Author Topic: Could SLS work for a Mars Direct architecture?  (Read 11801 times)

Offline redliox

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Could SLS work for a Mars Direct architecture?
« on: 01/20/2017 12:29 AM »
Until a company like Blue Origin or SpaceX finally assemble their heavy lift vehicles, the current best option for a HLV is the SLS which is nearing completion.  Space policy aside, either the SLS 1B or 2 versions could be of great use to a Mars program.  In this case, I'm looking at the Mars Direct or Semi-Direct schemes and posing the question:

Could the SLS work for Mars Direct?

Eventually, the SLS could be phased out for a cheaper vehicle, but the future is foggy in light of the incoming administration.  However I'm not so much talking about space policy but rather whether the SLS could serve the role of the "Ares" in Zubrin's schemes.  If not I'm curious to know what is lacking, or if delivering payloads ahead to Mars could compensate while retaining a 2-3 launch scheme.
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Offline RonM

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Re: Could SLS work for a Mars Direct architecture?
« Reply #1 on: 01/20/2017 12:54 AM »
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.

Offline redliox

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Re: Could SLS work for a Mars Direct architecture?
« Reply #2 on: 01/21/2017 12:46 AM »
Well, SLS is basically what Zubrin was talking about, shuttle derived rocket tossing about 40 tonnes towards Mars.

The masses advocated for a 1B or 2 seemed in the range Zubrin wanted, and obviously SpaceX has taken this deep to heart in the ITS plans and then-some.

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.

Politics is an irritating wild card.  It's pretty much responsible for the 1980s and 90s being largely vacant of human or robotic missions with value, up until Sojourner rolled onto Mars near the end.  Like many I do hope to see SpaceX succeed but I suspect we may have to settle for something like SLS complemented by Falcon Heavys...under ideal current circumstances.
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Offline MATTBLAK

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Re: Could SLS work for a Mars Direct architecture?
« Reply #3 on: 01/21/2017 01:18 AM »
With the most feasible version of SLS that could come to pass - a Block 2 or '2b' - the traditional Mars Direct vehicles could just squeak into the SLS TMI payload figures - without getting too much into 'Rocket Lego' wishlist modifications to SLS. Make sure to tap Steve Pietrobon for his previous SLS calculations:

4x RS-25E engine corestage, 2x 5-Segment SRBs, 4x RL-10 powered Exploration Upper Stage (EUS): 39 or 40 tons direct to Trans-Mars Injection. Refer to Zubrin & Baker's documentation for M.D. vehicle mass breakdown.

SLS Feasibly & sensibly uprated: 2x 'Dark Knights' SRBs, EUS powered by higher thrust replacements for the RL-10; such as the MB-60 or Vinci engines. RS-25E uprated for higher thrust. All that would probably only boost the TMI payload to 45-47 tons - about the same as the Saturn V. Still impressive, though.

For vehicles of roughly similar capability to this - look to Blue Origin's 'New Glenn' boosters and their successors. I'd like to see Zubrin re-crunch the numbers to use a mixed-twin launch fleet of Falcon Heavy with an uprated upper stage and the most capable version of Vulcan/ACES! If Zubrin resized the Mars Direct vehicles for a crew of 3 or even only 2 Astronauts; Vulcan could launch the spacecraft and Falcon Heavy could follow the next day with an Earth Departure stage for it to rendezvous and dock with. That EDS stage could contain about 55 tons of propellants - whether that be LOX/Kerosene or LOX/CH4 - assuming the Falcon Heavy upper stage had been uprated to using a single vacuum-optimized Raptor engine. The Mars Direct vehicle could use it's own propulsion system to augment the EDS burn. Or maybe Zubrin could think outside the box and include a couple Hall thrusters and some Xenon propellant on the Mars vehicle to use as a 'cruise engine' to shape the trajectory over several days.
« Last Edit: 07/18/2017 10:10 AM by MATTBLAK »
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Offline AncientU

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Re: Could SLS work for a Mars Direct architecture?
« Reply #4 on: 01/21/2017 11:03 AM »
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.
« Last Edit: 01/21/2017 08:43 PM by AncientU »
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Offline Oli

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Re: Could SLS work for a Mars Direct architecture?
« Reply #5 on: 01/21/2017 04:59 PM »
Mars Direct falls apart once you consider a realistically sized return payload.

But regardless, any "direct" architecture is suboptimal because all launches must be concentrated within one month or so every 2 years.

For a good use of SLS I would suggest making EUS refuelable.

Offline MATTBLAK

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Re: Could SLS work for a Mars Direct architecture?
« Reply #6 on: 01/21/2017 10:46 PM »
Refueling of multi-hundred tons cryogenics in space has never been done. But get on to that asap, I say!
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Offline Darkseraph

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Re: Could SLS work for a Mars Direct architecture?
« Reply #7 on: 01/21/2017 11:00 PM »
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.



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Offline redliox

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Re: Could SLS work for a Mars Direct architecture?
« Reply #8 on: 01/21/2017 11:09 PM »
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.

Nearing isn't that loosely used.  Payloads for SLS are years into the future, but the boosters and core are being physically built and tested which is a huge step away from mere paperwork.  Also, unlike the Ares I-X test, most elements of the Block I version for the 2018 EM-1 flight are going to be identical for the IB version.  Only the upper stage, EUS, needs to be built to transition from I to IB.  The SLS is literally being made real regardless of opinion and administrations.

Unlike either Glen or ITS, the SLS isn't purely blueprints or proposal porn anymore.  It is, momentarily, THE heavy launch vehicle.  With luck, the Falcon Heavy will join this roster but more like a HLV "lite."  SLS is going to fly before any other HLV of similar or better capability.

Mars Direct falls apart once you consider a realistically sized return payload.

Not as quickly as the 1980s SEI, the 2000s Vision, or ARM.  However, any plan can be improved or modified.  Part of the process involves looking at what's currently available, and only SLS and FH will be available before 2020.

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.

Sadly that's exactly the same as for SEI, and that fell flat on its face once Congress saw the price tag.  NASA will either have to lean down or (more likely) SpaceX will indeed "win the race."
« Last Edit: 01/21/2017 11:10 PM by redliox »
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Offline Hanelyp

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Re: Could SLS work for a Mars Direct architecture?
« Reply #9 on: 01/21/2017 11:46 PM »
How few launches over how many years, and how far in the future, are they looking at for SLS these days?

Offline Oli

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Re: Could SLS work for a Mars Direct architecture?
« Reply #10 on: 01/22/2017 12:14 AM »

Not as quickly as the 1980s SEI, the 2000s Vision, or ARM.

Not sure what you mean.

However, any plan can be improved or modified. 

Yes, SpaceX has the Mars Direct (return) plan that works.

Refueling of multi-hundred tons cryogenics in space has never been done. But get on to that asap, I say!

The alternative is SEP, which is nice but a unique capability when sized for human spaceflight applications. That means a lack of competition and potentially high cost.

The other alternative is something like JPL's plan or the DRMs but they rely on SLS only.

I think bringing commercial space as well as international participation into a Mars program is crucial. EUS could be a nice departure stage, if sized properly, and refueling it would give plenty of work to commercial/internationals.

Offline Endeavour_01

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Re: Could SLS work for a Mars Direct architecture?
« Reply #11 on: 01/22/2017 01:08 AM »

Could the SLS work for Mars Direct?


Well, SLS is basically what Zubrin was talking about, shuttle derived rocket tossing about 40 tonnes towards Mars.

Zubrin himself said a few years ago that SLS was not too dissimilar from what he had in mind.




(around 8:00 mins in)

« Last Edit: 01/22/2017 01:10 AM by Endeavour_01 »
I cheer for both NASA and commercial space. For SLS, Orion, Falcon 9, Falcon Heavy, Dragon, Starliner, Cygnus and all the rest!
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Offline Dalhousie

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Re: Could SLS work for a Mars Direct architecture?
« Reply #12 on: 01/22/2017 02:20 AM »
Mars 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.

Quote
But regardless, any "direct" architecture is suboptimal because all launches must be concentrated within one month or so every 2 years.

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.

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Offline Oli

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Re: Could SLS work for a Mars Direct architecture?
« Reply #13 on: 01/22/2017 02:47 AM »
Mars 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?

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.

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).
« Last Edit: 01/22/2017 02:48 AM by Oli »

Offline Dalhousie

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Re: Could SLS work for a Mars Direct architecture?
« Reply #14 on: 01/22/2017 05:31 AM »
Mars 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
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.

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).

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.



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Offline Oli

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Re: Could SLS work for a Mars Direct architecture?
« Reply #15 on: 01/22/2017 06:21 AM »
Mars 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

That 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?

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).

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.
« Last Edit: 01/22/2017 06:22 AM by Oli »

Offline Dalhousie

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Re: Could SLS work for a Mars Direct architecture?
« Reply #16 on: 01/24/2017 07:18 AM »
Mars 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

That 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?

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).

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.

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.

« Last Edit: 01/24/2017 08:45 PM by Dalhousie »
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Online Robotbeat

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Re: Could SLS work for a Mars Direct architecture?
« Reply #17 on: 01/24/2017 07:24 PM »
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.
« Last Edit: 01/24/2017 07:25 PM by Robotbeat »
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Offline Dalhousie

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Re: Could SLS work for a Mars Direct architecture?
« Reply #19 on: 01/24/2017 08:45 PM »
Ignoring "in the last 50 years":

There is a reason for that proviso - Prior to 1965 we did not know enough about Mars to make a Mars mission resign realistic.

Quote
Werner Von Braun's original Mars Project study.

Landmark study, but is 950 launches realistic?  Nope.

Quote
Also, Zubrin's study.

The smallest Mars mission proposed by Zubrin I know of was using FH, and that was in little more than an extended email.  FH has a payload of just over 50 tonnes (I chose 50 tonnes for a reason). Link please to anything smaller. 

Quote
And Skylon's study as well.

Thanks for the link, I had not seen the paper only the promotional material, which was really making the case for Skylon, not a rational Mars mission 

It's very von Braun-esque, is it not?.   No less that 522 flights and a dedicated station to carry out the mission.  Even if you cut the mission to a third (there are three spacecraft) that is 174 flights by Skylon, plus a dedicated space station. All predicated on  Skylon of course.  Although I guess it could be argued that you could substitute Skylon with anything with similar payload.


Quote
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.

Strawman arguments.  Large launches need not be dedicated to Mars missions.  Using a hundred or more launches to assemble something is not easy, cheap or efficient. High launch rate seems like special pleading in favour of a launch provider rather than a sensible architecture.

There are good reasons why of the almost 100 Mars mission studies I have read or seen summaries of, avoid small launches.


« Last Edit: 01/24/2017 08:52 PM by Dalhousie »
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Re: Could SLS work for a Mars Direct architecture?
« Reply #20 on: 01/24/2017 08:57 PM »
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.
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Offline Dalhousie

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Re: Could SLS work for a Mars Direct architecture?
« Reply #21 on: 01/24/2017 11:47 PM »
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.

Nothing to stop independent people and groups doping these studies. There are quite a few such Mars mission studies out there.  How many advocate doing things Lego style?


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Re: Could SLS work for a Mars Direct architecture?
« Reply #22 on: 01/24/2017 11:52 PM »
So it went from "I haven't seen any" to me giving you 3 such examples to now you wanting an industry lit review to see how many there are... I hope you have a grant to fund my research on this topic! :)

...remember, even the Augustine thing suggested 40 tons was fine.
« Last Edit: 01/24/2017 11:53 PM by Robotbeat »
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Re: Could SLS work for a Mars Direct architecture?
« Reply #23 on: 01/24/2017 11:57 PM »
Also, "Lego style" is outdated. No assembly required. Just refueling and perhaps docking a few elements.
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Offline Oli

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Re: Could SLS work for a Mars Direct architecture?
« Reply #24 on: 01/25/2017 01:09 PM »
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.

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.
« Last Edit: 01/25/2017 02:03 PM by Oli »

Offline robert_d

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Re: Could SLS work for a Mars Direct architecture?
« Reply #25 on: 01/25/2017 01:35 PM »


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 could support a fairing of 8 x 5.5 meters. If Falcon Heavy works and SLS were cancelled, it might be the only option. If assembled in the VAB there might be an opportunity to launch 2 in a Martian window from 39b and along with 1 Falcon Heavy from 39A and one from Boca Chica, you could get a substantial payload ready for TLI. The 4 core could support a full sized Raptor metholox second stage.
« Last Edit: 01/25/2017 01:36 PM by robert_d »

Offline Jim

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Re: Could SLS work for a Mars Direct architecture?
« Reply #26 on: 01/25/2017 01:37 PM »

I would be interested what could be done with a Falcon "4 core".

No, that is unworkable. Just easier to build a larger diameter core.

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Re: Could SLS work for a Mars Direct architecture?
« Reply #27 on: 01/25/2017 01:40 PM »

It's much more efficient to minimise the number of launches.  Multiplying them increases the likelihood of delays. IMHO of course!


Not true.  It is more efficient to use cheaper and multiple types of vehicles and launch more often. 

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Re: Could SLS work for a Mars Direct architecture?
« Reply #28 on: 01/25/2017 02:00 PM »
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.

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.
A large fairing doesn't require a large launch vehicle. For instance, Atlas V (which is fairly skinny) has the option of a 7.1m diameter fairing in its payload guide. An upgraded Delta IV Heavy or a Vulcan Heavy should be capable of 8m if anyone ordered such a fairing.

So the questions of fairing size and payload mass can be considered separately.
« Last Edit: 01/25/2017 02:02 PM by Robotbeat »
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Offline robert_d

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Re: Could SLS work for a Mars Direct architecture?
« Reply #29 on: 01/25/2017 02:39 PM »

Not true.  It is more efficient to use cheaper and multiple types of vehicles and launch more often.

Especially if one of the vehicles has two side boosters already in production that can do a RTLS and be re-used.
:)
« Last Edit: 01/25/2017 02:40 PM by robert_d »

Offline robert_d

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Re: Could SLS work for a Mars Direct architecture?
« Reply #30 on: 01/25/2017 03:14 PM »
Anyone know what thrust an "optimized" metholox 2nd stage to SLS would have if it was able to be refueled in orbit? Would a full sized raptor be anywhere in that neighborhood.?

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Re: Could SLS work for a Mars Direct architecture?
« Reply #31 on: 01/25/2017 04:16 PM »
Try not to veer too far off topic guys; Von Braun wasn't part of either STS or SLS, and this thread is meant to see how well the SLS could be utilized for Mars Direct.  For example, assume the current administration curtails extensive SLS development and we're stuck with the SLS 1B with no immediate relief from SpaceX's ITS.  In such a situation there'd still be a 105mt HLV and several smaller vehicles (SpaceX, Launch Alliance, ect) available, each with the potential to put a combination of large and small payloads directly on Mars which was the main point of Mars Direct: to bypass orbital assembly and focus on arriving at the red planet.
« Last Edit: 01/25/2017 04:17 PM by redliox »
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Re: Could SLS work for a Mars Direct architecture?
« Reply #32 on: 01/25/2017 04:55 PM »
Then yeah, of course. Docking (like Apollo) and refueling are not traditionally considered orbital assembly, and you can do a Mars mission just with those two and EELV class vehicles. If you want to add SLS 1B, then yeah, of course you can still do it.
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Offline redliox

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Re: Could SLS work for a Mars Direct architecture?
« Reply #33 on: 01/27/2017 03:11 PM »
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 2017
SLS - due 2018 (~2023 for Block 1B)
Vulcan - due 2019
New Glen - due 2020
ITS - due 2024

While Vulcan is on the light side of usefulness for a crewed Martian mission, I thought it fair to include since it will be ULA's upcoming crew launcher - and if it's man-rated that means it could be adapted for launching applicable payloads or a crew shuttle to LEO if nothing else.

I listed each rocket with their tentative first launch (per Wikipedia).  As the SLS and it's issues between EM-1 and EM-2 reveal, the first launch and the first useful payload of a LV may be 2 different things.  There could be development issues furthermore.  All the same, it does present a timetable to refer back to and debate on.

In the world of 2025 we'll definitely have the first 3 rockets available.  My guess will be that ITS and New Glen/New Armstrong will see some delays, since both their respective companies are honestly new at giant rockets, but could be on track for Mars operations between 2027-2030.  Considering how quiet Blue Origins keeps, New Glen may have a 50/50 chance of being operational before ITS but I believe it will be the crew vehicles that dictate their schedules in the end.  Even without the much-anticipated-secret-(moreso for Blue Origins)-weapons of Space X and BO, this could be enough to seed the first surface mission.

Under the assumption we don't want to wait on commercial-HLV, if I could design the mission setup, I'd requisition 4 SLS rockets and 4 FHs.  I only favor FH because SpaceX will have a head start on Red Dragon landers before Boeing/ULA could replicate the effort.  As per Mars Semi-Direct, there'd be 3 classes of crew vehicle: Hab, Mars Ascent Vehicle, and Earth Return Vehicle.  To play it safe, a Hab plus 4 Red Dragons would arrive at Mars before even the MAV and ERV.  A second Hab would either launch with crew directly or have the crew transfer via commercial taxi (Starliner or Dragon) in LEO.
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Re: Could SLS work for a Mars Direct architecture?
« Reply #34 on: 01/27/2017 03:32 PM »
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 2017
SLS - due 2018 (~2023 for Block 1B)
Vulcan - due 2019
New Glen - due 2020
ITS - due 2024
...
I listed each rocket with their tentative first launch (per Wikipedia). 
...

First launch of ITS is NET 2020. First crewed launch NET 2022. First interplanetary crewed launch NET 2024.

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.

Offline redliox

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Re: Could SLS work for a Mars Direct architecture?
« Reply #35 on: 01/27/2017 03:45 PM »
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.

Actually it's the availability of the LV I was intentionally referring to, not whether it was capable of safely flying humans.  As an example: suppose NASA decides to go full commercial for crew vehicles but, prior to ITS or New Glen/New Armstrong, they wish to send out the base modules and cargo.  A flight tested, but only cargo ready LV, could be utilized while the final kinks of the commercial landers are worked out.  Further assuming NASA is jittery with payloads (as well as politics), that favors FH, SLS, and Vulcan for HSF hardware but no crews.

A key factor with Mars Direct was to establish a safety net for crew ahead of their mission.  Any rocket that can send better than a few tonnes to Mars is an asset.  Even if the SLS isn't matured to Block 2 before ITS arrives (in a figurative sense) 105 mt, with as much as 30 mt available for Mars, should remain a card on the table.
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Re: Could SLS work for a Mars Direct architecture?
« Reply #36 on: 01/27/2017 04:23 PM »
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.
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Re: Could SLS work for a Mars Direct architecture?
« Reply #37 on: 01/27/2017 04:42 PM »
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.
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.

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Re: Could SLS work for a Mars Direct architecture?
« Reply #38 on: 01/27/2017 05:40 PM »
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.
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.

https://mobile.twitter.com/torybruno/status/595628488410963970
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Re: Could SLS work for a Mars Direct architecture?
« Reply #39 on: 01/27/2017 06:54 PM »
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.
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.

It would be on par with FH alright.  I'm glad ULA is working to impress customers.
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Re: Could SLS work for a Mars Direct architecture?
« Reply #40 on: 01/27/2017 06:58 PM »
Oh, also New Glenn should have no problem with an 8m fairing.
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Re: Could SLS work for a Mars Direct architecture?
« Reply #41 on: 03/23/2018 11:08 AM »
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.

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.


Quote
Could 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.

http://planetary.org/blogs/casey-dreier/2018/20180322-fy18-omnibus.html

And it aparently lost Europa Clipper, so no science payloads to boost that anemic flight manifest.

So, dare I say, for all the hate against the SLS and all the (political) flaws in it - I'm quite sure it will fly, and fly pretty well, if only a little.  I'm quite confident NASA can build that rocket pretty well.

So, this said and done, why not use SLS for a Mars Direct shot or crash program, NOT to compete with Musk plan, which are for COLONIZATION, but for EXPLORATION, ahead of it ?

Let Mars-Direct-SLS be Mars' Christopher Colombus, and Musk be the Mayflower !

A case could be make that, as it stands today, SLS is good for nothing... except for Mars Direct, because as said in this thread (including by Zubrin HIMSELF) it is the exact rocket described in the Case for Mars and all the Mars Society meetings of the last 25 years !!!

The irony, the irony !
« Last Edit: 03/23/2018 11:17 AM by Archibald »
... that ackward moment when you realize that Jeff Bezos personal fortune is far above NASA annual budget... 115 billion to 18 billion...

Offline spacenut

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Re: Could SLS work for a Mars Direct architecture?
« Reply #42 on: 03/23/2018 11:58 AM »
The capability of SLS is great.  Problem is the cost.  It is just not cost effective, in comparison to new rockets coming on line.  Even existing rockets with in space assembly can get you to Mars.  Seems like if NASA were to design a Mars transfer ship, a lander, and the ability to return, then break it all down into 20 ton components (existing launchers), or even 40 ton components (FH and NG, and maybe a Vulcan heavy), Mars can be done right away.  Use existing launchers, and keep multiple manufacturers busy in various states to build the ship, (like Nautilus-X), the money would be better spent and we would already be on our way.   

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Re: Could SLS work for a Mars Direct architecture?
« Reply #43 on: 03/31/2018 07:37 AM »
Archibald - even for exploration missions a group of Falcon heavys will do the job. And a lot cheaper than SLS.

I too agree that SLS will fly and fly well. But.. (and I'm not going into US politics)

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Re: Could SLS work for a Mars Direct architecture?
« Reply #44 on: 03/31/2018 04:33 PM »
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.

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.


Quote
Could 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.

And Falcon Heavy has 4 launches on its manifest. Energia launched twice. Saturn V launched 13 times and was extremely successful arguably accomplishing more than 135 Shuttle launches or 52 Falcon launches over the last decade.

As far as Europa Clipper, this is what the 2018 Omnibus bill says:

Quote
That the National Aeronautics and
7 Space Administration shall use the Space Launch System
8 as the launch vehicles for the Jupiter Europa mission,
9 plan for an orbiter launch no later than 2022 and a lander
10 launch no later than 2024, and include in the fiscal year
11 2020 budget the 5-year funding profile necessary to
12 achieve these goals.
http://docs.house.gov/billsthisweek/20180319/BILLS-115SAHR1625-RCP115-66.pdf

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.
« Last Edit: 03/31/2018 04:33 PM by ncb1397 »

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Re: Could SLS work for a Mars Direct architecture?
« Reply #45 on: 03/31/2018 04:58 PM »
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.

Budgets can contain funding for the next year, they do not bind future budgets, and the funding can be defined differently in future.

It is at least reasonably arguable that BFS also has six launches on the manifest, from a funding source which is at least as secure.