Author Topic: Vasimr: A true game changer? Role of Vasimir in future programs  (Read 74268 times)

Offline FinalFrontier

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So I am starting this thread to discuss the role of Vasimr in future programs, and in spaceflight in general.

Main idea:
Nuclear+solar vasimr for mars transport/deep space propulsion stage?

Other  potential uses:

Commercial applications
Deep space probe applications
EELV upper stage applications
National Security applications (?)

Open for discussion


The company
http://www.adastrarocket.com/aarc/

The planned engine(s):

3-30-2017: The start of a great future
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Offline FinalFrontier

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The second picture more resembles the general type of a potential future deep space propulsion stage combining both nuclear and solar power. Though it seems to me the only reason to fly it on a lunar mission, as opposed to a traditional JUS style EDS would be to test it out in prepartion for long duration deep space missions, to NEOs for example or elsewhere.
3-30-2017: The start of a great future
"Live Long and Prosper"

Offline A_M_Swallow

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VASIMR to the Moon uses less propellant than chemical rocket to the Moon.  This lower propellant means that the spacecraft can return to LEO to pick up more cargo.  The Argon propellant weighs less than the Earth Departure Stage and chemical propellant so the launch vehicle can lift more (final) payload.

One other use for the VASIMR (and its ion propulsion rivals) is station keeping for spacestations.  Soon there may be other spacestations as well as the ISS.

Offline aceshigh

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the ideal VASIMR ship would be powered by polywell fusion reactors... their lightweight and 100 MW of power for each would be the perfect match for VASIMR...

2 polywells (200 MW) and you get to Mars in 39 days... I wonder about the calculations for 4 Polywells (400MW)... how long to Mars or Jupiter...

Offline simonth

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1. Nuclear vasimr for mars transport/deep space propulsion stage?
2. Solar vasimr for mars transport/deep space propulsion stage?
3. Commercial applications
4. Deep space probe applications
5. EELV upper stage applications
6. National Security applications
1. no
2. yes
3. maybe
4. yes
5. no
6. no

And I agree, VASIMR (unless another tested technology comes along soon rivalling it in its application and efficiency) is a true game changer. Probably the ONLY game changer out there that can realistically be written into a BEO architecture.

As to nuclear power VASIMR MTVs... ain't going to happen. Yes, we like to talk about 200MW reactors in space, but there just isn't any money for the development and no political will at all to use them for actual missions any time soon. Especially when an alternative is available, that might even be a lot cheaper and less complicated (and which people fear less).

Offline butters

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We're going to need to get over our nuclear phobia in order to power a manned surface outpost on Mars.  I don't think solar would cut it on the surface, especially if we're going to the high latitudes where water ice is more likely to be found.

In my view, we have to do the robotic Mars sample return mission as a precursor to the manned mission, and for that, SEP makes the most sense, certainly between EML and LMO if not also direct from/to LEO.

From this technology base, it then makes sense to continue with the manned mission by sending the surface hardware and ascent vehicle to LMO via SEP.  Using hydrolox only for the manned orbital transport vehicle to and from LMO may not be so bad in terms of total mission IMLEO.

Then we can work toward an NEP (and/or NTP) solution for the MTV to improve the economics if and when that becomes possible.

Offline Robotbeat

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We're going to need to get over our nuclear phobia in order to power a manned surface outpost on Mars.  I don't think solar would cut it on the surface, especially if we're going to the high latitudes where water ice is more likely to be found.

In my view, we have to do the robotic Mars sample return mission as a precursor to the manned mission, and for that, SEP makes the most sense, certainly between EML and LMO if not also direct from/to LEO.

From this technology base, it then makes sense to continue with the manned mission by sending the surface hardware and ascent vehicle to LMO via SEP.  Using hydrolox only for the manned orbital transport vehicle to and from LMO may not be so bad in terms of total mission IMLEO.

Then we can work toward an NEP (and/or NTP) solution for the MTV to improve the economics if and when that becomes possible.
I agree nuclear is needed for the ground, though I'm not decided whether advanced "RTG"s or fission is better. Either would work, because power/weight isn't as much of an issue. You just need 10-20kW, any more is gravy (this is 1000th what you need for an MTV). Actually, I predict a mix of RTG and solar.
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Offline simonth

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We're going to need to get over our nuclear phobia in order to power a manned surface outpost on Mars.  I don't think solar would cut it on the surface, especially if we're going to the high latitudes where water ice is more likely to be found.

Solar on the Martian surface makes sense too, especially mass wise and for redundancy purposes. If your nuclear power reactor fails, the mission must abort, if one of 1000 solar arrays fails, nothing happens.


Offline kfsorensen

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VASIMR, if it to be considered fairly, needs to be considered in isolation from its power source, since any electric thruster can benefit from a low-mass power source.

VASIMR's performance coefficients, thruster alpha, and other parameters would need to be known so they could be compared to other electric thruster (gridded ion, Hall ion, MPD, pulsed-inductive, etc.)

Offline SpacexULA

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We're going to need to get over our nuclear phobia in order to power a manned surface outpost on Mars.  I don't think solar would cut it on the surface, especially if we're going to the high latitudes where water ice is more likely to be found.

Offers a great opportunity for international cooperation.  China and Russia would have no issues launching a reactor into orbit.  American VASIMR powered by a Russian/(not likely Chinese) power plant would make for a great international Mars mission.
No Bucks no Buck Rogers, but at least Flexible path gets you Twiki.

Offline kfsorensen

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"Nuclear phobia" or any other discussion of power source is immaterial as to whether or not VASIMR is a "game-changer".  Only the performance characteristics of the engine itself should be considered in this discussion, since power supply aspects can benefit any other electric thruster as well.

Think about VASIMR like a set of tires.  Don't think about it like the engine.  Is VASIMR a good set of tires or is another set of tires better?  Because with a hot-rod engine, any set of tires is going to look like high-performance.

Offline 93143

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the ideal VASIMR ship would be powered by polywell fusion reactors... their lightweight and 100 MW of power for each would be the perfect match for VASIMR...

2 polywells (200 MW) and you get to Mars in 39 days... I wonder about the calculations for 4 Polywells (400MW)... how long to Mars or Jupiter...

Polywells aren't inherently 100 MW, and actually the specific power of a 100 MW Polywell isn't very good...  You'd probably want well over a GW per core, possibly 5-6 GW, or 10 if you can get the magnets...

Also, since the power comes off at about 1.5 MV DC, VASIMR as designed isn't really the ideal engine.  It's probably better to use a relativistic electron beam to heat the plasma, or some such method that doesn't require a big heavy wodge of power conversion equipment that could weigh as much as the whole rest of the power plant...
« Last Edit: 06/15/2010 08:06 PM by 93143 »

Offline kfsorensen

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Does anyone know the "bb" and "dd" modeling coefficients for the VASIMR engine?  Those would be particularly useful in ascertaining the engine's value.

Offline 93143

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I believe VASIMR runs about 1 kg/kW (IIRC, at least for current models) and 60-65% electricity-to-jet-power.  Isp (which is variable, obviously) can go as high as 30,000 seconds with hydrogen, lower for heavier propellants.  You probably knew most of that...

Hopefully an engine designed to use a Polywell as a power source would be lighter, at least, if not more efficient too...
« Last Edit: 06/15/2010 08:17 PM by 93143 »

Offline kfsorensen

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The usefulness of the "bb" and "dd" coefficients is that they allow you to calculate the efficiency of the engine given a particular value of Isp.  Since ionization is a fixed penalty, all electric engines tend to have improved efficiencies at higher levels of Isp.  If engine efficiency was constant (which it never is), then the "bb" value would that number and "dd" would be zero.  But that's not the way real engines work.

Offline 93143

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I'm afraid I don't have that data.

Offline Solman

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VASIMR, if it to be considered fairly, needs to be considered in isolation from its power source, since any electric thruster can benefit from a low-mass power source.

VASIMR's performance coefficients, thruster alpha, and other parameters would need to be known so they could be compared to other electric thruster (gridded ion, Hall ion, MPD, pulsed-inductive, etc.)

 If you are only comparing electric propulsion systems and cost isn't an issue this is true. However if the comparison is with solar thermal/electric the fact that solar thermal does not require sunlight to be converted into electricity first, but rather can use it directly and thereby have lower mass( no conversion equipment required ) and higher efficiency. If electric propulsion is added to solar thermal, high efficiency high specific power concentrator type PV can be used to power it.

 Solar thermal has lower Isp, but can take advantage of the Oberth effect when going from low orbit to escape velocity to largely compensate for this vs. SEP and take a week or two as opposed to weeks or months with SEP. For Mars electric can then be used to speed things up, but need not have the kind of power levels that any all-electric needs to be useful. An all-electric has to have enough electricity to go from LEO to escape at fairly high Isp ( to compensate for its need to spiral out and the high mass of its power source ) and would need a source of electric power production far beyond anything reasonably available in the near future.
 VASIMIR's advantage is that it can operate at a large range of exhaust velocities. Solar thermal/electric may use two separate engines to do the same thing, but they both use the same large concentrator and solar thermal engines are low in mass for their thrust vs. electric. VASIMIR is more complex and heavier than MPD as well.

Sol

Offline A_M_Swallow

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VASIMR, if it to be considered fairly, needs to be considered in isolation from its power source, since any electric thruster can benefit from a low-mass power source.

VASIMR's performance coefficients, thruster alpha, and other parameters would need to be known so they could be compared to other electric thruster (gridded ion, Hall ion, MPD, pulsed-inductive, etc.)

 If you are only comparing electric propulsion systems and cost isn't an issue this is true. However if the comparison is with solar thermal/electric the fact that solar thermal does not require sunlight to be converted into electricity first, but rather can use it directly and thereby have lower mass( no conversion equipment required ) and higher efficiency. If electric propulsion is added to solar thermal, high efficiency high specific power concentrator type PV can be used to power it.

 Solar thermal has lower Isp, but can take advantage of the Oberth effect when going from low orbit to escape velocity to largely compensate for this vs. SEP and take a week or two as opposed to weeks or months with SEP. For Mars electric can then be used to speed things up, but need not have the kind of power levels that any all-electric needs to be useful. An all-electric has to have enough electricity to go from LEO to escape at fairly high Isp ( to compensate for its need to spiral out and the high mass of its power source ) and would need a source of electric power production far beyond anything reasonably available in the near future.
 VASIMIR's advantage is that it can operate at a large range of exhaust velocities. Solar thermal/electric may use two separate engines to do the same thing, but they both use the same large concentrator and solar thermal engines are low in mass for their thrust vs. electric. VASIMIR is more complex and heavier than MPD as well.

Sol

Solar thermal has one other major advantage - it can work in the Van Allen Radiation Belts.  IMHO There is a good living for a tug that goes between LEO and the Earth-Moon Lagrange points.

The electronics will need shielding but since computers are small that is possible.  The sensors may need replacing after each flight but that is a predictable cost.


edit: Add missing quote box.
« Last Edit: 06/16/2010 12:37 AM by A_M_Swallow »

Offline Namechange User

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Propulsion and power systems should not be isolated and treated as seperate entities when discussing "game-changing" technologies.  They really should be treated as an integrated system because one is going to require the other if we are truly serious about this.

Of course, this is not going to happen over night and the elimination of all else will not speed this up either. 
Enjoying viewing the forum a little better now by filtering certain users.

Offline GREverett

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Here is what I think SEP powered VASMIR looks like... Clearly a no
brainer for Lunar and NEO even Maned Venus flyby and/or Mercury
orbit... Mars is tough...

VASMIR
(The case for an intermediate manned mission to Venus space/Mercury using solar power)

Photovoltaic Data:

Boeing/Spectrolab: Solar cell efficiency of 41.6%  with concentrator, developed for the “FAST” program for space solar arrays.  (This may be increased by adapting metamaterials and altering the micro-geometry of chip surfaces, with a
50%  - 60% efficiency potential).

 

Current efficiency of Photovoltaic’ on the ISS = <> 12% without concentrators.
ISS has 2500 m2 solar array, delivers 110kw.
Photovoltaic efficiency (in space) is reduced by:
•   surface reflections from the protective coating on the array.
•   absorption of solar radiation and its conversion into heat. (This heat energy is subsequently lost by thermal (infrared) radiation into space).
•   internal heat produced by electrical resistance within the photosensitive semiconductor surfaces of the photovoltaic cell.
•   Surface contamination of the transparent upper surface (space dirt, dust, and scratches) which cause the illuminated surface to become less transparent.
•   Mechanical "aging" of the semi-conductor surfaces and electrical junctions of the photovoltaic devices due to their exposure to ionizing radiation and constant thermal fluctuations in the space environment.
•   Of course, solar arrays (panels) which are not aligned so that they intercept the incident light at right angles are reduced in their "effective area" and are also prone to increased surface reflection (due to the increased angle of incidence of the incoming sunlight). This causes a huge reduction in the overall efficiency of the solar array.
Soar Radiation Data:

Solar flux at 1 AU = <> 1,367 W/m², average.

Planet
Perihelion - Aphelion
distance (AU)
Solar radiation
maximum and minimum
(W/m²)
Mercury
0.3075 – 0.4667   14,446 – 6,272
Venus
0.7184 – 0.7282   2,647 – 2,576
Earth
0.9833 – 1.017   1,413 – 1,321
Mars
1.382 – 1.666   715 – 492
Jupiter
4.950 – 5.458   55.8 – 45.9
Saturn
9.048 – 10.12   16.7 – 13.4
Uranus
18.38 – 20.08   4.04 – 3.39
Neptune
29.77 – 30.44   1.54 – 1.47








 Solar array size necessary to deliver:

                                           110kw (ISS old cell tech.)  =   2,500.00  m² (constant size)
           1 Megawatt (lunar  tug with cells @ 50% eff.)  =   1,463.06 m² (constant size)
12 Megawatt (Venus/Mercury with cells @ 50% eff.) =  17,556.72 m² (size at 1 AU)
12 Megawatt (Venus/Mercury with cells @ 50% eff.) =  2,316.83 m² (size at Mercury)
         12 Megawatt (slow Mars with cells @ 50% eff.) = 48,780.49 m² (maximum size at mars Aphelion).

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