoon it with a bungee cord. The relative velocities necessary to make it worth while are simply too large to do anything mechanical.


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Post    Posted on: Thu Jun 28, 2007 6:45 am
Hello, DanielW,

my post yesterday didn't have nothing to do with running into an asteroid but simply and only with using them as well as moons and planets to refuel there to be able to fly to the next outer one without the requirment to carry all the fuel from Earth.

Regarding the posts you might be referring to I simply was - and still am - thinking about something and one of the thoughts posted is similar to "harpoon it with a bungee cord".

There also is the circumstance that a few posters tend to consider things within the capabilities of now, today in 2007 while I allways have in mind that capabilities tend to be extended, improved, increased and the like. I have no problem if something takes decades or centuries until it is possible or until the capabilities are available - the present impossibility or/and unavailability of capabilities simply means that it
can't be done yet now but the requirements etc. can be explored to find out which capabilities and possibilities are required. Please remember Harperns work about artificial and passable black holes - he explores the requirements of the construction of such black holes but the construction is quite impossible at present and none of the capabilities is available at present. Harpern simply is talking about something that might be possible in a very far future perhaps.

To land on an asteroid at least might offer the opportunity to save fuel, propellant even for course corrections.

But in my previous post the focus is on hopping from planet to planet or moon for refuelling via ISRU.



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Post    Posted on: Fri Dec 07, 2007 11:53 am
The article "'Flying Saucers' Around Saturn Explained" ( www.space.com/scienceastronomy/071206-saturn-moons.html ) is a reason to me to extend the scope of this thread and topic a bit.

In this thread I also posted because of a student's idea and concept to fly a vehicle into an asteroid that is a conglomerate of stones and dust merely than a solid rock to get better and improved protection against radiation.

This application of an object I feel reminded to by the article linked to in combination with Peter Kokh's idea to arm a manned vehicle by a water ice to protect the crew against the radiation in the jovian radiation belt when landing manned on the jovian Moon Europa.

Peter Kokh's idea is to land on Kalypso which still is outside the jovian radiation belt and to arm the vehicle there.

But the article linked to causes me the idea to unmanned and remotely or automatically/robotically fly a vehcile into the saturnian rings that is capable of attracting particles of the rings that might be very rich of ice. The vehicle also might grab larger particles and place it into a jacket.

This is similar to fly it into a conglomerate-like asteroid and would avoid landings on ice-rich planets. When armed by water ice up to an amount aimed at the vehicle might leave the rings and return into the inner solar system.

But it will have to be kept sufficiently far away from the sun to keep the ice I think. So it might be parked in any martian orbit or in any jovian orbit far outside the jovian radiation belt.

...
...
...





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Post    Posted on: Fri Jul 04, 2008 6:20 pm
Under the aspect of hopping from object to object to refuel there and thus save the weight of fuel to be brought from Earth as well as tank weight a news under www.welt.de sounds interesting.

The article tells that scientists have found that an additional planet in the Kuiper Belt may well explain the stability of the orbits of the objects there - some of them don't react to the Gravity of Neptune.

The hypothetical planet that could explain the stability would have to have half the mass of Earth and it would be 100 to 200 AU awy from the sun. 100 AU from the sun perhaps wouldn't be that interesting since Eris is 97 Au away - but the direction might be more interesting if it is pointing more to Alpha Centauri than Eris' direction. Regarding fuel and refuelling a distance around 150 AU would sound more interesting to me.

The orbit of that planet would have an inclination of up to 40° which would explain why it hasn't been discovered yet.

To some degree the article sounds as if the planet might be a gas giant althought nothing like this is said.

The article refers to Patryk Sofia Lykawka of Kobe-University in Japan



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Post    Posted on: Thu Aug 21, 2008 3:34 pm
Because of the article "Huge Comet Discovered" ( www.space.com/scienceastronomy/080818-new-comet.html ) I am thinking a bit about object hopping beyond planets of plutonian size or dwarf planet-size.

According to the article
Quote:
its elongated trek takes it to a distance of 150 billion miles (241 billion km)
and
Quote:
Its diameter is estimated at 30 to 60 miles (50 to 100 km)
.

So it might be interesting to do one hop to that object.

www.wissenschaft.de is reporting about it also and says that the major semiaxis is four times as long as the minor semiaxis.

Under this aspect the object seems to be not that interesting for a hop to refuel a vehicle - but it seems to provide a theoretical refuelling stop short beyond Neptune and a long way before Pluto.

It will be interesting when the object will be farther away than Pluto and by an interesting distance.

But to do the required stop its gravity will be of no help - the vehicle would have to slow down and stop of its own. This means that the object will be comfortable for refuelling only if the amount of propellant consumed can be kept significanly below the amount that can be refuelled at the object.

Interesting might be distances allowing for deceleration at a small rate or short enough to have not gained high velocities. At short distances the object is interesting if the tanks couldn't be refuelled entirely at the earlier stop.

But I didn't consider yet the amount of fuel to be consumed for refuelling at the gas giants.



What about it?

There also is the thought of hopping from Oort Cloud-object to Oort Cloud-object if there aren't Pluto-sized planets (and larger) in the right direction.



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