Author Topic: VASIMR Engine  (Read 123309 times)

Offline Alf Fass

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Re: VASIMR Engine
« Reply #60 on: 12/14/2014 12:20 AM »
The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

I suppose you could abandon the VASIMR its solar panels, and aerocapture the rest of the craft.

Seems a bit of a waste.

Wouldn't retractable panels solve this problem?  Given the surface area needed for something like VASIMR you have to build panels that fold out anyway. Why not just tuck them in and box them up before you hit the martian atmosphere?

If you're going to the trouble of using electric propulsion you need to justify it with much higher delta V's, when that happens aerocapture becomes proportionately less useful.
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Offline HailColumbia

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Re: VASIMR Engine
« Reply #61 on: 12/14/2014 12:25 AM »

If you're going to the trouble of using electric propulsion you need to justify it with much higher delta V's, when that happens aerocapture becomes proportionately less useful.

Don't you still get to spend less time decelerating regardless? Seems like aerocapture would always be the most efficient option, assuming your spacecraft is not made of aluminum foil and twine.
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Offline Alf Fass

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Re: VASIMR Engine
« Reply #62 on: 12/14/2014 12:39 AM »
To go faster your craft needs to be lighter, if we use an exhaust velocity of 100km/sec as an example, kg for kg extra propellant will get you a quicker trip than that mass in the form of PicaX (the Dragon heatshield material) assuming the power supply problems in hand.
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Offline Dalhousie

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Re: VASIMR Engine
« Reply #63 on: 12/14/2014 01:48 AM »
The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

And with nuclear electric getting the radiators to do the same.
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Offline savuporo

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Re: VASIMR Engine
« Reply #64 on: 12/14/2014 03:15 AM »
it bears to mention that todays practical chemical propulsion beyond earth departure burns is around 325 ISP or so. storable hyprgolics only.

so when comparing theoretical benefits of SEP vs VASIMR vs chemical, this has to be kept in mind.
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Offline guckyfan

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Re: VASIMR Engine
« Reply #65 on: 12/14/2014 08:06 AM »
The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

I suppose you could abandon the VASIMR its solar panels, and aerocapture the rest of the craft.

Seems a bit of a waste.

Wouldn't retractable panels solve this problem?  Given the surface area needed for something like VASIMR you have to build panels that fold out anyway. Why not just tuck them in and box them up before you hit the martian atmosphere?

Retractable would add a lot of weight. My guess would be to separate payload and SEP propulsion. Let the payload do aerocapture or landing and the propulsion system can do propulsive capture, now that it is much lighter.


Online MP99

Re: VASIMR Engine
« Reply #66 on: 12/14/2014 05:38 PM »


The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

I suppose you could abandon the VASIMR its solar panels, and aerocapture the rest of the craft.

Seems a bit of a waste.

Wouldn't retractable panels solve this problem?  Given the surface area needed for something like VASIMR you have to build panels that fold out anyway. Why not just tuck them in and box them up before you hit the martian atmosphere?

Retractable would add a lot of weight. My guess would be to separate payload and SEP propulsion. Let the payload do aerocapture or landing and the propulsion system can do propulsive capture, now that it is much lighter.

gf,

I really should pay more attention to the posts I'm replying to. I just composed exactly that suggestion. At least I re-read your post before I submitted. With it understood that you beat me to it, I might as well post it anyway:-

Have the VASIMR subsystem so it can separate from the spacecraft?

Spacecraft does aerocapture, while VASIMR performs its own deceleration and returns itself to Mars orbit. Fuel requirements would be reduced due to having to accelerate much less mass. Call it an in-space tug, if you like.

The returning spacecraft ascends, docks back with the VASIMR, which propels it back to Earth. The VASIMR would only be dead weight during the descent & ascent, and at unnecessary risk of damage.

Downside:- VASIMR is not immediately available if the landing is aborted. However, the return journey could be accomplished by a second VASIMR which is pre-positioned at LMO. This might mean the stage could have higher perf, since it's carrying much less mass for one of the two legs.

Cheers, Martin

Offline TrevorMonty

Re: VASIMR Engine
« Reply #67 on: 12/14/2014 06:43 PM »


The trick with aerocapture and solar electric propulsion is getting the featherweight solar collectors to survive the aerocapture maneuver.

I suppose you could abandon the VASIMR its solar panels, and aerocapture the rest of the craft.

Seems a bit of a waste.

Wouldn't retractable panels solve this problem?  Given the surface area needed for something like VASIMR you have to build panels that fold out anyway. Why not just tuck them in and box them up before you hit the martian atmosphere?

Retractable would add a lot of weight. My guess would be to separate payload and SEP propulsion. Let the payload do aerocapture or landing and the propulsion system can do propulsive capture, now that it is much lighter.

gf,

I really should pay more attention to the posts I'm replying to. I just composed exactly that suggestion. At least I re-read your post before I submitted. With it understood that you beat me to it, I might as well post it anyway:-

Have the VASIMR subsystem so it can separate from the spacecraft?

Spacecraft does aerocapture, while VASIMR performs its own deceleration and returns itself to Mars orbit. Fuel requirements would be reduced due to having to accelerate much less mass. Call it an in-space tug, if you like.

The returning spacecraft ascends, docks back with the VASIMR, which propels it back to Earth. The VASIMR would only be dead weight during the descent & ascent, and at unnecessary risk of damage.

Downside:- VASIMR is not immediately available if the landing is aborted. However, the return journey could be accomplished by a second VASIMR which is pre-positioned at LMO. This might mean the stage could have higher perf, since it's carrying much less mass for one of the two legs.

Cheers, Martin
Separating payload for aero capture makes sense.

There was a comment earlier about solar arrays designed for launch being to heavy. Technologies are in development to enable solar arrays to be built in space. See Tethers Unlimited Spider truss. In space assembly means support structures can be feather light as forces on them are <0.1g especially for SEP.

Offline TrevorMonty

Re: VASIMR Engine
« Reply #68 on: 12/14/2014 07:47 PM »
Here is article on ultra light solar arrays. This is from 2004?

They were talking 4.5kw/kg for rollable panels. I would like to know what it is now.


http://www.spacefuture.com/archive/early_commercial_demonstration_of_space_solar_power_using_ultra_lightweight_arrays.shtml



Offline savuporo

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Re: VASIMR Engine
« Reply #69 on: 12/14/2014 07:58 PM »
Here is article on ultra light solar arrays. This is from 2004?

They were talking 4.5kw/kg for rollable panels. I would like to know what it is now.

http://cms.atk.com/SiteCollectionDocuments/ProductsAndServices/UltraFlex-2012.pdf

EDIT: in short, about 200w/kg. This has been scaled up to 8m diameter wings, called Megaflex
http://www.nasa.gov/offices/oct/home/feature_sas_prt.htm

The next step advancement can come from separating the deployment system from the actual arrays. Similar to how some terrestrial solar farms got rid of expensive per-panel tracker motors and leave it to a separate rail-running robotic device.

http://www.qbotix.com/rts/
« Last Edit: 12/14/2014 08:19 PM by savuporo »
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Offline A_M_Swallow

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Re: VASIMR Engine
« Reply #70 on: 12/14/2014 08:09 PM »

Have the VASIMR subsystem so it can separate from the spacecraft?

Spacecraft does aerocapture, while VASIMR performs its own deceleration and returns itself to Mars orbit. Fuel requirements would be reduced due to having to accelerate much less mass. Call it an in-space tug, if you like.

The returning spacecraft ascends, docks back with the VASIMR, which propels it back to Earth. The VASIMR would only be dead weight during the descent & ascent, and at unnecessary risk of damage.

Downside:- VASIMR is not immediately available if the landing is aborted. However, the return journey could be accomplished by a second VASIMR which is pre-positioned at LMO. This might mean the stage could have higher perf, since it's carrying much less mass for one of the two legs.

Cheers, Martin

The second inspace tug could have brought cargo so it would have been discarded or returned empty.

If you are planning a series of missions then arrange to have an abort VASIMR waiting in Mars orbit.  The current tug becomes the next abort VASIMR.

Offline TrevorMonty

Re: VASIMR Engine
« Reply #71 on: 12/14/2014 09:21 PM »
Here is article on ultra light solar arrays. This is from 2004?

They were talking 4.5kw/kg for rollable panels. I would like to know what it is now.

http://cms.atk.com/SiteCollectionDocuments/ProductsAndServices/UltraFlex-2012.pdf

EDIT: in short, about 200w/kg. This has been scaled up to 8m diameter wings, called Megaflex
http://www.nasa.gov/offices/oct/home/feature_sas_prt.htm

The next step advancement can come from separating the deployment system from the actual arrays. Similar to how some terrestrial solar farms got rid of expensive per-panel tracker motors and leave it to a separate rail-running robotic device.

http://www.qbotix.com/rts/
The Megaflex is designed to be compact and handle launch loads. A lot of their weight and expense is in structure plus they a limited by area efficiency (kw/m2 30%?) of solar arrays as they need to be compact.

Solar arrays that assembled in space can be less efficient by area 6-9% for rollable 4.5kw/kg example. The rolled up array ( think roll of paper) is still compact for launch as there is no structure. The idea is to add it to lightweight structure that is built in space. With in space assembly arrays of square kms is not an issue as the only load is SEP thrust. The article was quoting 1kW/kg for arrays, structure and power systems, that is 200kg for 200kw. We still a years away but not decades from in space assembly.

Offline savuporo

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Re: VASIMR Engine
« Reply #72 on: 12/14/2014 10:12 PM »
i thought ISS was assembled in space last decade already. DEXTRE has demoed unmanned assembly and repair ops as well.
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Offline A_M_Swallow

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Re: VASIMR Engine
« Reply #73 on: 12/14/2014 11:37 PM »

The Megaflex is designed to be compact and handle launch loads. A lot of their weight and expense is in structure plus they a limited by area efficiency (kw/m2 30%?) of solar arrays as they need to be compact.

Solar arrays that assembled in space can be less efficient by area 6-9% for rollable 4.5kw/kg example. The rolled up array ( think roll of paper) is still compact for launch as there is no structure. The idea is to add it to lightweight structure that is built in space. With in space assembly arrays of square kms is not an issue as the only load is SEP thrust. The article was quoting 1kW/kg for arrays, structure and power systems, that is 200kg for 200kw. We still a years away but not decades from in space assembly.

So the biggest thrust is likely to be chemical thrusters in the RCS.  Easy to handle providing the designers are warned that the thrust is coming.

Offline L5Resident

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Re: VASIMR Engine
« Reply #74 on: 12/21/2014 08:07 PM »
Is VASIMR still going on the station? I haven't heard much of anything recently.

Offline ChrisWilson68

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Re: VASIMR Engine
« Reply #75 on: 12/21/2014 09:12 PM »
Is VASIMR still going on the station? I haven't heard much of anything recently.

I don't think so.

The last news we heard was the June 2014 Aviation Week article:

""We are kind of stuck," says Franklin Chang-Diaz, Ad Astra CEO and president. The company's current SAA expires in early December. Chang-Diaz says the project is unlikely to advance further without a NASA-funded SAA successor, one the company would prefer to structure like the 2005 Commercial Orbital Transportation Services initiative that spawned Falcon 9/Dragon and Orbital Sciences' Antares/Cygnus ISS resupply services." - June 2014, Aviation Week

Apparently they need about $11 million.

This says the project needs more NASA money or it can't progress after early December.  Since we haven't heard them announcing any new money from NASA or anywhere else, the logical conclusion is that VASIMIR is dead and won't be going to the station.

It's a pity.

Online Stormbringer

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Re: VASIMR Engine
« Reply #76 on: 12/21/2014 10:08 PM »
Dr Diaz did some crownd funding to get funds to keep the program going for a while and to produce a couple of promotional videos and develop mission plans. also the wiki still has the ISS mission but with pushed back dates.

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

Quote
Testing on the International Space Station

On December 8, 2008, Ad Astra signed an agreement with NASA to arrange the placement and testing of a flight version of the VASIMR, the VF-200, on the International Space Station (ISS).[24] In early 2009, the earliest possible launch date was reported as 2012.[25] As of April 2014, its launch is anticipated to be in 2016.[26] The reason for the delays have been attributed to funding; and in June 2014, Franklin Chang-Diaz stated that the project is unlikely to proceed unless they're able to receive a funded-SAA from NASA.[27]
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Online QuantumG

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Re: VASIMR Engine
« Reply #77 on: 12/21/2014 10:13 PM »
Dr Diaz did some crownd funding

Just like Christopher Columbus!

To be fair, this has to be the longest running rocket development program - that hasn't produced anything - of all time.
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Offline Raj2014

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Re: VASIMR Engine
« Reply #78 on: 12/21/2014 10:35 PM »
Dr Diaz did some crownd funding

Just like Christopher Columbus!

To be fair, this has to be the longest running rocket development program - that hasn't produced anything - of all time.

They have done a lot of work on the VASIMR. If you look on ad astra rocket website and youtube, you will see a lot of information and videos, which shows them testing VASIMR. VASIMR has been mentioned in a lot websites and documentaries. I hope they can raise the money they need to continue testing and hopefully it will lead to deep space travel. 

Online QuantumG

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Re: VASIMR Engine
« Reply #79 on: 12/21/2014 10:36 PM »
They have done a lot of work on the VASIMR.

No doubt. What they haven't done is produce a rocket engine.
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