Well, SLS is basically what Zubrin was talking about, shuttle derived rocket tossing about 40 tonnes towards Mars.
What is lacking is money and time to develop the payloads before SpaceX has their ITS system ready. Current thought based on budget reality is to start having Mars missions in the 2030s through 2040s. If SpaceX can get their act together they will beat NASA to Mars. Then again, SpaceX might not be able to pull off the funding for ITS, so NASA may still get to use SLS for Mars.Who knows what the new administration will do. They might continue funding SLS, pay SpaceX, or forget about Mars altogether.
The OP discussed SLS as 'nearing' completion* -- proposed concepts are a dozen years in the future or not even on the drawing boards.* Nearing is used loosely in the OP. Crew flight is still approximately as distant into the future as when the program was begun in 2010-11.
Mars Direct falls apart once you consider a realistically sized return payload.
Block 2 SLS would more or less work for Mars Direct. It has similar performance to the proposed Ares. For various reasons I don't know the details of, NASA has moved far away from such a lean mission architecture. Most of their proposed Mars missions are now hundreds of tons IMLEO split over half a dozen or more launches of Block 2 SLS.
Not as quickly as the 1980s SEI, the 2000s Vision, or ARM.
However, any plan can be improved or modified.
Refueling of multi-hundred tons cryogenics in space has never been done. But get on to that asap, I say!
Could the SLS work for Mars Direct?
But regardless, any "direct" architecture is suboptimal because all launches must be concentrated within one month or so every 2 years.
Quote from: Oli on 01/21/2017 04:59 pmMars Direct falls apart once you consider a realistically sized return payload.No. In the first iteration of MD the ERV was too small to be practical. In the second it was not. The second iteration featured two payloads with landed masses of 40 tonnes, equivalent to a LEO mass of 200 tonnes, well within the 300 tonne LEO capability of a ITS booster without orbital refuelling. For a similar mass you could also to a MSD mission. You could almost certainly increase the crew size by 50% and still be within the the payload of the ITS.
This is neither correct nor is sub optimal. For a series of MD or MSD missions of this size you would launch one payload to Mars for the first mission and two for every window (which could be about two months long) thereafter.
Quote from: Dalhousie on 01/22/2017 02:20 amQuote from: Oli on 01/21/2017 04:59 pmMars Direct falls apart once you consider a realistically sized return payload.No. In the first iteration of MD the ERV was too small to be practical. In the second it was not. The second iteration featured two payloads with landed masses of 40 tonnes, equivalent to a LEO mass of 200 tonnes, well within the 300 tonne LEO capability of a ITS booster without orbital refuelling. For a similar mass you could also to a MSD mission. You could almost certainly increase the crew size by 50% and still be within the the payload of the ITS.Do you have a link to this second iteration plan?
Quote from: Dalhousie on 01/22/2017 02:20 amThis is neither correct nor is sub optimal. For a series of MD or MSD missions of this size you would launch one payload to Mars for the first mission and two for every window (which could be about two months long) thereafter.Well, fact is you have to build a rocket that is much bigger than necessary (compared to LEO assembly) and is either underutilized (if it launches only twice every 2 years) or requires excessive launch infrastructure (if it, for example, launches 10 times within a window).
Quote from: Oli on 01/22/2017 02:47 amQuote from: Dalhousie on 01/22/2017 02:20 amQuote from: Oli on 01/21/2017 04:59 pmMars Direct falls apart once you consider a realistically sized return payload.No. In the first iteration of MD the ERV was too small to be practical. In the second it was not. The second iteration featured two payloads with landed masses of 40 tonnes, equivalent to a LEO mass of 200 tonnes, well within the 300 tonne LEO capability of a ITS booster without orbital refuelling. For a similar mass you could also to a MSD mission. You could almost certainly increase the crew size by 50% and still be within the the payload of the ITS.Do you have a link to this second iteration plan?It's the Zubrin and Weaver (1993) paper http://www.marssociety-europa.eu/wp-content/uploads/2011/10/Near-Term-Mars-Mission-Options_Zubrin_1993_21.pdf
Quote from: Oli on 01/22/2017 02:47 amWell, fact is you have to build a rocket that is much bigger than necessary (compared to LEO assembly) and is either underutilized (if it launches only twice every 2 years) or requires excessive launch infrastructure (if it, for example, launches 10 times within a window).It's much more efficient to minimise the number of launches. Multiplying them increases the likelihood of delays. IMHO of course!WRT to the original question you re SLS could do could MD with two SLS launches for each departing payload. That's two launches for the initial window and four launches for every window subsequently.
Well, fact is you have to build a rocket that is much bigger than necessary (compared to LEO assembly) and is either underutilized (if it launches only twice every 2 years) or requires excessive launch infrastructure (if it, for example, launches 10 times within a window).
Quote from: Dalhousie on 01/22/2017 05:31 amQuote from: Oli on 01/22/2017 02:47 amQuote from: Dalhousie on 01/22/2017 02:20 amQuote from: Oli on 01/21/2017 04:59 pmMars Direct falls apart once you consider a realistically sized return payload.No. In the first iteration of MD the ERV was too small to be practical. In the second it was not. The second iteration featured two payloads with landed masses of 40 tonnes, equivalent to a LEO mass of 200 tonnes, well within the 300 tonne LEO capability of a ITS booster without orbital refuelling. For a similar mass you could also to a MSD mission. You could almost certainly increase the crew size by 50% and still be within the the payload of the ITS.Do you have a link to this second iteration plan?It's the Zubrin and Weaver (1993) paper http://www.marssociety-europa.eu/wp-content/uploads/2011/10/Near-Term-Mars-Mission-Options_Zubrin_1993_21.pdfThat plan assumes 45t landed payload for a 72t lander. Note JPL assumed 23t payload for a 75t lander. The best I've seen from NASA is 40t payload for a 85t lander (HIAD).As for the return payload. 20t total is borderline. A good estimate for a return hab is 25t, without capsule. Orion unfueled weights ~15t, you might get away with somewhat less for a less capable design, but 5t?Quote from: Dalhousie on 01/22/2017 05:31 amQuote from: Oli on 01/22/2017 02:47 amWell, fact is you have to build a rocket that is much bigger than necessary (compared to LEO assembly) and is either underutilized (if it launches only twice every 2 years) or requires excessive launch infrastructure (if it, for example, launches 10 times within a window).It's much more efficient to minimise the number of launches. Multiplying them increases the likelihood of delays. IMHO of course!WRT to the original question you re SLS could do could MD with two SLS launches for each departing payload. That's two launches for the initial window and four launches for every window subsequently.Minimizing the number of launches is a good way to make these launches as expensive as possible. As for delays, you want to launch 4 SLS within one month? That's a lot more challenging schedule-wise than launching the same payload over the course of 2 years.
Ignoring "in the last 50 years":
Werner Von Braun's original Mars Project study.
Also, Zubrin's study.
And Skylon's study as well.
Small launchers are superior for small scale human Mars missions because you don't need a dedicated launcher. It also makes a reusable launcher more feasible because the launch rate is higher. That's what makes them superior.
Yeah, because if you work at ULA and publish such a study, you'll get a firm talking-to by your boss since ULA is part owned by Boeing. This is a real constraint. And at NASA, you HAVE to include SLS in your architecture or you won't get past internal peer review. There are major political constraints on anyone planning a smaller chunk architecture.
In your opinion. Oddly enough, I don't know of any study that supports this. Do you know of a Mars mission study in the past 50 years that has used launchers with low Earth payloads of less than 50 tonnes and shown that this is superior to using larger boosters I would be most interested in seeing it.
If you look at past Mars architectures from NASA (the DRMs), the Mars landers have always been very big. Around 100t. The advantage is you only need 2 of them. If you go with smaller but more landers, as the more recent EMC does, you don't need a 100t+ to LEO vehicle. Still, existing launch vehicles aren't enough. With HIAD landers something around 40t-50t and a ~8m fairing is probably the minimum. With mid L/D landers 60t-70t.
I would be interested what could be done with a Falcon "4 core".
It's much more efficient to minimise the number of launches. Multiplying them increases the likelihood of delays. IMHO of course!
Quote from: Dalhousie on 01/24/2017 07:18 amIn your opinion. Oddly enough, I don't know of any study that supports this. Do you know of a Mars mission study in the past 50 years that has used launchers with low Earth payloads of less than 50 tonnes and shown that this is superior to using larger boosters I would be most interested in seeing it.The disadvantages of heavy lift I see:- Very high development cost historically.- Potentially low flight rate leading to high per launch cost.- Doesn't share fixed cost with existing smaller launch vehicles.The advantages:- Bigger rockets are more efficient.- Unique capability of launching large and heavy payloads.If you look at past Mars architectures from NASA (the DRMs), the Mars landers have always been very big. Around 100t. The advantage is you only need 2 of them. If you go with smaller but more landers, as the more recent EMC does, you don't need a 100t+ to LEO vehicle. Still, existing launch vehicles aren't enough. With HIAD landers something around 40t-50t and a ~8m fairing is probably the minimum. With mid L/D landers 60t-70t.
Not true. It is more efficient to use cheaper and multiple types of vehicles and launch more often.
Looking over the time frame of the immediate future, there would be 5 chief launch vehicles worthy of consideration for a Martian mission:Falcon Heavy - due 2017SLS - due 2018 (~2023 for Block 1B)Vulcan - due 2019New Glen - due 2020ITS - due 2024...I listed each rocket with their tentative first launch (per Wikipedia). ...
If you want to compare vehicle availability, I would advise using the same date reference for each. FH won't be ready to carry crew in 2017, nor SLS ready to carry crew in 2018.
Vulcan Heavy is about 40-50 tons IMLEO. And with "distributed launch" and an 8m fairing (which it could indeed utilize) it could launch anything to the Moon that SLS can.
Quote from: Robotbeat on 01/27/2017 04:23 pmVulcan Heavy is about 40-50 tons IMLEO. And with "distributed launch" and an 8m fairing (which it could indeed utilize) it could launch anything to the Moon that SLS can.Single stick Vulcan is <40t. Currently there is no plans to build a 3 core heavy version, but G Sower did say it is an option.
Quote from: TrevorMonty on 01/27/2017 04:42 pmQuote from: Robotbeat on 01/27/2017 04:23 pmVulcan Heavy is about 40-50 tons IMLEO. And with "distributed launch" and an 8m fairing (which it could indeed utilize) it could launch anything to the Moon that SLS can.Single stick Vulcan is <40t. Currently there is no plans to build a 3 core heavy version, but G Sower did say it is an option.Tory Bruno tweeted this out. It's clearly an option, if anyone wants it.
Quote from: Dalhousie on 01/24/2017 07:18 amIn your opinion. Oddly enough, I don't know of any study that supports this. Do you know of a Mars mission study in the past 50 years that has used launchers with low Earth payloads of less than 50 tonnes and shown that this is superior to using larger boosters I would be most interested in seeing it.The disadvantages of heavy lift I see:- Very high development cost historically.- Potentially low flight rate leading to high per launch cost.- Doesn't share fixed cost with existing smaller launch vehicles.The advantages:- Bigger rockets are more efficient.- Unique capability of launching large and heavy payloads.If you look at past Mars architectures from NASA (the DRMs), the Mars landers have always been very big. Around 100t. The advantage is you only need 2 of them. If you go with smaller but more landers, as the more recent EMC does, you don't need a 100t+ to LEO vehicle. Still, existing launch vehicles aren't enough. With HIAD landers something around 40t-50t and a ~8m diameter fairing is probably the minimum. With mid L/D landers 60t-70t.
Could SLS work for a Mars Direct architecture?
Quote from: Oli on 01/25/2017 01:09 pmQuote from: Dalhousie on 01/24/2017 07:18 amIn your opinion. Oddly enough, I don't know of any study that supports this. Do you know of a Mars mission study in the past 50 years that has used launchers with low Earth payloads of less than 50 tonnes and shown that this is superior to using larger boosters I would be most interested in seeing it.The disadvantages of heavy lift I see:- Very high development cost historically.- Potentially low flight rate leading to high per launch cost.- Doesn't share fixed cost with existing smaller launch vehicles.The advantages:- Bigger rockets are more efficient.- Unique capability of launching large and heavy payloads.If you look at past Mars architectures from NASA (the DRMs), the Mars landers have always been very big. Around 100t. The advantage is you only need 2 of them. If you go with smaller but more landers, as the more recent EMC does, you don't need a 100t+ to LEO vehicle. Still, existing launch vehicles aren't enough. With HIAD landers something around 40t-50t and a ~8m diameter fairing is probably the minimum. With mid L/D landers 60t-70t.QuoteCould SLS work for a Mars Direct architecture?As a matter of fact, whatever the advantages or disadvantes of HLV, SLS seems to be unstoppable as far as Congress goes, despite the fact that so far it has exactly two missions on its flight manifest - EM-1 and EM-2. ....And it aparently lost Europa Clipper, so no science payloads to boost that anemic flight manifest.
That the National Aeronautics and7 Space Administration shall use the Space Launch System8 as the launch vehicles for the Jupiter Europa mission,9 plan for an orbiter launch no later than 2022 and a lander10 launch no later than 2024, and include in the fiscal year11 2020 budget the 5-year funding profile necessary to12 achieve these goals.
So, unless we already have crowned king Trump or NASA has completely gone off the rails, 2 Europa missions are on the manifest and as far as I can tell are 100% funded. Which means Falcon Heavy has 4 launches on the manifest and SLS has 4.
