Author Topic: Solar Electric Propulsion for a Flexible Path of Human Space Exploration  (Read 44588 times)

Offline Robotbeat

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http://multimedia.seti.org/PhD2011/abstracts/PhD2-11-011.pdf
http://multimedia.seti.org/PhD2011/presentations/3-Human%20Exploration%20Session/PhD2-2011-Landau-Talk-[11-011].pdf
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We present an architecture for Human missions to Phobos and Deimos in the 2030s using Solar Electric Propulsion (SEP).  These missions would be an extension of near-Earth asteroid missions using similar hardware in the 2020s.  The concept relies on taking existing, flight-proven technologies from unmanned spaceflight and scaling them up to higher power levels for human spaceflight.  When applied to human spaceflight, the robustness of SEP trajectories and the lack of time critical events significantly enhance mission safety for astronauts.  This is accomplished by using SEP boost stages to pre-position a Deep Space Vehicle (DSV), supplies, and chemical boost stages in High Earth Orbit (HEO).  Pre-placing these elements in HEO for later crew rendezvous avoids having the crew onboard the DSV during the 1–2 year long, low-thrust parts of the trajectory, while still taking advantage of the high fuel efficiency of solar electric propulsion systems.

Once these assets are pre-placed in HEO, a lunar flyby is used to drop the perigee of the DSV to the altitude of International Space Station (ISS) orbit.  Astronauts are then launched from the ISS to rendezvous with the DSV in an Orion Crew Module using a chemical boost stage.  Once the crew establishes that the DSV is ready for departure from HEO the DSV performs an Earth escape burn with a chemical boost stage. After Earth departure, the crew uses the SEP stage as part of the DSV to rendezvous with Deimos then Phobos for an accumulated orbit time of four months. Following rendezvous, the DSV returns to Earth using the SEP stage and the astronauts depart in the Orion Crew Module for a direct entry.  After the crew returns, the unmanned DSV uses the SEP stage to return to HEO over the course of a year where it is refurbished for reuse on a subsequent mission.

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Observations
• SEP reduces launch mass for missions ranging
from cis-lunar excursions, to NEO encounters, to
Phobos & Deimos rendezvous
• Power levels of 100-600 kW enable SEP missions
with IMLEO comparable to NTR technology with
similar flight times. 
• There are many paths from cis-lunar missions to
Mars through the NEO capability design space
• The evolution of SEP from current levels
introduces flexibility on an exploration path to
Mars.

What is interesting to me is that 100-600kW is about the range of the proposed Solar-electric Propulsion demo, slated at ~400kW. That means the "demo" could easily be used for real manned missions to Mars orbit (and, paired with pre-placed Mars landers, Mars surface), NEOs, etc (besides the obvious cis-lunar applications).

EDIT:Another interesting thing is that it kicks NTR's butt when it comes to delivering cargo to Mars for a given IMLEO, and gets over twice the payload to Mars's atmospheric interface compared to chemical for a given IMLEO. And the assumptions for the array specific power are very conservative. Another interesting thing is that total IMLEO for a Phobos mission can be less than 300mT (with a mission duration of ~2.5 years). That means the average annual per-year IMLEO would be less than 130mT per year for a Phobos mission. HLV optional.
« Last Edit: 08/11/2011 10:47 pm by Robotbeat »
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Offline Hop_David

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And the assumptions for the array specific power are very conservative.

What specific power did they assume? I didn't see that mentioned on the documents you linked to.

Offline manboy

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Is the pdf using short tons?
"Cheese has been sent into space before. But the same cheese has never been sent into space twice." - StephenB

Offline A_M_Swallow

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From page 7 of the talk .pdf

"15% inert/propellant, 30 kg/kW"

For 100 t IMLEO launch using 600kW, 3000 s SEP taking 1.5 years to Mars delivering a mass of 52.8 t to the atmospheric interface.

(Other flight times and mass are possible.)

Offline Ronsmytheiii

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http://www.parabolicarc.com/2011/09/15/nasa-selects-companies-to-study-solar-electric-propulsion-spacecraft/#more-29549

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NASA has selected five companies to develop concepts for demonstrating solar electric propulsion in space. These capabilities are important for the agency’s future human exploration missions to deep space.

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– Analytical Mechanics Associates Inc., Hampton, Va.
– Ball Aerospace & Technologies Corp., Boulder, Colo.
– The Boeing Company, Huntington Beach, Calif.
– Lockheed Martin Space Systems Company, Littleton, Colo.
– Northrop Grumman Systems Corp., Redondo Beach, Calif.

Image url:

http://www.ama-inc.com/images/stories/landscape_large.jpg
« Last Edit: 09/15/2011 10:08 pm by Ronsmytheiii »

Offline Robotbeat

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Awesome. This will pay dividends in making human exploration architectures a lot more flexible. And lower cost, especially for large missions (like Mars surface) and/or for continual resupply of depots or outposts (if that is ever done).
« Last Edit: 09/15/2011 10:46 pm by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Robotbeat

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http://www.parabolicarc.com/2011/09/15/nasa-selects-companies-to-study-solar-electric-propulsion-spacecraft/#more-29549

Quote
NASA has selected five companies to develop concepts for demonstrating solar electric propulsion in space. These capabilities are important for the agency’s future human exploration missions to deep space.

Quote
– Analytical Mechanics Associates Inc., Hampton, Va.
– Ball Aerospace & Technologies Corp., Boulder, Colo.
– The Boeing Company, Huntington Beach, Calif.
– Lockheed Martin Space Systems Company, Littleton, Colo.
– Northrop Grumman Systems Corp., Redondo Beach, Calif.

Image url:

http://www.ama-inc.com/images/stories/landscape_large.jpg
Is there a NASA.gov link for this?
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Solman

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 Provided a large parabolic concentrator mirror is used to concentrate sunlight onto triple junction or other type of PV to generate the electricity for SEP; the possibility of direct use of the concentrated sunlight for solar thermal rocket propulsion is a side benefit in addition to the 40% or better conversion efficiency of this type of PV. Advantages include higher specific power for the electric generation and the higher thrust for orbit raising from low to highly elliptical orbit of the solar thermal rocket to speed this up vs. electric albeit at lower Isp.
 A mix of thermal and electric can provide a wide range of Isp as well. While hydrogen is best and lithium second best, solar thermal can use almost anything as propellant including direct use of NEO regolith even if that's all that's available. The concentrator mirror can double as a communications or radar antenna.

Steve

Offline A_M_Swallow

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Providing it uses the same propellant solar thermal may be better for the RCS (Reaction Control System) than ion thrusters.  RCS burns tend to be short where as SEP works better for extra long burns.  I suspect that both can use Argon and nitrogen.

Offline Solman

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Providing it uses the same propellant solar thermal may be better for the RCS (Reaction Control System) than ion thrusters.  RCS burns tend to be short where as SEP works better for extra long burns.  I suspect that both can use Argon and nitrogen.

 I remember seeing a paper from the Nineties that described a small working model of a solar thermal rocket concentrator that used fiberoptic cables to route the focussed sunlight to the engine.
 This might be a good design for RCS thrusters using solar thermal.



Offline A_M_Swallow

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Providing it uses the same propellant solar thermal may be better for the RCS (Reaction Control System) than ion thrusters.  RCS burns tend to be short where as SEP works better for extra long burns.  I suspect that both can use Argon and nitrogen.

 I remember seeing a paper from the Nineties that described a small working model of a solar thermal rocket concentrator that used fiberoptic cables to route the focussed sunlight to the engine.
 This might be a good design for RCS thrusters using solar thermal.


Probably this article.
"Solar Thermal Propulsion for Small Spacecraft" PSI-SR-1228
by Takashi Nakamura et al.
http://www.psicorp.com/pdf/library/sr-1228.pdf

Offline Solman

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Providing it uses the same propellant solar thermal may be better for the RCS (Reaction Control System) than ion thrusters.  RCS burns tend to be short where as SEP works better for extra long burns.  I suspect that both can use Argon and nitrogen.

 I remember seeing a paper from the Nineties that described a small working model of a solar thermal rocket concentrator that used fiberoptic cables to route the focussed sunlight to the engine.
 This might be a good design for RCS thrusters using solar thermal.


Probably this article.
"Solar Thermal Propulsion for Small Spacecraft" PSI-SR-1228
by Takashi Nakamura et al.
http://www.psicorp.com/pdf/library/sr-1228.pdf

 Thanks for the link. Carried to an extreme, fiber optics could be used to distribute heat and light to wherever its needed in a spacecraft. Perhaps the cable could be designed to shift the many frequencies of sunlight into a single frequency as it travels down the fiber optic line and deliver it to a PV element at the point where a device needs electricity. The PV element would be very efficient since it could be designed for a single frequency. The fiber optics could also provide data transfer and control of course. Cutting and welding using concentrated sunlight delivered by fiber optics also a possibility I would think.
 Large concentrators also enable a solar furnace for ISRU and they can double as microwave transmitters for space based power transmission between spacecraft or down to the surface of Mars for instance. They can be formed by a technique I call inflation insituform with degradable elements in which some parts harden when exposed to the Sun's UV light and other parts degrade. The finished product can be optimized for low mass - high specific power and can achieve very high temperatures if adjusted by built-in actuators both as it forms and thereafter. Or at least it seems practical to me.
 Another advantage of PV for concentrated sunlight is that the cells must be actively cooled and the resulting waste heat is useful for keeping spacecraft warm. This means nearly 100% of the intercepted sunlight is used compared to a regular PV array which must use some of its electricity to provide resistance heat and has lower efficiency to begin with. The support structure for the concentrator can be at least partially made of hollow tubes that could double as waste heat radiators perhaps.

Steve

Offline A_M_Swallow

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From the "Re: POLL: Are you supportive of the Prop Depot Concept?" thread reply #121.
http://forum.nasaspaceflight.com/index.php?topic=27297.msg832919#msg832919

Xplor wrote
Quote
Quote
from: A_M_Swallow on Today at 01:49:08

   
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from: Xplor on 24 November 2011, 13:24:01

        For those suggesting starting with SEP, what power level are you proposing?
        1) 10's of Kw
        2) 100's of Kw
        3) 1,000's of Kw

    For a working vehicle - this decade - buy as much as possible off the shelf so 10's of kW.
    Two of the ATK Ultraflex built for the Orion will supply 12 kW and four 24 kW.  There are several Hall Thrusters in that range.
    http://www.aiaa.org/pdf/industry/presentations/AIAA_IECEC_Final_Anderson_7_20_10_Nashville.pdf

My fear of SEP is that NASA will continue down their 100's kw path leading to another multi-billion dollar development/infrastructure demand.   “The flight demonstration mission would test and validate key capabilities and technologies required for future exploration elements such as a 300 kilowatt solar electric transfer vehicle.”

Deriving SEP from today's communication satellites may provide affordable SEP and  benefit America's satellite industry.  This is similar to the arguments in favor of using EELV class launch vehicles.

IMHO.  A large SEP tug will be needed to transport propellant to Mars but a small and cheaper SEP tug can be used as a test bed to develop the tugs systems.

Offline A_M_Swallow

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NASA has selected five companies to develop concepts for demonstrating solar electric propulsion in space. These capabilities are important for the agency’s future human exploration missions to deep space.

Any information on when these studies are going to be published?

Offline AnalogMan

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A recent paper which may be of interest to this thread:

Concept Design of High Power Solar Electric Propulsion Vehicles for Human Exploration
62nd International Astronautical Congress NASA/TM—2011-217281 published 1Dec11 16pp

Human exploration beyond low Earth orbit will require enabling capabilities that are efficient, affordable and reliable. Solar electric propulsion (SEP) has been proposed by NASA’s Human Exploration Framework Team as one option to achieve human exploration missions beyond Earth orbit because of its favorable mass efficiency compared to traditional chemical propulsion systems. This paper describes the unique challenges associated with developing a large-scale high-power (300-kWe class) SEP vehicle and design concepts that have potential to meet those challenges. An assessment of factors at the subsystem level that must be considered in developing an SEP vehicle for future exploration missions is presented. Overall concepts, design tradeoffs and pathways to achieve development readiness are discussed.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120000068_2011025608.pdf

Offline A_M_Swallow

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A reusable SEP tug needs the ability to be refuelled in orbit and to accept new cargoes.  This process can be tested with a 30 kW tug.  The tugs second mission could take a real cargo to GSO or EML-1.

Offline simonbp

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

Offline Archibald

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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 ?
Han shot first and Gwynne Shotwell !

Offline alexw

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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

Offline Robotbeat

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Transfer liquid Xenon instead. As a bonus, the tanks will be smaller and much, much lighter for the same amount of propellant.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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