Zubrin on Moon, then Mars - Three essays, one link

GCNRevenger · 2005-03-20 12:28:30

1: You can't mine the Moon with HLLV.

Let me repeat that... you can't mine the Moon HLLV. You can't. It can't be done. Impossible... Infact, you can't mine the Moon with ANY expendable launch vehicle. In order to mine the Moon, we absolutely must have an Earthside RLV. No way around it, no matter if you can launch a dozen HLLVs. Hence, your argument is a straw-man, since neither option can do the job.

We must have an order of magnetude decrease in launch and TLI/TEI costs, crew-only ferrying, and heavy return capability. No expendable vehicle can do this, American nor Russian.

2: We don't need a dozen HLLV flights a year to build a "foothold" Lunar base. The size of payloads needed to set up a small base with 24/7 power and LOX ISRU plants won't require that we launch >1,000MT a year, 5X the mass of the whole ISS. That is an absurd statement. A TransHab module weighs around 8MT, a 2,000kWt nuclear plant around 10MT, a lander only a few tonnes (dry) etc.

So, it doesn't matter if you can access high flight rates, because we won't use them. I mean, obviously!

3: EELV+ can do basically EVERYTHING that we want SDV to do for a Lunar program. For the fifth time, SDV will be flying a 40-50MT payload and a 40-50MT Translunar rocket stage. There is no difference if a 40-50MT EELV just launches these seperatly! I'm not going to repeat myself again if you aren't intending to listen, Bill...

4: "but (SDV) allows for a much less expensive ramping up or acceleration of flight rates."

The "Shuttle lie" is still not true. If you need to double the flight rate of SDV in order to clearly top EELV costs, you won't get a radical cost improvement. Because SDV is so man-power intensive, increasing the flight rate will demand that you likewise increase the launch staff size. You'll have to reopen the old unused VAB high bays, increase the SRB assembly staff, etc... I think its a fair question if the Crawler/Pad-39 could even accomodate a dozen annual launches.

"5 or 6 lunar sorties, between 2020 & 2030..."

Delta-IV production should, worst case (3X HLV & 1X Medium), be sufficent for four Lunar expeditions anually. That would be fourty flights, not six. Best case senario, (2X HLV & 1X Medium) would give you fifty worth, assuming a small increase in launch pad turnaround.

Or, you could fly only two manned sorties per year and put up 450MT (best case @50MT ea) or 315MT (worst case @ 45MT ea) of payload on orbit with no production increase. If you are launching six SDVs per year, two of which are used for crew, that leaves you with only 320-400MT of launch capacity for base building. AGAIN, no clear-cut advantage.

5: "Destroying SDV infrastructure means that a genuinely robust space program is off the table for a generation, or more."

Oh hush up and stop your melodramatic grand-standing Bill. Thats not true and you know it.

GCNRevenger · 2005-03-20 13:18:42

More on Delta-IV HLV...

Right now, it costs $180M a pop, right? Lets say it will cost $200M each with upgrades, over 10% of the unit cost for basically no major changes other then cheap GEMs and RS-68 nozzle upgrade, perhaps improved rocket fuel.

That $200M price tag is only if you are building a few per year. If NASA needs them in bulk, NASA could aquire them for much less money most likly, just like the USAF bought bulk Delta-II rockets cheap for the GPS network.

Boeing can do this better then SDV because the Delta-IV flight rate can be ramped up with less overhead costs. The booster cores are assembled in a hanger by robot arms, then mounted on a heavy truck (no resurfacing the crawler "road" with rocks for every flight), and the VAB is only a few hundred feet from the launch tower, not a mile away. They can do it faster and without as many people... What if NASA could get Delta-IV HLV's for only $150M each?

...a basic 80MT "Magnum" SDV would have to beat $300M a flight.

BWhite · 2005-03-20 13:30:31

Its all in the bean counting. No reason to be personal. ???

Today Delta IVH has flown once with a capability of 25MT for about $200 million. Everything else remains on paper.

=IF= your number hold true, GCNRevenger =THEN= you are correct.

But that is what makes it a nasty dilemma, no?

= = =

The base level Shuttle C can fly about 75 - 80 MT without upgrade per astronautix. (77,000 kg several years ago - is that with the painted tank?) No 5 segment SRBs and no RL-60 upper stage on an in-line version.

Upgrade the SRBs for a higher fuel/mass ratio and add an RL-60 upper stage and SDV ends up being very much more than 80MT.

= = =

In round figures, do we need 2, 2 1/2 or 3 EELV to lift as much as 1 SDV?

If you can use slushed hydrogen and lithium alloy and RL-60s for EELV then you must also include those upgrades within the SDV calculations.

These are questions of accountancy not emotion.

Edited By BWhite on 1111347572

BWhite · 2005-03-20 13:42:49

How much mass to LEO is added by using 4 five segment SRBs to an inline SDV?

For example?

BWhite · 2005-03-20 13:51:20

This is an interesting quote:

Kim Stanley Robinson, in an address to the Mars Society, cautioned against the disease of Freud's "narcissism of petty differences" This is the tendency, among those feeling relatively powerless in their pursuit of an ambitious, long-range agenda, to descend into factional bickering over minutiae.

http://www.spacedaily.com/news/oped-04s.html]Link

Frankly, the more we argue SDV vs EELV, the more I am coming to the belief it is six of one, half dozen of another. :;):

= = =

Okay, EELV[plus] can get fairly large but is that included within the VSE budget or is that a post-2020 "possibility"

My daugher, when she was 3 1/2 used the word "possibility" - - astonished, I asked her what she thought "possibility" meant.

"Daddy, when a baby asks for a Christmas present and her mommy and daddy say 'maybe' - - well then its a possibility she will get it"

A 45MT - 50MT EELV for $200 million might be possible IF we order sufficient volume. And ONLY if we order sufficient volume.

= = =

Back to the petty differences. The real question is how to assure we order sufficient launch volume.

12-18 50MT EELV+ flying per year would be acceptable to me.

Edited By BWhite on 1111348370

Michael Bloxham · 2005-03-20 19:48:22

Back to the petty differences. The real question is how to assure we order sufficient launch volume.
12-18 50MT EELV+ flying per year would be acceptable to me.

Now here's whats had me worried all along. Look at this, we are now concerned with ensuring an EELV will be economical by creating a work load for it. And as GCNRevenger has himself admitted, EELV's will only be good for lunar operations. So lets construct a sprawling moon-base, made up of small pieces requiring delivery on high flight-rate EELV's; EELV's that would otherwise be unattractively expensive to operate. Yup, sounds like a perfectly sane plan to me...

BWhite · 2005-03-20 22:06:04

Back to the petty differences. The real question is how to assure we order sufficient launch volume.
12-18 50MT EELV+ flying per year would be acceptable to me.
Now here's whats had me worried all along. Look at this, we are now concerned with ensuring an EELV will be economical by creating a work load for it. And as GCNRevenger has himself admitted, EELV's will only be good for lunar operations. So lets construct a sprawling moon-base, made up of small pieces requiring delivery on high flight-rate EELV's; EELV's that would otherwise be unattractively expensive to operate. Yup, sounds like a perfectly sane plan to me...

Michael, this gets at the essence of my preference for SDV.

EELV makes it too easy to scale back the VSE to a symbolic, slow motion project while the beltway politicians strut and pound their chests about people on the Moon.

Once we deploy genuine SDV, pressure will be created to actually use it.

= = =

During a slow motion implementation of the vision, EELV might save money (might!) but I do not want a slow motion implementation.

Michael Bloxham · 2005-03-20 22:10:54

My point exactly.

SpaceNut · 2005-03-21 06:47:32

What portions of the shuttle army are under Nasa's head counts and what is under the space alliance of Boeing / Lockheed? We know that it absorbs the 4.3 billion a year for only a few launches per shuttle.

GCNRevenger · 2005-03-21 09:48:33

"A 45MT - 50MT EELV for $200 million might be possible IF we order sufficient volume. And ONLY if we order sufficient volume."

But it doesn't! That ~$200M price-tag is for today's low flight rate. Delta-IV HLV goes for $180M each right now, and I think that a pack of cheap SRMs and improved RS-68 nozzles can be had for $20M more pretty easily. As far as increasing the launch rate from todays' 2-4 per year, the only place for the price-per-unit to go is down. Its already economical enough!

SDV on the other hand, you would have to cut its cost about 50% versus Shuttle to be cost competitive with EELV at its low flight rate, and probobly closer to 66% versus the "fast" rate, all while paying for the extra-large SRBs and throwing away a few large liquid engines on every shot, maintaining the huge and un-automated KSC facilities, and trying to vanquish the vestigial Shuttle Army... Also, if you intend to ramp up the flight rate, can the single working Pad-39 handle it?

I'm putting my money on EELV+

"Once we deploy genuine SDV, pressure will be created to actually use it."

Again, the old "Shuttle Lie." Build it and they will come, etc etc... And you know what happend because of this notion? The ISS happend! I would figure you to be a little better student of history Bill...

And please, please tell me how the ability to send 300MT (50% more then the entire ISS's mass) with no production or launch pad improvements, to Lunar orbit anually with EELV constitutes "slow motion."

John Creighton · 2005-03-21 15:07:28

And please, please tell me how the ability to send 300MT (50% more then the entire ISS's mass) with no production or launch pad improvements, to Lunar orbit anually with EELV constitutes "slow motion."

That should pretty good. That would be 3 EELV+ per mission at 2 missions a year. Of course that is not what will get to the moon since some of that mass will go to supporting people on the flight to and back from the moon.

Say one 8th of that reaches the moon (rough guess). That would be about 37 tons landed on the moon per year and it would take 5 years to build up the same mass on the moon as the ISS. Maybe not "slow motion" but not that fast either.

BWhite · 2005-03-21 15:48:18

Has either Pad 39A or Pad 39B gone out of service? Boeing has one pad in Florida SLC 37 and one at Vandenberg, correct?

But Vandenberg can only launch to high inclination and retrograde (towards the west) correct? Range safety issues?

= = =

Obviously I lack access to massive amounts of data NASA will have available. Based on my limited access to material, the idea of a Delta IV Medium (1 barrel plus small solids) for CEV does make sense.

CEV alone is not sufficient for a lunar mission. You need CEV plus a TLI stage. Then you need a lander plus TLI stage.

How much fuel does a lander need? Lander plus TLI plus lander fuel (down and up) would seem to press the 45-50MT totals rather quickly. And using disposable architecture, we throw it all away come 2025.

Unless we go with the 45-50MT "tricked out" version of Delta IV from the very beginning, we will need at least 4 launches per lunar mission.

= = =

Edit:

Two Delta IV super plus can place a smallish disposable lander in the Moon, right? With one super plus for CEV and TLI and the other for the lander and TLI and lunar descent/ascent how do we land materials for any permanent presence?

How fast can Pad 37 cycle?

("Super plus" equals the 45-50 MT variant which strikes me as absolutely necessary for EELV to make any sense at all)

= = =

How do we scale up to a larger lunar lander if we use EELV?

Edited By BWhite on 1111442124

BWhite · 2005-03-21 16:09:28

Zubrin's QQ argument fails =IF= we deploy 45-50MT EELV for the very first lunar mission. Then only two launches are required followed by a lunar orbit rendevouz (LOR) mission.

But at 45MT, the lander plus TLI stage starts entering the realm of "chop off the toothbrush handles" - - not a good thing, right?

Therefore, immediate deployment of the "tricked out" EELV should be a condition precedent to choosing EELV over SDV. And if "tricked out" means 43.5 MT, then its too small.

= = =

And Zubrin remains correct that having an astronaut babysit the CEV in LLO is wasteful.

= = =

A larger lander could be used if 3 launches were employed but do we have payload fairing issues for larger landers?

Edited By BWhite on 1111443347

BWhite · 2005-03-21 16:47:08

Is Zubrin wrong about this:

Developing a Lunar base will also require delivering substantial cargo one-way to the Lunar surface. Here the DR scenario has a large advantage over LOR, since it can use the same large standard lander to deliver substantial habitat modules or other large cargo elements to the surface as it employs to deliver the fully-fueled CEV.

In the 2nd essay Zubrin proposes a landing "cab" to carry the CEV to the lunar surface and back up for return to Earth. Launch the entire thing on a single HLLV shot. Using ISPP, 70MT is said to be sufficient.

Zubrin asserts that a DR mission architecture allows triple the cargo to be delivered to the luanr surface.

Argument? Show your work. :;):

= = =

If EELV-only LOR missions are intended as "scout missions" and precursors to future DR missions, why the intermediate step?

Edited By BWhite on 1111445300

Michael Bloxham · 2005-03-21 17:09:03

SDV on the other hand, you would have to cut its cost about 50% versus Shuttle to be cost competitive with EELV at its low flight rate, and probobly closer to 66% versus the "fast" rate...

66%? Thats a 1/3 reduction in expenditure over shuttle... Without the plagued orbiter, this sounds achieveable to me.

Again, the old "Shuttle Lie." Build it and they will come, etc etc... And you know what happend because of this notion? The ISS happend!

Isn't that a contradiction?

The way I see it, with EELV's we may be in danger of recreating ISS on the moon, but wouldn't it be great if we could do the same on Mars ?

We cannot continue to argue EELV's versus SDV's. We're simply not comparing apples to apples. Because EELV's can't get us to Mars, and SDV can. This changes everything. In my mind, the matter of concern should really be Moon vs Mars.

And that's an easy one, isn't it? :;):

GCNRevenger · 2005-03-21 19:04:22

"66%? Thats a 1/3 reduction in expenditure over shuttle... Without the plagued orbiter, this sounds achieveable to me."

No, thats a 66% cut from its current per-launch price, I.E. the price having to be about one-third of today's ~$1Bn Shuttle launch.

"Because EELV's can't get us to Mars, and SDV can. This changes everything"

Wrong. You don't know that SDV can do the job for a low enough cost. If SDV costs like $700M a pop to fly, we'll never make it to Mars beyond a few half-insane radiation dosed astronauts doing flags & footprint missions, vainly looking for bugs in the bone-dry dust with simplistic chemical sensors that we could have just flown on robots...

Anyway, with Mars being 25 years away give or take, that would be plenty of time to build a new rocket that is best suited to the task, instead of trying to jerry-rig the antique Shuttle program to kinda-sorrta suffice. In the mean time, we ought to go with the best option for the Moon and only the Moon, which until I hear credible cost estimates for SDV, would be EELV+.
---------------------------------------------------------------------
Now Bill, I find it awfully hard to reconsile how you have gone from "need determines everything" to flailing about and imposing superior performance constraints on EELV that it be clearly superior to SDV and not just on parity.

SDV cannot exceed ~100MT of payload without the addition of a very powerful (and expensive) upper stage, and that is with the big 5-segment SRBs and such.

In such a case, Delta (or Delta+Atlas) could deliver the same payload to orbit with three launches even at the low end of the upgrade range. Two 40MT shots for the Lunar lander and the TLI stage, followed by a single 20MT medium shot for CEV+TEI. The TLI stage would be "extra large," perhaps supplimented with a little tankage on the lander payload. Anyway, 100MT to orbit same as SDV.

At 45 or 50MT each, you would actually come out ahead of a single-flight SDV mission. If you went with four launches, 2-3 heavies and 1-2 mediums, then you come out way ahead of SDV. If Delta-IV+ HLV comes out to be like $150M a pop in bulk, then Delta could soundly defeat a half-billion SDV flight. 40MT is big enough to match SDV.

Zubrin also makes (close to absurdly) big assumptions about the efficency advantages of direct flight versus departure from LEO. In such a case, then a few extra tonnes of fuel provided by a more-then-40MT EELV+ should make up this difference nicely.

Edit, additional:

"But at 45MT, the lander plus TLI stage starts entering the realm of "chop off the toothbrush handles" - - not a good thing, right?"

No. SDV would deliver the same mass to the Moon. Maybe less. Roughly half the mass sent to Lunar orbit is fuel for TLI, give or take a little for OMS and different engine Isp. It doesn't much if you launch 100MT up in two 50MT flights or one 100MT flight.

Michael Bloxham · 2005-03-21 19:38:25

I honestly don't give a rats ass how cheap we can 'do the moon'. The moon is simply not worth doing.

BWhite · 2005-03-22 07:22:55

Anyway, with Mars being 25 years away give or take, that would be plenty of time to build a new rocket that is best suited to the task, instead of trying to jerry-rig the antique Shuttle program to kinda-sorrta suffice. In the mean time, we ought to go with the best option for the Moon and only the Moon, which until I hear credible cost estimates for SDV, would be EELV+.

Stop saying stuff like this or I rejoin Michael Bloxham. :;):

If Moon-Mars isn't ONE WORD, if its Moon now and Mars, well someday far away, I might very well join the "robots only" people. Or start screaming "Emperor's New Space Program"

Also, ISRU must not be for lunar mission #6 or #7. ISRU and ISPP must be employed from the beginning, or I return to chanting "Emperor's New Space Program" - - and the equipment used for the Moon MUST be designed for a logical progression to Mars capable gear.

If it is Moon now and we design new stuff in 25 years, then I will OPPOSE the effort with extreme vigor.

Also 50MT EELV are a condition precedent and MUST be deployed for the VERY FIRST lunar mission, at $200 million per launch.

If payload creeps down to 45MT or 42MT and the price creeps up to $210 million or $225 million, then its time to put some Boeing executive in JAIL if these promises induce cancellation of SDV!

= = =

Before SDV is off the table, Boeing needs to PROVE they can deploy large quantities of 50MT Deltas for a guaranteed price of $200 million or less.

Otherwise, IMHO, no deal.

SpaceNut · 2005-03-22 08:16:23

What would the down mass requirement for a lander on Mars be for the calculated crew size and other items total. Also is it possible to split that lump sum into managable pieces or must it be geared at what ever the largest non manned item to be brought to the surface by this lander.
In other words start with the end (moonmars) to design the ship size and shape from what we know we will require.

GCNRevenger · 2005-03-22 10:10:49

As much as I wish it wern't true Bill, i'm not sure how realistic our desire that Lunar and Mars programs are not really seperate entities... Getting a Mars expedition started isn't quite 25 years away, but it isn't going to be the day after we set foot back on the Moon either... Anyway, I think you are trying to impose an idealogical/political constraint to what should be a bean-counter-only decision about the choice of launch vehicle. I also find your unwillingness to think anything bad about SDV strange and confusing.

"Also, ISRU must not be for lunar mission #6 or #7. ISRU and ISPP must be employed from the beginning"

I assume you are referring to Bob's Direct Return mission design... This just isn't possible Bill, a Lunar LOX plant is not a light weight device. You can possibly bring the plant (reactor, diggers, sorters, furnace, pumps, cryocoolers, insulated tanks, plumbing) or Earth-return fuel. If you want to send the plant seperatly, you will need to send a crew with return fuel to assemble it, since I think that is beyond the abilities of robots.

Bob is also selling snake oil if he means that the very first mission could deliver enough mass for an extended stay, that just isn't happening. An inflatable HAB module would weigh about as much as the CEV does, and would weigh a signifigant fraction what the ISRU plant does. The fact that he doesn't state that this obviously isn't happening on the first trip suggests that he is being deceptive with his mission capabilities, just like MarsDirect's baloney mass estimates.

Oh, and Bob's plan already assumes the use of Ares if you would notice. Building Ares or other "extra heavy" SDV will not be cheap: nobody has ever built an upper stage with such a heavy engine, not even Russia's Energia. The extra weight and height would make the SDV development much more complicated. It definatly won't be cheaper per-pound then "regular" SDV or EELV+. I would also point out that an Ares-class SDV is all the wrong size for a Mars expedition, since it is too small for a direct flight but too big for a two-shot arcitecture.

Speaking of EELV+ vs SDV again... Hey Bill, what happens if SDV doesn't live up to its pitch? What if it only carries 90MT (new boosters) or 70MT (old boosters)? What if it can only be flown four or five times a year instead of six? What if it costs $600-700M instead of $400-500M a pop?. If that happens, we should throw Michael Griffin in jail if the capable and exsisting Delta-IV is downselected!... You being hard on EELV+ but taking on faith that "SDV can do it™" doesn't make any sense to me.

"Before SDV is off the table, Boeing needs to PROVE they can deploy large quantities of 50MT Deltas for a guaranteed price of $200 million or less."

Before SDV is ON the table, NASA needs to PROVE they can deploy large quantities of 100MT Magnums/Shuttle-B/etc for the guaranteed price of $400M or less... Here is where EELV+ has the edge, because it exsists and we know with reasonable certainty that it will be affordable. If it costs $180M now for 2-3 a year, then $200M each with some cheap modifications for a dozen a year is an economicly sound assumption, especially considering the superior level of automation that Delta processing has.

Flying the Shuttle Stack, with an additional ~$75M in expendable hardware ($10M for bigger boosters, 3X RS-68, 2X RL-60, avionics, payload faring), for only ~40-50% of current price, THATS a gamble. Oh, and don't forget to add the $3-5Bn development costs over its ~100 or so lifetime flights, which tacks on another $30-50M each... Unless development costs lots more then it was supposed to like most Shuttle projects.

A word about sustainability too, which you were earlier at least ranting about Bill... That just making the majority of Earth-return fuel on the Moon will improve matters, but its not enough. Reuseability is key here, that there is a worthwhile intermediate level of reuseability between 100% expendable and Shuttle-II 100% reuseable... which HLLV does not lend itself to. If we were to really leverage Lunar fuels (or at least LOX) then the obvious thing to do is to use that fuel for TLI and TEI. That way, we could get a crew or a payload all the way to the Moon and back for the price of a single EELV medium. EELV is also preferred if you leverage ion engines... And bank the savings for Mars.

...cool, I didn't know the trademark™ would do that

BWhite · 2005-03-22 10:30:14

Ah, the narcissim of petty differences.

Whilst we argue this, Senator Kay Bailey Hutchinson (Republican of Texas) is talking about keeping the orbiter flying until CEV is operational. Of course, spending money on orbiter will only delay CEV which requires further extension of orbiter. ???

EELV and SDV need not be decided now, because nothing final will be done until after President Bush leaves office.

A 50MT EELV-super has potential, that I will concede.

However, a commitment to ISPP and ISRU as soon as possible - - not a "wouldn't it be nice, someday. . ." - - attitude is essential for my support of the VSE, along with a shared consensus that Moon-Mars is one word, not two.

Otherwise, its back to Moon versus Mars and the circled up firing squads!

BWhite · 2005-03-22 10:35:42

Again, I like Zubrin's CEV "lunar cab" idea.

Design a versatile lander that can be mated with CEV or an ISPP plant or a supply module.

Mate CEV to the cab before stacking on top the 50MT EELV-Super and dock with TLI stage in LEO for a 100 MT mission using two launches.

Mate the cab with an ISPP plant and dock with TLI stage in LEO and deliver an ISPP plant with the same hardware and two launches.

Mate the cab with a cargo module to deliver supplies to the lunar surface. Use the cargo module to carry LOX (or PGMs) from the lunar surface.

Before ISPP LOX becomes available, send the cab/CEV combo with 2 30MT medium TLI modules. Okay, its three launches to accomodate EELV w/o ISPP.

But that creates incentive to start ISPP, ASAP.

LOR will delay ISPP because human inertia will resist throwing away the LOR architecture hardware. A universal cab can be desiged once and used in a variety of roles. A disposable pressurized lander will become obsolete once true DR missions become feasible and we will need new hardware to move beyond the initial scout missions.

Edited By BWhite on 1111514398

SpaceNut · 2005-03-22 11:50:56

If the number of shuttle flights versus the amount of cash to keep it going is capped at a maxium. Then any additional years that it must fly should come from savings of not flying during any previous year. Rather eating up all the budget dollars like they have for the past 2 years approximate with no shuttle flights at all to show for the money. I figure those that are the shuttle army aught to work for free for the next few years.

SpaceNut · 2019-07-21 16:14:52

Wow 2005 and we knew that we were going to be in a heal dragging contest.

SpaceNut · 2019-07-23 19:06:06

Finally finished up with all posts repaired...

The front page of newmars has a cover story that indicated Zubrin has a plan for the moon. That said where are we with just that one step?

dated 3/2018

1. has fund raising started to be generated for this mission plan
2. are there any agreements for the launch vehicles
3. has the payloads been optimized for a mission and entered into a manifest

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#101 2005-03-20 12:28:30

Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

#106 2005-03-20 19:48:22

Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

#109 2005-03-21 06:47:32

Re: Zubrin on Moon, then Mars - Three essays, one link

#110 2005-03-21 09:48:33

Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

#114 2005-03-21 16:47:08

Re: Zubrin on Moon, then Mars - Three essays, one link

#115 2005-03-21 17:09:03

Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

#117 2005-03-21 19:38:25

Re: Zubrin on Moon, then Mars - Three essays, one link

#118 2005-03-22 07:22:55

Re: Zubrin on Moon, then Mars - Three essays, one link

#119 2005-03-22 08:16:23

Re: Zubrin on Moon, then Mars - Three essays, one link

#120 2005-03-22 10:10:49

Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

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Re: Zubrin on Moon, then Mars - Three essays, one link

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