"That architecture looks immensely complicated and high risk."It does, and frankly the SpaceX version is also troublingly complex and high risk, it seems to me. How it makes one long for Apollo's one-shot approach. What Apollo couldn't (or rather didn't) do was to pre-land equipment and supplies, which could be done now with the larger CLPS landers. It would be really good to see a plan using one of our big sparkly new launchers to fly a one-shot mission augmented with pre-landed payloads.
Quote from: Hug on 03/05/2023 11:17 pmQuote from: TheRadicalModerate on 03/05/2023 08:58 pmWhat the hell is Boeing doing on National Team Mark II?Quotelarger tanks using a new manufacturing technique...Now large hydrolox composite tanks is something Boeing has a fair bit of experience with and is something Blue presumably needs...OK, but why are they are singled out as being part of the "team", and not just being a contractor?I would imagine that everyone on the team is sharing the risk of the program (and any reward), but if you are a contractor then you get paid for whatever you do, regardless if the end result is successful or not.Not sure we still understand...
Quote from: TheRadicalModerate on 03/05/2023 08:58 pmWhat the hell is Boeing doing on National Team Mark II?Quotelarger tanks using a new manufacturing technique...Now large hydrolox composite tanks is something Boeing has a fair bit of experience with and is something Blue presumably needs...
What the hell is Boeing doing on National Team Mark II?
larger tanks using a new manufacturing technique
Quote from: Phil Stooke on 03/06/2023 05:49 pm"That architecture looks immensely complicated and high risk."It does, and frankly the SpaceX version is also troublingly complex and high risk, it seems to me. How it makes one long for Apollo's one-shot approach. What Apollo couldn't (or rather didn't) do was to pre-land equipment and supplies, which could be done now with the larger CLPS landers. It would be really good to see a plan using one of our big sparkly new launchers to fly a one-shot mission augmented with pre-landed payloads.By definition, any HLS architecture with even one reusable component requires refueling in NRHO. That's an irreducible minimum of complexity.The real question is whether there's something that has to happen in LEO that can cause the whole mission to fail. As a practical matter, the NRHO refueling tanker has to be loaded via one or more refuelings in LEO.Note that SpaceX is not an exception here. In sustaining operations, lift tankers will refuel a depot in LEO, and then either one lift tanker or the depot itself will fly to NRHO to refuel the LSS.Tankers have cheap payloads--propellant. So the real risk is losing one during launch or during RPOD with the depot or the tanker that's going on to NRHO. If you have cheap launch and high cadence, that risk in LEO is minimal. If you lose one, you just launch another. On the other hand, if launchers are expensive or have low cadence, loss of a tanker is a big deal.I worry more about low cadence for any non-Starship CLV than I do about cost. The risk of a failed launch is easy to actuarially average into the bid for the SLD/SLT service. But if low cadence following a failure makes the prop already in LEO boil away, that's a problem.
Dynetics will use Vulcan to deliver fuel directly to NRHO so no LEO operations required. Long term storage of fuel at NRHO is requirements as they need multiple fuel launches. The delays from losing one shouldn't be problem.
Quote from: TrevorMonty on 03/07/2023 07:45 pmDynetics will use Vulcan to deliver fuel directly to NRHO so no LEO operations required. Long term storage of fuel at NRHO is requirements as they need multiple fuel launches. The delays from losing one shouldn't be problem.But that means that you have to risk your expensive reusable vehicle doing multiple risky RPODs in NRHO, where any mishap is a loss of mission, as opposed to doing one risky RPOD in NRHO and multiple low-stakes ones in LEO.I think Dynetics has decided that this trade is worth it, because they're probably going to be using drop tanks. But they've also decided on a single DAE architecture that does NRHO-LS-NRHO all by itself (albeit losing the drop tanks a bit before landing). Even with the drop tanks, though, the crew module that can be landed and returned to NRHO is extremely small for a crew of 4 for 5 days--much smaller than Nat Team could deliver for the same number of VC6 launches.This is why I still think that Dynetics' best bet is to plan to use Starship to deliver prop, but size all of the delivery tanks so multiple tanks can be stacked in the Starship payload bay, or individual ones can be launched on a VC6. If Starship works, they're golden. If Starship fails completely, they're toast. But they're also toast if their crew module is so small that NASA doubts it can fulfill the requirements.
If Dynetics aren't designing to meet NASA requirements then they are in wrong business.
But that means that you have to risk your expensive reusable vehicle doing multiple risky RPODs in NRHO, where any mishap is a loss of mission, as opposed to doing one risky RPOD in NRHO and multiple low-stakes ones in LEO.I think Dynetics has decided that this trade is worth it, because they're probably going to be using drop tanks
Quote from: TheRadicalModerate on 03/07/2023 11:54 pmBut that means that you have to risk your expensive reusable vehicle doing multiple risky RPODs in NRHO, where any mishap is a loss of mission, as opposed to doing one risky RPOD in NRHO and multiple low-stakes ones in LEO.I think Dynetics has decided that this trade is worth it, because they're probably going to be using drop tanksOk so at a baseline, it's 4 or 5 (youtu.be/RUchpnV2Uq0?t=1424) launches of Vulcan + the associated propellant spacecraft to deliver the 40 tons (youtu.be/RUchpnV2Uq0?t=1817) of methane liquid oxygen propellant. Droptanks got dropped in August 2020 (which is why they had issues with the mass margins; they didn't have time to mature the design). The whole 4/5 RPOD with Alpaca is presumably part of the reason why Dynetics want the NRHO depot (+presumably reducing boiloff to help with launch timeframes). Starship gets ~4 launches to do same. That's because you have to move all that Starship dry mass; it's better at scale, delivering 200 tons only requires 8 launches (so it would like a depot as well).
Quote from: Hug on 03/08/2023 05:15 amQuote from: TheRadicalModerate on 03/07/2023 11:54 pmBut that means that you have to risk your expensive reusable vehicle doing multiple risky RPODs in NRHO, where any mishap is a loss of mission, as opposed to doing one risky RPOD in NRHO and multiple low-stakes ones in LEO.I think Dynetics has decided that this trade is worth it, because they're probably going to be using drop tanksOk so at a baseline, it's 4 or 5 (youtu.be/RUchpnV2Uq0?t=1424) launches of Vulcan + the associated propellant spacecraft to deliver the 40 tons (youtu.be/RUchpnV2Uq0?t=1817) of methane liquid oxygen propellant. Droptanks got dropped in August 2020 (which is why they had issues with the mass margins; they didn't have time to mature the design). The whole 4/5 RPOD with Alpaca is presumably part of the reason why Dynetics want the NRHO depot (+presumably reducing boiloff to help with launch timeframes). Starship gets ~4 launches to do same. That's because you have to move all that Starship dry mass; it's better at scale, delivering 200 tons only requires 8 launches (so it would like a depot as well).I didn't know they'd lost the drop tanks. Kinda too bad, but it does indeed lower complexity.With no drop tanks, and 4 VC6 tanker launches, the crew module gets really small. I get something like 4.4t, which will be pretty cozy for a crew of 4 and a mission duration of 5 days. (I'm doing the mission duration from memory; is that right for the SLD specs?)
I thought 4 crew capacity was more for ferrying them back fore to habitat.
Quote from: TrevorMonty on 03/08/2023 11:31 pmI thought 4 crew capacity was more for ferrying them back fore to habitat.You're looking for Attachment A01 from Appendix P.
Quote from: TheRadicalModerate on 03/09/2023 04:37 amQuote from: TrevorMonty on 03/08/2023 11:31 pmI thought 4 crew capacity was more for ferrying them back fore to habitat.You're looking for Attachment A01 from Appendix P. Still ferrying crew just allows few days for it. Is that 5days the typical time in lander or worst case scenerio.