Patchouli - 28/3/2008 4:42 PMIf they switch Altair to storable propellants and a private group builds a lander that uses them I think it also could make use of a solar electric tug to replace the EDS for some missions.Use of the solar or nuclear electric tug wouldn't be for manned mission but for cargo missions such as hab sections,vehicles, and bulk cargo.
Major 2007 milestones achieved includedkey results from a newly operationalVASIMR™ 100kW test bed, the VX-100and initiation of manufacturing andsubsystem integration for the first flight-likeengine prototype, the 200kW VX-200. Inaddition, the company signed importantagreements with NASA and NAUTEL Ltdof Canada.>An initial test firing of the full engineprototype has been postponed until the 2ndquarter of 2008 in order to give ScientificMagnetics of Culham, UK. the needed timeto complete its certification of thesuperconducting subsystem. This is a criticalcomponent of the engine, which the Britishcompany is building under contract with AdAstra.
Patchouli - 28/3/2008 4:00 PMThis engine claims to be 10x more efficient then smart 1's engine whch should give it an ISP of 27,000.http://www.physorg.com/news9786.htmlEven if it only proves to be twice as efficient in practice it will make a reusable tug very practical.
alexterrell - 29/3/2008 11:11 PMIf it has 10 times the ISP, then it needs 1/10 the propellant, but 10 TIMES THE ENERGY. (OK, maybe 8 times if its 70% efficient).That means it needs 8 times the solar power, or 8 times as long, or some combination of the two.
meiza - 30/3/2008 4:50 PMUmm, the energy costs mass and expensive hardware. You end up with either lower payload fraction or lower acceleration.
A_M_Swallow - 28/3/2008 10:27 PMMore fuel is needed if the ferry is reusable. The ferry could have been lifted off the Earth on a different Launch Vehicle. This report estimates the SEP and solar arrays would have a mass of about 9.2 mT.http://uk.wrs.yahoo.com/_ylt=A1f4cfiEU.1HOV0B.XpLBQx.;_ylu=X3oDMTE2dW5zM2pmBHNlYwNzcgRwb3MDMTIEY29sbwNpcmQEdnRpZANVSzA1MDFfNTAx/SIG=1235boedb/EXP=1206822148/**http%3A//www.entechsolar.com/SPRAT-XX-SLA-SEP.pdf
Patchouli - 29/3/2008 11:49 PMYou got a little confused I ment ISP by efficiency as for milinewtons per watt thats likely a little Really it just boils down to same energy is being put in the smaller amount of propellant making it able to do more work in producing thrust.So the new engine may use about the same amount of power but uses less propellant the achieve a given level of thrust.
Lampyridae - 31/3/2008 7:37 AMPin = solar power from your arrays, typically 100W/kg for near-term advanced photovoltaics.
meiza - 31/3/2008 7:41 PMYou need support and attitude changing structure as well as power conversion equipment for the solar cells. It's hard to get a light system. Look at ISS. The panels are very light and flexible and the trusses still mass a lot.