For example, the Apollo TLI stage was about 320,000 pounds, placed by a single launch into a very low Earth orbit of about 90 statute miles circular, on later missions. You could have put up that many tons of mass in something like 40 Atlas launches, or 20 Titan II launches, or six to eight Saturn IB launches. So, by that logic, the Saturn V was a useless waste of money.But... each individually launched payload needs its own structure, its own avionics, its own maneuvering and attitude control system... so your one-launch TLI stage weighs 320,000 pounds, but 40 individually-launched piecework payloads will weigh on the order of half a million pounds. And can't be placed in an unstable parking orbit, because it will take weeks, if not months, to assemble them all into the piecework variant of an Apollo TLI stage, so your initial energy requirements, just to get to LEO to assemble, go up.Just comparing tonnage is like making deep space exploration into Lego elements. It woefully fails to account for an enormous host of other factors that come into play when you piece-meal an exploration stage into being from tens to hundreds of individually-launched payloads.
The only way to match SLS BLEO capabilities with smaller LV is by distributed launch, which is whole new technology to be developed and proven. Even then the EELVs in 2010 would've been to small, something in 35-50t class would be need. Commercially developed DL and 3 vehicles in this class are now in development, only 5-7yrs to late. Sent from my SM-T810 using Tapatalk
No SpaceX discussion here. SLS is the real rocket and not an impossible concept suggested by an eccentric billionaire.
The only way to match SLS BLEO capabilities with smaller LV is by distributed launch, which is whole new technology to be developed and proven. Even then the EELVs in 2010 would've been to small, something in 35-50t class would be need. Commercially developed DL and 3 vehicles in this class are now in development, only 5-7yrs to late.
So it is a race between the newly announced SpaceX BFR flight to Mars and the SLS EM-2 test flight in 2022 to see which one get off the pad first. Pass the popcorn for the forthcoming launches
Quote from: TrevorMonty on 09/28/2017 06:36 pmThe only way to match SLS BLEO capabilities with smaller LV is by distributed launch, which is whole new technology to be developed and proven. Even then the EELVs in 2010 would've been to small, something in 35-50t class would be need. Commercially developed DL and 3 vehicles in this class are now in development, only 5-7yrs to late.This is the same fallacy in another form: you identify one weakness of a non-heavy-lift approach and conclude that heavy lift is better. The fact remains that there is as yet literally no technical justification for SLS.
Quote from: Zed_Noir on 09/29/2017 06:24 amSo it is a race between the newly announced SpaceX BFR flight to Mars and the SLS EM-2 test flight in 2022 to see which one get off the pad first. Pass the popcorn for the forthcoming launchesI do in-fact believe BFR will fly, or something close to it. But I would add 10 years to the schedule, so 2032 would be first test flight of BFR IMO. For the 2020s, SLS/Orion will have plenty to do.
For the 2020s, SLS/Orion will have plenty to do.
I dunno. It's late 2017. For that statement to become true, the payload hardware needs to be in mid- to late-development now. Since Apollo, NASA human spacecraft programs (STS, ISS, Orion) have required a decade or more to design, develop, launch, and become operational.Even if DSG gets the go-ahead soon and doesn't encounter the schedule issues of those earlier programs, the emergence of ITS and similar reusable upper stages/spacecraft on an early 3030s timetable would make DSG obsolete soon after completion.{snip}
Quote from: UltraViolet9 on 09/29/2017 07:56 pmI dunno. It's late 2017. For that statement to become true, the payload hardware needs to be in mid- to late-development now. Since Apollo, NASA human spacecraft programs (STS, ISS, Orion) have required a decade or more to design, develop, launch, and become operational.Even if DSG gets the go-ahead soon and doesn't encounter the schedule issues of those earlier programs, the emergence of ITS and similar reusable upper stages/spacecraft on an early 3030s timetable would make DSG obsolete soon after completion.{snip}EM-2 is aiming for 2022. If ITS is 2030+ that give DSG 10-15 years before a rival turns up. ITS is SpaceX only where as DSG could be hosting several lunar landers from different manufacturers.
EM-2 is aiming for 2022.
If ITS is 2030+ that give DSG 10-15 years before a rival turns up.
ITS is SpaceX only where as DSG could be hosting several lunar landers from different manufacturers.
Quote from: A_M_Swallow on 09/29/2017 08:24 pmEM-2 is aiming for 2022.The DSG won't be complete and have an airlock until 2026.And that schedule holds only if the Administration and Congress approve the DSG soon.The DSG will also need to evade the kind of weak rationales, political tinkering, changing partnerships, and multiple redesigns that put Alpha/Freedom/ISS in development hell for over a decade.DSG is obviously simpler than ISS. But even if it's approved soon, based on more recent experience with our "simple" Orion, I doubt DSG can avoid similar (if not quite as long) delays as ISS and Orion.QuoteIf ITS is 2030+ that give DSG 10-15 years before a rival turns up.I don't think ITS is the only "rival". Blue Moon or an ACES lander don't need the DSG and can use multiple launchers. Even the little guys like Moon Express don't talk about DSG.I doubt ULA will pursue an ACES lander without NASA skin in the game. But Blue Origin certainly has a backer with deep enough pockets to bring Blue Moon forward in whatever timeframe he wants.{snip}