Author Topic: Human Space Exploration Architecture Using Commercial Launch/Propellant Depots  (Read 135022 times)

Offline mmeijeri

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All very interesting, but we're getting waaaay off-topic.
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Offline Robotbeat

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It was one of these Project Troy talks that alerted me to cyanogen as a possible Martian ISRU fuel. I really like Project Troy, it seems like a nice, new spin on things, getting away from the NASA perspective and the Zubrin perspective a little bit.
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Offline HappyMartian

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It was one of these Project Troy talks that alerted me to cyanogen as a possible Martian ISRU fuel. I really like Project Troy, it seems like a nice, new spin on things, getting away from the NASA perspective and the Zubrin perspective a little bit.


After building ice hydrolox ISRU facilities on the Moon, suddenly are we going to spend a whole lot of money to develop a new technology for a lower performing propellant combination ISRU facility and some new and fashionable rocket engines for exploring Mars?

Why? Because it sounds cool? 

Does each planet and moon and asteroid in our Solar System need its own nifty and cool specific propellant combination for unique rocket engines and lander designs that are less efficient than hydrolox based Landers?

High efficiency liquid hydrogen propellant is needed for VASIMR engines and other ion rocket engines.

High efficiency liquid hydrogen propellant is needed for nuclear thermal rocket engines.

We know how to build high efficiency hydrolox rocket engines.

Continually spending money on reinventing the wheel or sailboat isn't a very efficient way to explore, if exploring is what we really want to do.

Do some folks have a phobia about liquid hydrogen?

Do some folks think that space exploration should be as expensive a technology exercise as we can make it?

Or should we focus on living off the land and not 'fixing' things that are already working extremely well?

Without demonstrating that we space cadets are wise and careful stewards of the money from taxpayers and business investors there isn't much of a reason to expect consistent financial support for exploring and colonizing our Solar System, is there?


Cheers! 
"The Moon is the most accessible destination for realizing commercial, exploration and scientific objectives beyond low Earth orbit." - LEAG

Offline Robotbeat

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Who says we're going to build ice ISRU plants on the Moon? Sounds complicated.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline joek

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Does each planet and moon and asteroid in our Solar System need its own nifty and cool specific propellant combination for unique rocket engines and lander designs that are less efficient than hydrolox based Landers?

Interesting question.  What's the optimal general purpose propellant?  Or maybe, what's the optimal general purpose engine?  Or, what's the optimal general purpose propellant-engine combination?

E.g., within the scope of exploration X, there are available propellants Y, which may be consumed by engines of type Z... Consider X as a given (your choice); Y may be dependent on a number of factors, such as transportation costs, depots, ISRU, ...; Z may be dependent on engine type or the ability of the engine to use different propellants.*

Heckuva optimization problem.


* edit: propellants not fuel.  Which also brings to mind that, e.g., shipping ISRU production of raw or intermediate feedstock is not necessarily preferred to ISRU production of final product (usable propellant); shipping raw or intermediate feedstock vs. final product (usable propellant) is yet another optimization problem.
« Last Edit: 10/14/2012 03:25 am by joek »

Offline Robotbeat

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Well, we don't drive around in liquid hydrogen and liquid oxygen cars, do we? No, we use air and petroleum-based fuel because it is cheaper to use what is easily available. On Mars, that is stuff made out of carbon dioxide (and maybe nitrogen) because it is available on every single spot on the planet in unlimited amounts using the simplest of extraction techniques.
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Offline HappyMartian

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Well, we don't drive around in liquid hydrogen and liquid oxygen cars, do we? No, we use air and petroleum-based fuel because it is cheaper to use what is easily available. On Mars, that is stuff made out of carbon dioxide (and maybe nitrogen) because it is available on every single spot on the planet in unlimited amounts using the simplest of extraction techniques.



Last time I checked we usually had to drill for oil on Earth, then sometimes transport it in ships to a refinery which was sometimes very far away, and then transport it to gas stations. Using ISRU produced hydrolox for reusable Landers on the Moon, Phobos, Mars and Ceres might be more than a bit cheaper than trying to develop the technology, transportation systems, and rocket engines that use lower ISP methane and various other hip propellants.

And as many folks have noted previously, we need liquid hydrogen for VASIMR engines and for nuclear thermal rocket engines. Developing additional separate propellants with lower ISPs and new ISRU technologies and new rocket engines that are optimized for every location in the Solar System does not seem to be a very efficient way to spend money. Hydrolox is highly efficient and we have many decades of valuable experience in using it in rocket engines.

We can build high efficiency hydrolox rocket engines and do ISRU on the Moon, Phobos, Mars, and Ceres to enable robust and affordable exploration missions with reusable spaceships using liquid hydrogen or hydrolox rocket engines or we can spend scarce tax dollars for using a Human Space Exploration Architecture that Uses Commercial Launch/Propellant Depots shipped into orbit by expensive throwaway spaceships launched from the Earth. 

We have choices. Until someone can show a lower cost space architecture, it seems likely that Congress and Presidents who are serious about cislunar transportation and commercialization needs will continue to focus on using the Moon, ISRU, and hydrolox as the keys to America's future in space exploration.

The empty L2, unknown asteroid, Mars, and methane political hype should be seen for what it is.

The paper that is the basis of this thread,
 
Evolved Human Space Exploration Architecture Using Commercial Launch/Propellant Depots By Dr. Alan Wilhite, Dr. Dale Arney, Christopher Jones, and Patrick Chai
At: http://www.newspacewatch.com/docs/IAC-12.D3.2.3.x15379-NASAStudy.pdf

notes the following:

"Based on current budget projections for NASA, a flat
line budget of $3B to $4B seems to be more realistic.
Even with the commercial launch/propellant depot
having 32 percent less cost, either the Near-Earth
Asteroid program needs to be scaled back or a less
aggressive program like lunar science and in-situ
resource development may be a better choice
."

I added the bold.



Or:

NASA Reveals Goal for Eventual Manned Lunar Outpost 
BY Andy Pasztor   September 13, 2012
At: http://online.wsj.com/article/SB10000872396390444017504577648481492479016.html

"The Obama administration has laid out its most detailed ambitions yet for a return of U.S. astronauts to the moon, including the prospects of a lunar outpost where explorers could live for months at a time."

And, "Lori Garver, the No. 2 NASA official, on Tuesday gave a speech in which she emphasized the importance of exploring the moon and its environs. She also disclosed that an unspecified mission to the moon is tentatively scheduled as early as 2017."



See also:
Reality Trumps Politics On Space Policy Debate By Frank Morring, Jr. October 08, 2012
At: http://www.aviationweek.com/Article.aspx?id=/article-xml/AW_10_08_2012_p50-500383.xml


Cheers!


Edited.
« Last Edit: 10/14/2012 07:24 am by HappyMartian »
"The Moon is the most accessible destination for realizing commercial, exploration and scientific objectives beyond low Earth orbit." - LEAG

Offline mmeijeri

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And as many folks have noted previously, we need liquid hydrogen for VASIMR engines and for nuclear thermal rocket engines.

No we don't. VASIMR and NTR can work with many propellants. In addition it is not a given that VASIMR can be made to work at all (depends on the feasibility of that magical power source) or that NTR will be practically useful.
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Offline KelvinZero

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We have choices. Until someone can show a lower cost space architecture, it seems likely that Congress and Presidents who are serious about cislunar transportation and commercialization needs will continue to focus on using the Moon, ISRU, and hydrolox as the keys to America's future in space exploration.
Rather this suggests to me that we should be doing tech development to investigate a lower cost space architecture, especially one based on commercial launchers.

H2/O2 may well prove the best propellent, but it is extremely painful to watch these extremely expensive launcher decisions being locked in before investigating propellent depots and actually sending something to the lunar poles, as we would have had if congress had not slaughtered Obama's tech-centric plan.

Offline peter-b

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Hydrogen is a pretty rubbish propellant, really. It's incredibly difficult to store and its very bulky.
Research Scientist (Sensors), Sharp Laboratories of Europe, UK

Offline Robotbeat

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regardless all these guys use liquid oxygen for oxidizer and that usually carries the bulk of the mass, especially for hydrogen
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Offline JohnFornaro

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Hydrogen is a pretty rubbish propellant, really. It's incredibly difficult to store and its very bulky.

Well, why do they use it so much, then?
Sometimes I just flat out don't get it.

Offline mmeijeri

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Rubbish for spacecraft maybe, though even that may not necessarily be true forever.
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Offline HappyMartian

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And as many folks have noted previously, we need liquid hydrogen for VASIMR engines and for nuclear thermal rocket engines.

No we don't. VASIMR and NTR can work with many propellants. In addition it is not a given that VASIMR can be made to work at all (depends on the feasibility of that magical power source) or that NTR will be practically useful.

Sure. Many propellants can work with VASIMR and NTR, but which propellant works the best with chemical rockets, VASIMR, and NTR? Highly efficient hydrolox is what we know works best for launchers with upper stages that power fast human spaceflights through the Earth's radiation belts.

Every extra kilogram of required propellant for a spacecraft on the Lunar surface adds 500 kilograms to the launcher on Earth. Launchers on Earth are expensive. Drive launch costs up high enough and you won't have many human spaceflight missions to the Lunar surface or to beyond cislunar space.

A space cadet's 'favorite propellant' is not the issue. Cost is the issue. If I may quibble a bit about  what the authors of the paper that is the basis of this thread noted:

Evolved Human Space Exploration Architecture Using Commercial Launch/Propellant Depots By Dr. Alan Wilhite, Dr. Dale Arney, Christopher Jones, and Patrick Chai
At: http://www.newspacewatch.com/docs/IAC-12.D3.2.3.x15379-NASAStudy.pdf

"Based on current budget projections for NASA, a flat
line budget of $3B to $4B seems to be more realistic.
Even with the commercial launch/propellant depot
having 32 percent less cost, either the Near-Earth
Asteroid program needs to be scaled back or a less
aggressive program like lunar science and in-situ
resource development may be a better choice."


Perhaps their wording should have been something like this:

'Even with the commercial launch/propellant depot
having 32 percent less cost, either the Near-Earth
Asteroid program needs to be scaled back or a more efficient and
aggressive program like lunar science and in-situ
resource development may be a better choice.'


Could we have the cost savings of robot ice mining, a robot built modular ISRU hydrolox production facility, and the convenience of hydrolox 'gas stations' in the polar regions of the Moon? 

Why not?

Could we supply propellant to reusable Lunar Landers that are permanently based near the polar ice ISRU hydrolox production facility?

Could Lunar based Landers meet arriving Orion spacecraft in a Lunar polar orbit and take the crew down to the polar ISRU hydrolox base?

If so, then why build a propellant depot in low earth orbit, unless it is going to be filled by VASIMR powered zero boil off tankers arriving from a Lunar polar obit?

Could such VASIMR powered zero boil off tankers simply meet the LEO spacecraft that needs the hydrolox and do a 'buddy transfer' of the propellant and thus eliminate the need for a low Earth orbiting propellant depot? 

And why should an Orion spacecraft take a detour route to an L2 space station and then back to the Moon and expose its crew to many more days of radiation and risk than would be the case with a direct Apollo style flightpath to the Moon?

Oh I think I finally get it. If we build an out of the way expensive L2 space station and have a Lunar Lander that uses methane as a propellant, then we could have unduly long and risky flights to the Moon and the President could proudly claim we are preparing to do missions to an unknown asteroid and Mars. The L2 station is a bad idea. Robust Moon, asteroid, Mars, and Ceres missions will need ISRU hydrolox propellant production facilities on the Moon, Phobos, Mars, and Ceres.

Any future long distance human spaceflight exploration missions could be assembled and have ISRU hydrolox propellant provided by zero boil off hydrolox tankers in a high Lunar orbit or a high Earth orbit or an L2 orbit.   

Welcome to the low cost ISRU space exploration paradigm that will enable far more science to be done across the surface of the Moon, Mars, and Ceres through repeated hop sortie missions with reusable Landers based at ISRU hydrolox facilities than would be the situation with the expensive, old, massive, and extremely science limited on site surface missions that use the low efficiency store-able propellant plans some folks have been trying to sell for decades.     

And you know mmeijeri, I am a fan of affordable Moon, Mars, and Ceres human spaceflight missions and expect this low cost ISRU hydrolox paradigm will actually greatly multiply the exploration science that can be accomplished at distant destinations.

The efficient and extensive production of scientific knowledge on the Moon, Mars, and Ceres is quite important because such information is an easily exportable product across the Solar System and provides an initial and clear justification of why we humans and our robots are exploring space.

It is the ISRU production of hydrolox on the Moon that is our game changer that gains us valuable experience with reusable Lunar hydrolox Landers, tanker spacecraft and puts an end to expensive new missions by Earth based throwaway commercial tanker launchers, an unneeded and risk adding L2 space station, and perhaps even the need for a low Earth orbiting hydrolox depot space station.

 
Cheers!


Edited.
« Last Edit: 10/17/2012 11:18 am by HappyMartian »
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Offline pathfinder_01

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Hydrogen is a pretty rubbish propellant, really. It's incredibly difficult to store and its very bulky.

Well, why do they use it so much, then?

It has the highest possible ISP of any practical propellant in use(there are some more higher ISP ones but the propellants are even harder to handle).

The advantage is that a chemical stage using loh/lox can be mass less than one using other propellants but this comes at a cost.

Basically LOH requires bulkier tanks and more insulation which increases dry mass and volume. It is hard to store(boil off and metal embritilment) which makes it less attractive for any system that is planning on reuse. It also gives less thrust than some other combos(and in a 1st stage thrust is really important.).

These combine to make for big problems. For instance Apollo only had a few hours to decided to go or not go to the moon due to boil off. Not a huge problem as the crew and all equipment would travel on the Saturn V, but it does make prepositioning in LEO more complicated.

Cxp would have required developing some sort of insulting blanket to keep it's propellant from boiling off and even worse required 2 rockets be launched within 48 hours of each other(i.e. if the Ares-1 had a little problem and needed to roll back the whole lunar mission would be scraped...talk about launch pressure!).


In terms of lunar lander design, it would make your lander mass a bit less(but not that much less) but you have bigger bulkier tanks to deal with(i.e. crew cabin much higher from the ground) and LOH has never been kept in space as long as required for a trip to the moon(i.e. technical risk).  And the embrilment is not a good thing for the tanks, pipe or engine.  The boil off issuse could also greatly limit how long your lunar lander can stay on the moon and have enough propellant to return.

Basically it is a great propellant for an 2nd stage or an upper stage and a dealable propellant for a first stage. But in terms of manned exploration it puts some rather large requirments on it.

Anyway the effect of the increase in dry mass is that a system using loh/lox is not quite as efficent as you would expect just from the ISP. The density of other propellants means smaller tanks as well as less insulation(if any) such that basically loh/lox is not allways the best propellant choice for any particular application.
« Last Edit: 10/15/2012 04:07 pm by pathfinder_01 »

Offline mmeijeri

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Sure. Many propellants can work with VASIMR and NTR, but which propellant works the best with chemical rockets, VASIMR, and NTR? Highly efficient hydrolox is what we know works best for launchers with upper stages that power fast human spaceflights through the Earth's radiation belts.

You are confusing highest Isp with best and ignoring the difficulty of getting from where we are to a LOX/LH2 intensive transportation system. And I have always said LOX/LH2 was best for LEO to L1/L2.

Quote
Drive launch costs up high enough and you won't have many human spaceflight missions to the Lunar surface or to beyond cislunar space.

Drive tonnage up high enough and launch prices will drop dramatically, which is what will open up space. High Isp in-space propulsion is still important after that, but by itself it won't open up space. And note that even the big improvement in Isp for in-space propulsion will come from electric propulsion, not use of LH2.

Quote
A space cadet's 'favorite propellant' is not the issue. Cost is the issue.

Of course, and yet you seem overly fascinated by LOX/LH2. It will make hardly any difference to IMLEO initially, and commercially available launch prices are what really counts.

Quote
And why should an Orion spacecraft take a detour route to an L2 space station and then back to the Moon and expose its crew to many more days of radiation and risk than would be the case with a direct Apollo style flightpath to the Moon?

Not many more days, one or two more days, and there would be no great increase in radiation risk. I thought we'd been through this before. A crew capsule (not necessarily Orion, it could be Dragon or CST-100 too) would need a storm shelter against SPEs anyway and for the short durations involved GCR is not an issue.

Quote
If we build an out of the way expensive L2 space station

Not out of the way, right on the way to the moon. Also not expensive, but cheaper than a moon base.

Quote
And you know mmeijeri, I am a fan of affordable Moon, Mars, and Ceres human spaceflight missions and expect this low cost ISRU hydrolox paradigm will actually greatly multiply the exploration science that can be accomplished at distant destinations.

As far as I can tell no one here is arguing against the use of LOX/LH2, and I know I have energetically advocated its use for segments where it makes sense, and at the time it makes sense. The argument is over how to best get there, and against dogmatically insisting we need to start using LOX/LH2 for everything straight away.

Quote
The efficient and extensive production of scientific knowledge on the Moon, Mars, and Ceres is quite important because such information is an easily exportable product across the Solar System and provides an initial and clear justification of why we humans and our robots are exploring space.

No one has argued otherwise, and many have advocated it.
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Offline pathfinder_01

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 High Isp in-space propulsion is still important after that, but by itself it won't open up space. And note that even the big improvement in Isp for in-space propulsion will come from electric propulsion, not use of LH2.


And even then for electric propulsion, basically thrust and ISP are sorta opposites. In theory Hydrogen gives the best possible ISP to electric propulsion. The reality is that ISP has to take a back seat to Practicality. Hydrogen yields much less thrust and so converts a mission using electric propulsion form on that could take months to one that would take years. It just isn't a good propellant choice for electric propulsion at all.

Offline oldAtlas_Eguy

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The most disturbing item of the paper is Figure 11 showing the relative $/kg of various LV’s. My values for SLS are significantly less than the ones of this chart but they are still very high: $32,000/kg instead of the $45,000/kg from the chart. FH with all other servicing costs combined is set at $4,000/kg on the chart. Over the life of SLS program represented by the values expressed in the chart from now to 2031 for SLS launching 9 times for ~900mt of LEO equivalent payload capacity an FH could launch 7,200mt for the same funds spent in 136 launches over the same period. That is for FH launches starting in 2015 through 2031 (17 years) an average of 8 launches a year. Or approximately the equivalent of the ISS total weight every year!!!!!

If you used FH to launch 3,000mt (3 times the amount that SLS would launch) of LEO equivalent payload capacity for a total of $12B then you would have $20B left to do payload development using the same total amount ($32B) to be spent solely on SLS during the same period of now through 2031.

At some point SLS congressional opponents will see this chart and point it out to other congressmen leaving SLS hurting for support. But I doubt anything will change leaving the result still being a decision based on jobs and not on how cost efficient it will be.

Offline alexw

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Hydrolox is highly efficient [...]
    In what sense do you mean "efficient"?

It's not space efficient at all -- it's the lowest density, ie bulkiest fuel.
Generally leads to low-mass-fraction stages.
Generally not efficient for ground operations.

Cost efficient? Well, the Soviets and Russians have never used it on upper stages, despite clearly developing hydrolox propulsion more than two decades ago.

The United States mostly didn't use it for ELVs, either, until quite recently. Atlas-Centaur, yes, but not Delta, not Delta II, not any Titan I, II, or III save the handful of IIIE, or even many of the Titan IVs. Instead, the US used kerolox and hypergolics (with performance inferior to the Russians) and solids. Delta III and IV are quite recent, but not especially successful (in terms of number of launches). Shuttle flew not a single hydrolox upper stage in three decades. SpaceX and Orbital still don't, nor any concrete published plans to do so.

Hydrolox is the most mass-efficient for high energy trajectories, and Centaur has long been the USA's trump card for planetary missions -- but not necessarily the workhorse. The the cis-lunar trajectories you are interested in don't seem to be particularly high-energy.
   -Alex

Offline HappyMartian

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And why should an Orion spacecraft take a detour route to an L2 space station and then back to the Moon and expose its crew to many more days of radiation and risk than would be the case with a direct Apollo style flightpath to the Moon?

Not many more days, one or two more days, and there would be no great increase in radiation risk. I thought we'd been through this before. A crew capsule (not necessarily Orion, it could be Dragon or CST-100 too) would need a storm shelter against SPEs anyway and for the short durations involved GCR is not an issue.

Nope. We haven't been "through this before" because no one really answered the questions I posed. Clongton came close.

There are only 3 practical ways to achieve any point landing on the lunar surface:

1. Direct flight ground to ground from the earth to the moon with no stopover in LEO at all (YMMV on this one)
2. Stage the mission at EML-1
3. Stage the mission at EML-2

There are only 2 practical ways to get off the moon from any location at any time and get home to earth:

1. Launch to EML-1, then go home
2. Launch to EML-2, then go home

All equatorial lunar orbits (LLO) require large plane changes when launching from mid and high latitude lunar sites except sites directly under the equatorial orbit track.

All polar lunar orbits (PLO) require large plane changes when launching from anywhere on the lunar surface except sites directly under the polar orbit track.

Until we have nuclear powered landers with massive margin that are capable of round trips from HEO directly to anywhere on the lunar surface and back, the Lagrange locations are the only practical way to gain any-location landing with anytime return.

All earth and lunar orbit tracks are constantly phasing with only one (1) earth-moon trajectory solution at a time without plane changes. The only way to negate this is staging at EML-1 or EML-2.

I added the bold to Clongton's comment,"All polar lunar orbits (PLO) require large plane changes when launching from anywhere on the lunar surface except sites directly under the polar orbit track." Note also that his comment, "There are only 2 practical ways to get off the moon from any location at any time and get home to earth:" is irrelevant to the critical issues of a permanent presence on the Moon and extensively exploring the Lunar surface which could be made affordable by fully exploiting the benefits of polar ice and the ISRU production of hydrolox. Polar ice and volatiles are located at "sites directly under the polar orbit track."


Haven't seen this posted here yet:

Quote
01 October 2012
Novel L2 Lunar Lander Design Released by SpaceWorks
http://www.sei.aero/eng/papers/uploads/archive/SEV-L2-Lander-Presentation_1Oct2012.pdf

SpaceWorks has published the results of an internal study of a lunar lander concept to support missions from Earth-Moon L2 to the lunar surface. The preferred concept consists of a two-stage reusable lander powered by Lox/LH2 rocket engines.

NASA is considering human exploration architectures with bases at L2 among other locations. SpaceWorks supports the idea of cislunar space as the next destination for human exploration.

Page 31, Future Study

Quote
Evaluation of alternate orbital basing locations including Low Lunar Orbit, Earth-Moon L1, GEO, and other high Earth orbits
• Compare those alternate basing options with the E-M L2 option explored here


SpaceWorks doesn't seem to be fully ready to buy into an L2 basing option, do they?


The benefits to robust Lunar science capabilities and our future missions to asteroids, Mars, and Ceres are best served by first doing ISRU hydrolox production at a Lunar polar base to enable sortie 'hop' missions by reusable Lunar Landers to many sites across the Moon's surface.

Lunar Landers and Orion spacecraft do not need anytime return options to Earth. Lunar Landers do need cheap and readily available hydrolox propellant from an ISRU facility. Reusable Lunar Landers won't fly sortie missions across the Moon's surface very often if their hydrolox propellant has to be hauled from Earth after developing a costly and politically short-sighted Human Space Exploration Architecture Using Commercial Launch/Propellant Depots


Instead, Lunar derived hydrolox propellant from a robot built polar facility is precisely what would enable a direct and radiation exposure limiting fast and affordable single SLS launched Orion spaceflight to Lunar polar orbit to meet a Moon based reusable Lander.

ISRU hydrolox production on Phobos and Mars will enable extensive sortie 'hop' science missions by reusable Mars Landers to many sites across the Marian surface.

The Mars orbiting main spacecraft and its Landers, like the Orion and its Lunar Landers, will lack the ability to leave  "any location at any time and get home to earth". However, those Mars Landers will be able to fly back to their ISRU base on the Martian surface at any time and load up on propellant and supplies, and then fly up to the main spacecraft that is orbiting Mars.

ISRU hydrolox production on Ceres will enable similar sortie 'hop' science missions by reusable Landers to many sites across the surface of Ceres. The Ceres orbiting main spacecraft and its Landers, like the Orion and its Lunar Landers, will also lack the ability to leave  "any location at any time and get home to earth". But those reusable Landers will have all the many benefit of an ISRU hydrolox base on the surface of Ceres.

Water is widely available in our Solar System. Missions between the Earth and the Moon, or on toward more distant orbs, can be made much more robust and scientifically productive, and also more affordable and sustainable, by being based on the knowledge, experience, and propellant gained from a robot built Lunar ISRU hydrolox production facility.

Hydrolox is a doable high efficiency chemical propellant combination that we have gained thirty years of valuable and extensive experience with on the reusable Space Shuttle. Not to use hydrolox would be foolish and add costs that are not justifiable or logical.

Cost is what has us chained to the Earth. The overall goal for a Human Space Exploration Architecture must be to directly and from the beginning do everything possible to reduce the costs of spaceflight. No other Human Space Exploration Architecture paradigm makes any sense at all. The skill of making hydrolox on the Moon and providing that propellant to spacecraft throughout cislunar space is what will break the cost chains that have held us back from exploring Mars and Ceres.

Currently, the folks who are pushing an L2 space station are also pushing the use of methane as a propellant. Methane may eventually be used as a propellant in some situations, but at this time there is no reason to base a Human Space Exploration Architecture on methane, and there are many costs, risks, and unneeded radiation exposure reasons to avoid using both methane and its associated L2 space station exploration architecture.

For the record, my original points still stand as far as I can tell:

.....
Note the PDF referenced by Proponent:



* 071210 Cislunar Trajectories--Cadenas, van Damme & Centuori.pdf


However, thinking about time and the Orion spacecraft and Lunar Lander missions does lead to some questions based on Proponent's referenced PDF.

TRAJECTORIES TO/FROM THE EARTH-MOON LAGRANGIAN POINTS L1 AND L2 FOR THE HUMAN EXPLORATION OF THE MOON   By Raúl Cadenas, Carlos Corral van Damme, Simone Centuori


Page 5

"EML2 located beyond the Moon

∼450000 km from the Earth

∼65000 km from the Moon

No advantages as staging node and it complicates the system
–Only option for continuous communications with the far side of the Moon"


Page 20

"CONCLUSIONS

When considering the requirements of manned missions (fast trajectories, safety, etc.), a staging node at EML1,2 is not as favourable as other options (node in LLO)"



See the Chart on Page 9

1. Are the Orion missions going from Earth to EML2 and returning to Earth from EML2 going to use direct transfer passes in front of the Moon with a one way total change in velocity of 4.25 to 4.38 km/s from LEO and a one way transfer duration of about 4 days? That higher than needed one way velocity reduces flight time and gives a minimum Orion Earth to EML2 and EML2 to Earth transfer route mission time of about 8 days and a total of 8.5 to 8.76 km/s velocity requirement. 

2. Or are the Orion missions going to EML2 and returning to Earth from EML2 doing a slower and indirect transfers with a powered swing by at the Moon (periselene at around 110 km) and total change in velocity of about 3.47 km/s and one way transfer duration of about 8.8 days? Doubling that one way duration low velocity flight time gives a minimum velocity Orion Earth to EML2 and EML2 to Earth transfer route mission time of about 17.6 days and a total of 6.94 km/s velocity requirement. 

3. Will the LM Lander, with the Orion spacecraft, be using a low velocity and efficient EML2 to Moon one way transfer flightpath with a duration of 3 days and with a similarly efficient return trip flightpath of 3 days for a total of about 6 days of deep space flight away from the EML2 space station for the Orion and the LM Lander?

4. If the Orion takes the lowest velocity routes from the Earth to EML2, 8.8 days, and then from EML2 to the Moon, about 3 days, and then from the Moon back to EML2, about 3 days, and then back to Earth, about 8.8 days, for a total of over 23 days, is that a prohibitively long mission duration that exceeds the designed Orion Mission capability of 21 days, and thus also making claims about EML2 space station enabling low total velocity requirements for missions to the Moon as somewhat meaningless? 

5. Would the lowest velocity routes that take about 8.8 days from the Earth to EML2 and then about 3 days from EML2 to the Moon for a total of about 11.8 days impose real boil off issues for using a hydrolox based lander such as the proposed Altair lander or the cargo lander version based on the Altair's hydolox decent stage?

6. Quicker routes to EML2 and then from EML2 to the Moon and then from the Moon to EML2 do exist for the Orion and LM Lander stack, but would those higher velocity routes impose an unreasonable velocity burden on a reusable hydrolox Altair or other hydrolox LM Landers or tankers or other spacecraft?

7. Is a more distant EML2 space station based space exploration architecture perfect for Lunar hydrolox based LM Landers or does it simply add liquid hydrogen boil off issues and complexity and longer than needed flight times for efficient minimum time Moon spaceflights, such as were used by Apollo 11? 

9. Is the EML2 space station necessarily going to force NASA to use the less efficient but easier to store liquid methane and liquid oxygen propellants for the rocket engines for the LM Landers, delay doing ice based ISRU hydrolox propellant production on the Lunar polar regions, and thus drive up even further the already very high costs of doing Lunar missions and provide a further justification for not doing Lunar missions?

10. If the justification for sending Orion to EML2 is not favorable to hydrolox based missions and NASA doesn't even have enough money to send robotic rovers to the Lunar surface to ground truth the Moon's polar ice deposits, could the EML2 gateway space station simply be this Moon detesting administration's classic 'bait and switch' political game that won't do anything to help build a bipartisan, affordable, and sustainable Moon exploration program?


I added the bold.
....


It is worth reviewing once again this quote from the authors of the paper that is the focus of this thread:

Evolved Human Space Exploration Architecture Using Commercial Launch/Propellant Depots  By Dr. Alan Wilhite, Dr. Dale Arney, Christopher Jones, and Patrick Chai
At: http://www.newspacewatch.com/docs/IAC-12.D3.2.3.x15379-NASAStudy.pdf

"Based on current budget projections for NASA, a flat
line budget of $3B to $4B seems to be more realistic.
Even with the commercial launch/propellant depot
having 32 percent less cost, either the Near-Earth
Asteroid program needs to be scaled back or a less
aggressive program like lunar science and in-situ
resource development may be a better choice.
"

I added the bold.


Despite the length of this post, the central question remains clear.

Do we want a Human Space Exploration Architecture based on affordable and doable "lunar science and in-situ resource development" or do we want to promote various cost generating systems that add unneeded risks, severely limit the science that we can do at distant destinations, and will not get us to a "Near-Earth Asteroid", Mars, and Ceres under the "current budget projections for NASA"?



Cheers!


Edited.

 
« Last Edit: 10/16/2012 02:56 pm by HappyMartian »
"The Moon is the most accessible destination for realizing commercial, exploration and scientific objectives beyond low Earth orbit." - LEAG

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