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.
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.
And the assumptions for the array specific power are very conservative.
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.
– 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.
http://www.parabolicarc.com/2011/09/15/nasa-selects-companies-to-study-solar-electric-propulsion-spacecraft/#more-29549QuoteNASA 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
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.
Quote from: A_M_Swallow on 09/29/2011 04:33 amProviding 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.
Quote from: Solman on 09/29/2011 11:08 pmQuote from: A_M_Swallow on 09/29/2011 04:33 amProviding 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-1228by Takashi Nakamura et al.http://www.psicorp.com/pdf/library/sr-1228.pdf
Quote from: A_M_Swallow on Today at 01:49:08 Quote 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.pdfMy 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.
from: A_M_Swallow on Today at 01:49:08 Quote 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
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
QuoteNASA 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.
Transfer of supercritical propellant in-space is non-trivial. It would likely be easier to just have swapable propellant tanks.
Quote from: simonbp on 01/19/2012 05:39 amTransfer 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 ?
