Heavy lift is settled –by Mike Griffin- as the “Big Picture”. Ares is just a “tool” used in that big picture and we believe it is the wrong tool. So we proposed another “tool”; DIRECT.
meiza - 29/12/2007 4:36 PMQuoteHeavy lift is settled –by Mike Griffin- as the “Big Picture”. Ares is just a “tool” used in that big picture and we believe it is the wrong tool. So we proposed another “tool”; DIRECT.It's telling that you don't consider the moon the goal and heavy lift just a tool. No, heavy lift is a goal in itself for you.
Nathan - 29/12/2007 6:02 PMThere is no real reason that the EELV-L1 architecture, based on an L1 propellant depot won't work. Is there?
Nathan - 29/12/2007 7:02 PMOkay folk - lets assume that either th SpaceX COTS vehicle Dragon will be available for the Command module and that this command module can connect to a reuselable Earth departure stage.Other options for the command module include Interorbital systems CM-1 or a clean sheet design. Also assume that NASA decides to go the EELV route, regardless of one's opinion on that, so that NASA is an eager customer.There is no real reason that the EELV-L1 architecture, based on an L1 propellant depot won't work. Is there? (indeed, LOR-LOR will also work).
kraisee - 29/12/2007 11:31 PM I'm not sure who else has been able to crunch any numbers on this, but I'm not getting great performance from the L1 Depot architecture. I'm getting better results from an LOR Depot architecture because fewer Centaur Stage have to be pushed through TLI. It results in greater mass in Lunar Orbit in the end. It should also be noted that I'm not talking about a 23mT CEV, nor a 45mT LSAM - I'm talking about , at best, a 40-42mT of combined CEV and LSAM - which would result in a lander more closely resembling Apollo's 2-person one than ESAS'. Ross.
clongton - 29/12/2007 11:33 PMQuoteNathan - 29/12/2007 7:02 PMOkay folk - lets assume that either th SpaceX COTS vehicle Dragon will be available for the Command module and that this command module can connect to a reuselable Earth departure stage.Other options for the command module include Interorbital systems CM-1 or a clean sheet design. Also assume that NASA decides to go the EELV route, regardless of one's opinion on that, so that NASA is an eager customer.There is no real reason that the EELV-L1 architecture, based on an L1 propellant depot won't work. Is there? (indeed, LOR-LOR will also work).If we're going to assume that everything NASA has done to date has been thrown out, I think that would also include Orion "as designed". It was deliberately made too big for the Atlas in the first place so I think the first thing to do is to redesign it and create a spacecraft that the Atlas can fly. Begin by redesigning the Orion. This time the CM should be just a taxi, and not include "living space". It should be a 3-module spacecraft, similar to Soyuz, with a mission module and a properly designed SM. SM and MM are expendable, CM is reusable. And don't worry about carrying enough LOX in the SM to get to the moon at launch time, just the LH2 with enough LOX for initial maneuvering to the depot. Fill up in LEO at the depot before departing. For LEO missions, the SM is fully fueled with its LH2 and LOX and the MM is launched with the CSM and the whole stack shouldn't exceed 18mT. For lunar missions, the SM would be lunar sized (larger) with only a partial LOX load and the LSAM is the MM and would be launched separately, with LOX propellant tank empty. They would all meet up at the depot, fill up and go.Just a note. The depot is a LOX depot. The LH2 required for the mission is very light and would be carried up at launch time in both the SM and the LSAM. That way we don't worry about boiloff issues for the LH2.
Marsman - 30/12/2007 12:45 PMWhat are you assuming?
tnphysics - 30/12/2007 3:15 PMI assume that all expensive systems (life support, guidance, etc.) would be in the reusable CM.
kraisee - 30/12/2007 4:36 PMChuck,Its an interesting idea, but I have absolutely no idea how to accurately calculate the mass breakouts for that, so somebody else is going to have to work that out.Another idea entirely... Perhaps this is all wrong. Perhaps we need a different approach entirely. Think N**lear Lightbulb powered reusable LEO>LLO taxi module. Always refuelled in LEO. Crew Module is the *only* thing launched with crew (on something like an Atlas 401 perhaps?), and the only thing disposed of is the lander (early generation architecture), but even it is replaced ultimately with a reusable unit.Yes, there is a considerable cost for development of the Prometheus tech, but it does simplify things massively overall with the limited lift capacity.Prometheus Module performs TLI, MMC, Plane Change & LOI. Then loiters in LLO for the duration of the mission. Lander undocks, descends, performs surface mission then later ascends & docks. Prometheus then performs Plane Change, TEI, MCC and EOI and loiters in 220nm LEO for the next mission. CM undocks and crew immediately re-enters.Next mission starts by launching new lander to Prometheus Module, then using Centaur-style stages to perform automated dockings to refuel both Prometheus and Lander with suitable propellant. They use the same docking adapter as the CM ultimately will."Life Support" (a la Apollo 13) for Crew is provided by LSAM habitat.This basic approach scales up to Mars quite nicely too IMHO.Ross.
clongton - 30/12/2007 5:32 PMOh RossYou're pushing ALL my buttons at once!I had this conversation with vanilla on another thread, and we used a NERVA-style engine for the spacecraft's propulsion.Basically though, we flew Orion to and from HEO, not LEO, because everyone who participated in the conversation said too many people would be nervous about a nuclear engine approaching the earth after the TEI burn.
meiza - 30/12/2007 6:27 PMnukes could be useful for Mars, not the moon.
kraisee - 30/12/2007 6:24 PMI don't have the same fear. I'm more concerned about suns radiation effects in HEO. Approaching Earth you're always in a Hohmann Transfer orbit - a highly elliptical one of course, but the low-point of the orbit (periapsis) would never be targeted below 200-400nm LEO. A non-catastrophic engine failure would leave the spacecraft in a highly elliptical orbit.If the engine were to fail spectacularly, you will still never end up lower than that. The worst-case scenario is some fragments of an exploded engine might degrade down towards the atmosphere, but they are going to have to re-enter without protection. I wouldn't expect anything to reach the surface.
But I would personally want such an engine to be built to a much higher safety margin than normal engines. If normal hardware has a 1.4 safety factor, then this thing needs to be 2.0 or better - and designed to handle catastrophic failure in a fashion, which does not risk the atmosphere.As for making the lander go all the way from Earth to the Lunar Surface - I don't think that’s workable myself because it makes the Lander awfully big and heavy carrying all that propellant. It also offers zero lifeboat capability during transit, so I don't think its the right approach myself.Ross.
meiza - 30/12/2007 7:35 PM"It cannot explode"So how about a failure causing a temperature excursion and core disintegration sending a big portion of the core to free space?