Quote from: wannamoonbase on 08/02/2022 08:37 pmQuote from: sdsds on 07/29/2022 08:08 pmQuote from: su27k on 06/24/2022 03:56 pmhttps://www.gao.gov/assets/gao-22-105212.pdfQuote from: Page 51As of February 2022, the co-manifested vehicle is above the FalconHeavy launch vehicle’s mass limit. If the mass is too high, it could affectthe vehicle’s ability to reach the correct lunar orbit. The project is takingsteps to reduce mass, including evaluating whether it needs topotentially off-load some components for initial launch.co-manifested vehicle = PPE + HALOIs there some way SpaceX can up-rate FH to meet the new mass estimate of PPE + HALO?Cutting weight in design and off loading mass before launch seems like the easiest path forward.The easiest thing to offload will be fuel, so they have a delicate balancing act to do there. Best of luck to them.
Quote from: sdsds on 07/29/2022 08:08 pmQuote from: su27k on 06/24/2022 03:56 pmhttps://www.gao.gov/assets/gao-22-105212.pdfQuote from: Page 51As of February 2022, the co-manifested vehicle is above the FalconHeavy launch vehicle’s mass limit. If the mass is too high, it could affectthe vehicle’s ability to reach the correct lunar orbit. The project is takingsteps to reduce mass, including evaluating whether it needs topotentially off-load some components for initial launch.co-manifested vehicle = PPE + HALOIs there some way SpaceX can up-rate FH to meet the new mass estimate of PPE + HALO?Cutting weight in design and off loading mass before launch seems like the easiest path forward.
Quote from: su27k on 06/24/2022 03:56 pmhttps://www.gao.gov/assets/gao-22-105212.pdfQuote from: Page 51As of February 2022, the co-manifested vehicle is above the FalconHeavy launch vehicle’s mass limit. If the mass is too high, it could affectthe vehicle’s ability to reach the correct lunar orbit. The project is takingsteps to reduce mass, including evaluating whether it needs topotentially off-load some components for initial launch.co-manifested vehicle = PPE + HALOIs there some way SpaceX can up-rate FH to meet the new mass estimate of PPE + HALO?
https://www.gao.gov/assets/gao-22-105212.pdfQuote from: Page 51As of February 2022, the co-manifested vehicle is above the FalconHeavy launch vehicle’s mass limit. If the mass is too high, it could affectthe vehicle’s ability to reach the correct lunar orbit. The project is takingsteps to reduce mass, including evaluating whether it needs topotentially off-load some components for initial launch.co-manifested vehicle = PPE + HALO
As of February 2022, the co-manifested vehicle is above the FalconHeavy launch vehicle’s mass limit. If the mass is too high, it could affectthe vehicle’s ability to reach the correct lunar orbit. The project is takingsteps to reduce mass, including evaluating whether it needs topotentially off-load some components for initial launch.
Quote from: sdsds on 07/29/2022 08:08 pmIs there some way SpaceX can up-rate FH to meet the new mass estimate of PPE + HALO?Cutting weight in design and off loading mass before launch seems like the easiest path forward.
Is there some way SpaceX can up-rate FH to meet the new mass estimate of PPE + HALO?
Is the FH currently planned to be fully expended? If not, moving to a fully expendable launch could be one option.Another possibility is to lower the target orbit, load additional Xenon for the ion engines and extend the duration of orbit raising. Might require some re-design to carry additional propellant, though.One advantage of using electric propulsion is that there can be some flexibility with the orbit insertion. It should be possible to take advantage of performance reserves by burning the upper stage to depletion, to shorten the orbit raising timeline and save PPE fuel.
Quote from: lrk on 08/03/2022 06:06 pmIs the FH currently planned to be fully expended? If not, moving to a fully expendable launch could be one option.Another possibility is to lower the target orbit, load additional Xenon for the ion engines and extend the duration of orbit raising. Might require some re-design to carry additional propellant, though.One advantage of using electric propulsion is that there can be some flexibility with the orbit insertion. It should be possible to take advantage of performance reserves by burning the upper stage to depletion, to shorten the orbit raising timeline and save PPE fuel. yesno, can't add more propellant
Quote from: lrk on 08/03/2022 06:06 pmIs the FH currently planned to be fully expended? If not, moving to a fully expendable launch could be one option.Another possibility is to lower the target orbit, load additional Xenon for the ion engines and extend the duration of orbit raising. Might require some re-design to carry additional propellant, though.One advantage of using electric propulsion is that there can be some flexibility with the orbit insertion. It should be possible to take advantage of performance reserves by burning the upper stage to depletion, to shorten the orbit raising timeline and save PPE fuel. Usually electric propulsion involves nearly continuous thrusting (which means you don’t get nearly as much of the Oberth Effect as high thrust propulsion), but if you’ve already maximized the Isp (often thrusters have an Isp range they can operate in), a thing you can do without adding more propellant is to avoid thrusting at apogee and only thrust near perigee. That gives you the advantage of the Oberth Effect, but at the expense of much more time and potentially exposure to the Van Allen belts (not a problem for human radiation limits as the Gateway stack will be uncrewed at the time, but might be a problem for electronics or the solar arrays).Electric propulsion gives you a lot of flexibility there if you’re willing to trade time.
With C3 -0.6 km2/sec2 I get a little more than 15 t .Is that about right for a TLI?
Quote from: GWR64 on 08/03/2022 05:28 pmWith C3 -0.6 km2/sec2 I get a little more than 15 t .Is that about right for a TLI?In https://www.ulalaunch.com/docs/default-source/rockets/atlas-v-and-delta-iv-technical-summary.pdfULA asserts, "TLI (Trans-lunar Injection) = C3: -2 km 2 /sec 2."
Yes, I also found different values, and had to decide.
Advance apologies for the speculation herein.In the contract awarded to SpaceX, under what fairing is PPE+HALO slated to fly? Standard size, or the extra big one being developed for another customer?In either case, is there room inside for additional hardware?Finally, under what circumstances (if any) would addition of a solid motor, sort of like a stage 3, improve the effective performance of FH?
somehow cramming an extra COPV full of xenon into HALO might work
The downside to this type of thruster is that the insulator is eroded during operation [and] the erosion of the propellant channel is the main lifetime limitator of this type of thruster,
Quote from: DanClemmensen on 08/07/2022 11:40 pmsomehow cramming an extra COPV full of xenon into HALO might workThat's very creative! And yes, it might work. But see:https://beyondnerva.com/electric-propulsion/hall-effect-thrusters/and in particular:QuoteThe downside to this type of thruster is that the insulator is eroded during operation [and] the erosion of the propellant channel is the main lifetime limitator of this type of thruster, So in a slow spiral out to the destination orbit some percentage of the useful life of the thruster is consumed.
Quote from: DanClemmensen on 08/07/2022 11:40 pmsomehow cramming an extra COPV full of xenon into HALO might workThat's very creative! And yes, it might work. But see:https://beyondnerva.com/electric-propulsion/hall-effect-thrusters/
Here's an image GAO says comes from the contractors, showing the co-manifested payload under the fairing. Since PPE is on top, couldn't they squeeze a STAR-48V motor into the upper conical section of the fairing?NASA (in LSP-PLN-324.01 Revision C) specifically allows, "final stages (exclusively used for orbit circularization or escape)" to be added to a LV, without requiring recertification.