I wonder why they went with hydrazine RCS instead of xenon. SEP RCS+CMGs is now a well-proven combination. Not enough torque for a station this size? Or not enough for control during docking?
{snip}Is there anything about that image that makes you think it's a good idea or in any way useful? It's a hot mess in the middle of nowhere. Dump the circus act for a useful LLO and the electric power and propulsion requirements evaporate, as does funding requirements.
"Near rectilinear halo orbit" is a non-starter. [...] Dump the circus act for a useful LLO and the electric power and propulsion requirements evaporate, as does funding requirements.
"Near rectilinear halo orbit" is a non-starter. If you'd like to know more about the impossibility of station keeping, manned habitation and severe constraints on every mission plan it creates, NASA has plenty of papers - oddly pointing this out and concluding we should do it anyways. Much like the terrible idea of "Lagrange Gateways" that's been floated for years, now NASA pushes an even worse idea.Cislunar Near Rectilinear Halo Orbit for Human Space Exploration - Sept 2016https://ntrs.nasa.gov/search.jsp?R=20160003078Is there anything about that image that makes you think it's a good idea or in any way useful? It's a hot mess in the middle of nowhere. Dump the circus act for a useful LLO and the electric power and propulsion requirements evaporate, as does funding requirements.
Quote from: Propylox on 07/21/2017 03:09 am{snip}Is there anything about that image that makes you think it's a good idea or in any way useful? It's a hot mess in the middle of nowhere. Dump the circus act for a useful LLO and the electric power and propulsion requirements evaporate, as does funding requirements.1. Pretty picture.2. I thought low lunar orbits (LLO) were unstable, requiring between 0-400 m/s of station keeping.Putting the DSG in LLO would make lunar landing much easier.I suspect NASA wants to put the DSG in a high lunar orbit to reduce the delta-v needed by the large mass transfer vehicle to go to Mars. However if the DSG only has a 15 year life expectancy then the Mars Transfer Vehicle (MTV) will still be under construction at the end of the Gateway's life. DSG #2 may be the return point for the MTV.
Quote from: A_M_Swallow on 07/21/2017 04:18 amQuote from: Propylox on 07/21/2017 03:09 am{snip}Is there anything about that image that makes you think it's a good idea or in any way useful? It's a hot mess in the middle of nowhere. Dump the circus act for a useful LLO and the electric power and propulsion requirements evaporate, as does funding requirements.1. Pretty picture.2. I thought low lunar orbits (LLO) were unstable, requiring between 0-400 m/s of station keeping.Putting the DSG in LLO would make lunar landing much easier.I suspect NASA wants to put the DSG in a high lunar orbit to reduce the delta-v needed by the large mass transfer vehicle to go to Mars. However if the DSG only has a 15 year life expectancy then the Mars Transfer Vehicle (MTV) will still be under construction at the end of the Gateway's life. DSG #2 may be the return point for the MTV.Has nothing to do with MTV
The other item I noticed was max weight for this co-manifested payload showing there is likely going to this orbit with Orion on a SLS-1B only 7.5mt of excess capability. Which also means that the DSG itself will have to weigh no more than 7.5mt. This orbit was probably picked because for other orbits there just was not enough excess capability to have a useful co-manifested payload.
Quote from: oldAtlas_Eguy on 07/21/2017 04:57 pmThe other item I noticed was max weight for this co-manifested payload showing there is likely going to this orbit with Orion on a SLS-1B only 7.5mt of excess capability. Which also means that the DSG itself will have to weigh no more than 7.5mt. This orbit was probably picked because for other orbits there just was not enough excess capability to have a useful co-manifested payload.Yes mass restrictions seem to be popping up and causing development problems, see links below: http://russianspaceweb.com/imp-ppb.html#2017http://russianspaceweb.com/imp-lcub.html
NASA is pushing quite an aggressive schedule, delivery in 2021 for launch in 2022 for propulsion module. Habitation module to follow the following year.
Quote from: Khadgars on 07/21/2017 05:47 pmNASA is pushing quite an aggressive schedule, delivery in 2021 for launch in 2022 for propulsion module. Habitation module to follow the following year. Can this really be done by 2021? This looks like the "hard" part of the Gateway, with the most powerful SEP system ever, no? Four years to delivery, and no contracts yet? I could believe a docking node or hab module in 4 years, if there was a lot of money, but the propulsion module seems a lot more ambitious technologically.
Quote from: jgoldader on 07/21/2017 08:40 pmQuote from: Khadgars on 07/21/2017 05:47 pmNASA is pushing quite an aggressive schedule, delivery in 2021 for launch in 2022 for propulsion module. Habitation module to follow the following year. Can this really be done by 2021? This looks like the "hard" part of the Gateway, with the most powerful SEP system ever, no? Four years to delivery, and no contracts yet? I could believe a docking node or hab module in 4 years, if there was a lot of money, but the propulsion module seems a lot more ambitious technologically.Probably helps that its almost literally the latest design of ARM without any of the grabbing equipment and an extra docking port.