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Traffic between orbits - VASIMR, Maglev...

Posted by: Ekkehard Augustin - Tue Aug 28, 2007 11:03 am
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Traffic between orbits - VASIMR, Maglev... 
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Post Traffic between orbits - VASIMR, Maglev...   Posted on: Tue Aug 28, 2007 11:03 am
I already had started a thread on this much earlier under quite another title and more limited compared to this.

The thought is how to enable spacecrafts to enter another orbit than it is in and perhaps to go back to the original orbit.

One of my earlier ideas were that a spacecraft might temporarily go to a (much) higher orbit where the required velocity is less and change inclination or shape of orbit there. Of course altitude would e changed already. May be that the altitude of the temporary orbit has to be extreme - the distance of the Moon or beyond.

Another earlier idea waere kinds of derivatives of space elevators which might catapult spacecrafts into other orbits than there original ones. These derivatives would be spinning parallely to the planetary surface or vertical to it either in parallely to the equator or verticaly to the equator.

Now in between orbital maglevs might be much more interesting because they could accelerate objects up to 27,500 km/h in relation to themselves - the velocity the maglevs themselves would be orbiting by.

But what about VASIMR applying for such traffic between orbits? Since AdAstra Rockets says that Isps of 10,000 seconds are possible it's looking to me as if the difference of that number to usual Isps of chemical rockets might enable vehciles to go from one orbit to any other obrit.

What about it?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)


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Post    Posted on: Tue Aug 28, 2007 3:16 pm
Using such a technology like VASIMR for changing Earth orbits is imo like using a truck to buy one bread.

The key element of that VASIMR concept is, as the name states (Variable Isp Magneto-Plasma Rocket), the possibility to change the specific impulse (my books say betweek 3000 and 30000s Isp typically) and therefore the thrust while operating on one power level.

Thrust ~ Power / Isp

A typical VASIMR engine will need a much larger power source contrary to the "normal" MPD engine in the magnitude of MWs (instead of kWs). So this engine is the typical application for nuclear reactors with its typical problems, mainly in the pseudo-eco-political sector.

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Post    Posted on: Fri Aug 31, 2007 10:59 am
Klaus Schmidt wrote:
Using such a technology like VASIMR for changing Earth orbits is imo like using a truck to buy one bread.

The key element of that VASIMR concept is, as the name states (Variable Isp Magneto-Plasma Rocket), the possibility to change the specific impulse (my books say betweek 3000 and 30000s Isp typically) and therefore the thrust while operating on one power level.

Thrust ~ Power / Isp

A typical VASIMR engine will need a much larger power source contrary to the "normal" MPD engine in the magnitude of MWs (instead of kWs). So this engine is the typical application for nuclear reactors with its typical problems, mainly in the pseudo-eco-political sector.


I would say maglev is a way in the future because of its mass. I still like the idea. I dont know much about VASMIR but Im sure it is a smaller project even if nuclear powered. Once we have a reliable way to move things around in orbit and never need to deorbit anything again, personally Im happy with the idea of heavy nuclear power up there.

I think I read a statistic that about 100 tonnes of space junk falls to earth every year?? Seems a waste after all the effort putting it up there.

Other possibilities could be
  • cheap fuel from the moon,
  • ..or scooped from earths's upper atmosphere,
  • charged particle beams from one central satelite.
  • Solar thermal propulsion
  • electrodynamic tethers


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Post    Posted on: Sat Sep 01, 2007 2:58 pm
Plasma rockets and Maglev technology are for two completely different applications. Plasma rockets like VASIMR are engines for interplanetary travel (direct flight paths) and capable of missions up to 100-1000 AU away.
Maglev technology on the other hand is for launching stuff into orbits.
Simply said, they can supplement each other.

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Post    Posted on: Sun Sep 02, 2007 1:59 pm
Klaus Schmidt wrote:
Plasma rockets and Maglev technology are for two completely different applications. Plasma rockets like VASIMR are engines for interplanetary travel (direct flight paths) and capable of missions up to 100-1000 AU away.
Maglev technology on the other hand is for launching stuff into orbits.
Simply said, they can supplement each other.


Ah, sorry, yes.

I expect VASIMR would be too slow for moving people between high and low orbits. I meant slow adjustments over months for unmanned satelites where the propellent cost is more important than the time. Here is a link that suggests it may be used first on the ISS for maintaining orbit, for example:

http://www.nasa.gov/vision/space/travel ... lsion.html


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Post    Posted on: Mon Sep 03, 2007 7:03 am
According to Ad Astra Rockets they in the short run seem to develop VASIMRs to keep satellites in their proper orbit - in so far VASIMRs are NOT focussed on Deep Space Travels and can be scaled so that they only can keep an object in a particular orbit.

Also according to Ad Astra Rockets a journy towards Mars applying a VASIMR would last 39 days instead of 150 to 180 which is far beyond keeping something in an orbit.

So it seems that VASIMRs are proper for lots of purposes and from this point of view I can't see no reason to NOT apply it for traffic between orbits.

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Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

EDIT: I in between did a raw calculation of the average velocity Ad Astra Rockets seem to apply for their 39 days to Mars and got a value of around 38 km/s.

I seem to remember that Phoenix is going by around 32 km/s. Both values include the orbital velocity of Earth of a bit more than 29,75 km/s. Regarding Phoenix this would mean that in total less than 3 km/s have been added by acceleration - so Phoenix's velocity inlcudes deceleration by Earth's gravity.

The 38 km/s are valid if Mars was in oppostion at farthest distance from the sun - so the value may be too high.

But my impression is that a VASIMR really might be an engine more proper for traffic between orbits than others. At present it might be the first one capable of such traffic at reasonable fuel consumption.


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Post    Posted on: Mon Sep 03, 2007 10:07 am
Ok, let's dig into numbers a bit (Sources Ad Astra and Felisa Y. Zhang from the University of Toronto):

Ad Astra's "low" power model needs about 10kWs of energy. This engine delivers a maximum thrust of 0.14N. For comparison the Soyuz spacecraft (not the rocket) has a main engine for orbital corrections and deorbiting of 3.1kN.

Plasma rockets require a high and high-density power source. And that is nuclear power. Bad enough that Project Prometheus was, like all its precursors, cancelled by NASA.

The achievable thrust for VASIMR is about 1-2kN with a high power source, that's then ideally suited for interplanetary (or if you will lunar) traffic.

For orbital corrections it seems doubtful that nuclear power will get a "green" *g* light from pseudo-ecologists.

Don't misunderstand me..I like the VASIMR concept but I see the problem that a private company (additionally one of Costa Rica) won't ever get access to a nuclear reactor.

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Post    Posted on: Mon Sep 03, 2007 10:32 am
Like already mentioned in a thread in the Financial Barriers section Ad Astra Rockets have published a drawing where the VASIMR seems to be powered by solar power. This drawing is linked to lunar or interplanetary trips if I remember correct.

This looks to me as if Ad Astra Rockets think they might get sufficient power for interplanetary trips by solar power.

In this thread here I don't consider the question if VASIMR might be used privately but really have in mind traffice between orbits only - regardless of this traffic being private or governmental.

I will have another look to Ad Astra Rockets' website.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

EDIT: The drawing applying solar power I found here: www.adastrarocket.com/PlasmaRockets.html


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Post    Posted on: Sat Dec 06, 2008 6:05 pm
I seem notto have thought about yet here - and marginally only elsewhere: Might tethers be capable of sending vehicles from an orbit of one inclination into an orbit of similar altitude and shape but another inclination?

They are seriously thought of for sendng vehicles into higher orbits or to the Moon - yes, but what about changing the orbit from equatorial to significantly non-equatorial?

What about catapults? I've read about serious thoughts to catapult vehicles to the Moon - so what about changing orbits that way?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)


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