Solar Electric Propulsion for a Flexible Path of Human Space Exploration

[A_M_Swallow]

Transfer liquid Xenon instead. As a bonus, the tanks will be smaller and much, much lighter for the same amount of propellant.

First check to see if you can use the much cheaper Argon.

[Archibald]

Transfer of supercritical propellant in-space is non-trivial. It would likely be easier to just have swapable propellant tanks.

NASA did a lot of work on superfluid helium transfer in the 80's - when Spitzer was to be refilled to extend its useful life. How hard would it be to transfer helium in zero G ?

    Supercritical fluid != Superfluid.

    Also, how far did such plans with Spitzer get?
                                   -Alex

I have difficulties understanding the difference between the two !

About Spitzer (formerly SIRTF, for Shuttle / Spacelab / Space InfraRed Telescope Facility):
It started as a Spacelab telescope, then moved to a polar orbit free flyer. The manned servicing capability was lost after 1990 in the multiple cuts that shrunk Spitzer from shuttle / Titan IV to Atlas II then to Delta II.
Long after the dust settled in 1993 a shuttle mission STS-57 carried a SuperFluid Helium On Orbit Transfer experiment - SHOOT.
http://cryo.gsfc.nasa.gov/SHOOT/STS57.html

[Robotbeat]

Supercritical just means the pressure and temperature are both high enough that there's no longer a solid line between gas and liquid... Supercritical is an in-between phase.

Superfluid means there's no viscosity at all (though with enough effort, you can form these weird quantized vortex things). It's a quantum mechanical effect that's really weird. Superconductivity happens when the electrons in a material enter a superfluid state. In regular matter (and other than electrons), it pretty much only happens with liquid helium.

[alexw]

Long after the dust settled in 1993 a shuttle mission STS-57 carried a SuperFluid Helium On Orbit Transfer experiment - SHOOT.
http://cryo.gsfc.nasa.gov/SHOOT/STS57.html

Thanks for that reference.
"The porous plugs used in SHOOT were manufactured by Coors, a company which has been making porous filters for many years. Lately, they have branched out as a manufacturer of dilute ethanol solutions, which they filter by pumping them through their own porous filters."
       -Alex

[yg1968]

A couple of articles on the topic:
http://www.aviationweek.com/Article.aspx?id=/article-xml/AW_05_28_2012_p20-460440.xml&p=1
http://aerospace.engin.umich.edu/newsevents/northrop-grumman-tapped-by-nasa-to-develop-solar-electric-propulsion-flight-concepts-for-future-space-missions

[A_M_Swallow]

They will have to change the name of the arrays, MegaFlex is already the name of a UK company.

[Prober]

Transfer liquid Xenon instead. As a bonus, the tanks will be smaller and much, much lighter for the same amount of propellant.

just started looking into an upgrade for the ISS stationkeeping.  Wonder if Xenon based thrusers could do the job?
 
Could the 702SP satellites, or 702HP be the starting point?
http://www.boeing.com/defense-space/space/bss/factsheets/702/702fleet.html
 
Further efficiency derives from the 702's advanced xenon ion propulsion system (XIPS), which was pioneered by Boeing.  XIPS is 10 times more efficient than conventional liquid fuel systems. Four 25-cm thrusters provide economical stationkeeping, needing only 5 kg of fuel per year - a fraction of what bipropellant or arcjet systems consume.

[pathfinder_01]

 
just started looking into an upgrade for the ISS stationkeeping.  Wonder if Xenon based thrusers could do the job?
 

Bad idea. The thrusters could cancel out the microgravity the station wants. They would induce a constant or near constant acceleration. There are plans to test VASIMR at the station and it would cancel out drag a bit but it would only run for short burst both due to power issuses and microgravity issues.

[Robotbeat]

 
just started looking into an upgrade for the ISS stationkeeping.  Wonder if Xenon based thrusers could do the job?
 

Bad idea. The thrusters could cancel out the microgravity the station wants. They would induce a constant or near constant acceleration. There are plans to test VASIMR at the station and it would cancel out drag a bit but it would only run for short burst both due to power issuses and microgravity issues.

If you did it just right, it's possible to get /better/ microgravity on ISS using electric thrusters.

[deltaV]

According to the Keck study on asteroid moving (http://www.kiss.caltech.edu/study/asteroid/asteroid_final_report.pdf) (italics added):

Near-Term Application of SEP Technology for Human Missions to NEAs
The development of a 40 kW-class SEP system would provide the valuable capability of being able to pre-deploy several tons of destination elements, logistics, and payloads. Initial estimates identify that approximately 3,100 kg of elements and logistics, along with approximately 500 kg of destination payload, could be pre-deployed in support of a human NEA mission, rather than carried with the crew.
This approach would reduce the requirements for the launch vehicles and in-space propulsive elements required to conduct a human mission. The amount of mass that could be pre-deployed along with the SEP system is primarily a function of the launch vehicle utilized, the orbital energy requirements of the NEA target, the efficiency of the SEP system, and the desired amount of returned mass. Although a SEP system and associated cargo could be delivered to low-Earth orbit (LEO) by the launch vehicle and spiraled out to escape the Earth’s gravity, the time required to perform this operation along with the radiation and micrometeoroid and orbital debris (MMOD) exposure resulting from the spiral from LEO would make it desirable for the launch vehicle to be able to propel the SEP system and payload to an escape C3. Additionally, since the departure windows for accessible NEAs could be short and since it is likely that pre-deployed assets would be required to be at NEA prior to crew departure from Earth, the duration of the pre-deploy mission would be a critical factor.

The italicized text contrasts with other proposals that use SEP to bring cargo from LEO to EML-2, e.g. http://www.nasaspaceflight.com/2013/01/boeing-outlines-technology-crewed-mars-missions/. The concern about launch windows seems strange since the SEP tug could be launched and sent spiraling out well before the departure window and timed so that C3=0 is reached at the appropriate time. Is the radiation and MMOD concern a big deal? Is NASA likely to use SEP to spiral HSF components out from LEO?

Developing both large-scale SEP technology and an SLS upper stage sounds difficult given expected budgets. Wouldn't it be better to just develop one of the two? If you have SEP that works from LEO you could probably get by without an SLS upper stage except for a small existing one (e.g. ICPS) to send MPCV towards EML-2. Alternatively skip the SEP, crank up the IMLEO, and build an upper stage/EDS to throw stuff towards EML-2. Thoughts?

Related thread on SEP: http://forum.nasaspaceflight.com/index.php?topic=28115.0 .

[sdsds]

I'm not clear whether everyone discussing the use of electric propulsion to spiral out of LEO means the same thing. In the simplest case of starting in a circular LEO and applying continuous thrust, each successive orbit in the spiral gets larger but they are all circular. Marco Christov though discusses thrusting only at perigee and thus the orbits in his spirals are successively more eccentric ellipses.

These two approaches might be substantially different in relation to passing through the Van Allen belts and thus the question of whether radiation is a big deal or not. Also, the Van Allen belts do vary quite a bit. There's a great video at:
http://www.nature.com/news/ephemeral-third-ring-of-radiation-makes-appearance-around-earth-1.12529

[Robotbeat]

http://spirit.as.utexas.edu/~fiso/telecon/Oleson_3-6-13/Oleson_3-6-13.pdf
http://spirit.as.utexas.edu/~fiso/telecon/Oleson_3-6-13/Oleson.mp3
"Combined SEP-Chemical for Piloted Mars Missions"

(Has anyone posted this yet?)

BTW, this guy is the lead at Glenn for the group who thought up how to bag an asteroid. COMPASS is a pretty sweet group. They have a bunch of people in a room, one person per subsystem (one comms, one for power, one for structures, one for cost, one driving CAD, etc...) sitting at a computer station and all working together, with Steve at the middle leading everyone. There are projectors displaying the lead's display on three walls, plus a couple of rapid prototyping machines for getting an idea of the spacecraft structures. One of the coolest places I've been at Glenn, it looks like exactly where spaceships ought to be born.

EDIT:Yes, this has been posted before:
http://forum.nasaspaceflight.com/index.php?topic=29918.msg1024104#msg1024104

[deltaV]

Studies comparing mass efficiency (IMLEO) of solar electric and chemical in-space propulsion (for human missions) are dime a dozen. Are there any studies that compare cost and schedule of SEP vs. chemical? Basically I'm looking for a study like the Augustine Report but focusing on in-space propulsion instead of launch vehicles.

[Hop_David]

Studies comparing mass efficiency (IMLEO)

What's IMLEO stand for? I recall NSF used to have a list of abbreviations. For me that was very helpful in making sense of the alphabet soup. But I can't find it at the moment.

[Lee Jay]

Studies comparing mass efficiency (IMLEO)

What's IMLEO stand for? I recall NSF used to have a list of abbreviations. For me that was very helpful in making sense of the alphabet soup. But I can't find it at the moment.

Initial (or insertion?) Mass to Low Earth Orbit.

[savuporo]

Sandia and NG were working on Brayton cycle power conversion
http://energy.sandia.gov/?page_id=14240
Whatever happened to that ?

The grant was here http://www.spaceref.com/news/viewpr.html?pid=35890

[Robotbeat]

Sandia and NG were working on Brayton cycle power conversion
http://energy.sandia.gov/?page_id=14240
Whatever happened to that ?

The grant was here http://www.spaceref.com/news/viewpr.html?pid=35890

They're probably still working on it, back-burner-ish. Stuff like that tends to sit around in a warehouse until someone gets another grant to continue work.

[rusty]

** Updates **

Jan 17th - http://www.nasa.gov/press/2014/january/nasa-administrator-surveys-agencys-work-in-advanced-propulsion-technologies/
"Glenn Center Director Jim Free guided Bolden, U.S. Senator Sherrod Brown and U.S. Rep. Marcia Kaptur, both of Ohio, on a tour of Glenn’s Electric Propulsion Laboratory, which houses a large space environment simulation chamber. The chamber is being enhanced for future testing of solar electric propulsion technologies ...
Later this year, NASA and its commercial partners will mark another milestone in industry partnerships when it tests at Glenn the large solar array system to demonstrate the structural integrity of large array designs that one day will support advanced SEP."

Jan 22nd - http://www.satellitetoday.com/technology/2014/01/22/atk-demonstrates-megaflex-solar-array-for-nasa/
"ATK has deployed its Solar Electric Propulsion (SEP) MegaFlex solar array under a NASA contract to further the development of a high-power system for future manned and robotic exploration missions.
The MegaFlex solar array can generate 40kW of power when fully populated with solar cells, and ... is based on ATK’s UltraFlex platform that powered NASA’s Mars Phoenix Lander in 2008."

Mar 6th - http://www.sacbee.com/2014/03/06/6215607/nasa-officials-to-view-new-solar.html
"NASA Administrator Charles Bolden and Associate Administrator for Space Technology Michael Gazarik will visit the agency's Glenn Research Center's Plum Brook Station Wednesday, March 12, to see an advanced solar array system being tested at the facility. ...
NASA selected ATK and Deployable Space Systems (DSS), both of Goleta, Calif., in 2012 to develop advanced solar systems to support advanced solar electric propulsion. DSS expects to test its system later this year."
--------------------------------------------------------------------------------

What ever happened with the contracts originally proposed by this thread? Are these three stories related as I've shown, or separate? Was this a different contract award than the OP's, or were those slimmed down until only this outsider was approved? Are there still other ongoing contracts?

[Robotbeat]

Cool, didn't know they were testing the array at Plum Brook already. Neat facility. So are the other vacuum chambers at Glenn (they've a vacuum chamber at Glenn that's been being used for years on end to endurance test the NEXT thruster... I have a picture somewhere).

[rusty]

Anyone familiar with or can provide studies on Lunar SEP?
Everything I've read focuses on either deep-space missions or LEO to EML/LLO, but I haven't seen anything on using SEP for only Lunar orbit maneuvers or just EML to LLO. In these instances, cargo would be launched to or through EML where SEP would direct it into its final Lunar orbit, then return for the next. This severally cuts down transit time, avoids Van Allens, reduces thrust requirements and I think is the best use for tugs. Thank You.