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#226 2004-12-18 18:38:20

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
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Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

What would be the crew and cargo capacity of the mini-shuttle you mention?

4 person and no cargo at all, not even carry-on luggage. If an astronaut wants to bring personal items (like a toothbrush) the mass budget is 185 pounds for body weight plus luggage. One or more seats could be replaced with a duffle bag of cargo, strapped to the floor bolts that held the seat. Mass of bag plus cargo equal to one astronaut body weight, ACES suit, plus seat. Instead of a seat or duffle bag, it could carry a frame to hold science drawers for/from the science module of ISS.

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#227 2004-12-18 18:57:08

Dayton3
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Registered: 2002-06-03
Posts: 126

Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

What would be the crew and cargo capacity of the mini-shuttle you mention?

4 person and no cargo at all, not even carry-on luggage. If an astronaut wants to bring personal items (like a toothbrush) the mass budget is 185 pounds for body weight plus luggage. One or more seats could be replaced with a duffle bag of cargo, strapped to the floor bolts that held the seat. Mass of bag plus cargo equal to one astronaut body weight, ACES suit, plus seat. Instead of a seat or duffle bag, it could carry a frame to hold science drawers for/from the science module of ISS.

I"d have preferred something that could carry a crew of five and perhaps at least 1,000 lbs. of cargo.

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#228 2004-12-18 19:43:15

Mad Grad Student
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From: Phoenix, Arizona, North Americ
Registered: 2003-11-09
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Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

Hmm, I hadn't heard of Mars Hybrid Direct before, but it seems to make a good amount of sense. If straight Mars Direct can be done from the surface without breaking the mass bank that would clearly be a better system as it requires one fewer launch and spacecraft, however it seems to be a widespread belief that the mass requirements of MD are too stringent, so Mars Hybrid Direct would be the next best alternative in that case.

The single floor hab is plenty big enough, and a crew of four would likely be capible of getting the job done. I would prefer a crew of at least five, I don't share Zubrin's belief that a pilot is completely unecessary for a Mars mission, but if we're willing to sacrifice one scientist or engineer a crew of four would probably work. Then again, we've all seen how underestimating minimum crew size worked for the ISS... Five crew is probably the minimum to get serious work done, but the hab would probably only have to be expanded a marginal amount to fit an extra person.

I agree that as many elements as possible should be reusable from the absolute begining of the project. The hab obviously can't be reused (except perhaps by future Mars crews on the surface), but while it would waste some fuel it's concievable that the MAV could be brought with the ITV back to Earth. In that case it would simply be a matter of reentering the ITV and aerobraking the MAV into LEO, then re-launching both to Mars at the next window. Compared to the benefits given by not needing to build a completely new spacecraft for every flight, the extra costs (monetary and mass) of making the ITV and perhaps the MAV would most likely be worth it.


A mind is like a parachute- it works best when open.

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#229 2004-12-20 13:56:42

GCNRevenger
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From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

"The ERV in Mars Semi-Direct has to haul a considerable amount of propellant all the way from Earth to Mars orbit. That's a lot of mass, that could be avoided almost entirely if it were made on Mars. Going direct from the surface yields more payload capacity and hence more possible science return, as well as fewer launches and hence less chance for failure."

No it doesn't, because MarsDirect has to haul the entire ERV into Mars orbit instead of just a CEV capsule and rocks. The modest amount of fuel required for the ERV's return trip and the increased mass budget for the ERV make the DRM style worthwhile. It also includes the possibility for making the ERV reuseable when a perminant base is started.

"doubt that many other people here can give a better guess than I can"

NASA does. The current V3.0 ERV weighs about 30MT not counting TEI stage. The MarsDirect ERV sans TEI weighs less then a Soyuz capsule. The difference is obvious... A nuclear submarine or an antarctic base is positively roomy compared to the HAB, where its biggest room is hardly a 4m triangle and its lab is half the size it should be... There isn't even enough room for seperate with-gravity staterooms on the ERV.

"If Zubrin's mass estimates are on the low side we can always use a bigger booster or go nuclear, but no matter what the system will mass more with semi-direct and the science return will be less per pound."

No you can't. Ares is as big an SDV as it gets, and going with a clean-sheet superheavy HLLV would require throwing away all the work done on Ares, a political impossibility. As far as nuclear engines, even with them MarsDirect is a bit too small to be anything more then a Martian crew taxi. Zubrin also calls for an NTR engine much bigger then what NASA does, which would be expensive to build as new facilities would be required unlike the small ones for DRM.

"...if the day after the first landing everyone at NASA starts lobbying congress with the next scaled up hardware it would at least stand a fighting chance of making it off the drawing board."

I think that NASA would have a much better chance of asking for scaled up equipment BEFORE going to Mars instead of going to Mars under the guise of science, throwing away the better part of the engineering (launcher too expensive, landers too small, aeroshells too small, etc etc), and then saying "oh we actually wanted to build a base."

I am very uncomfortable with using a superconducting ring as a particle radiation shield, as it would be an ACTIVE system... if it were to break or the coolant leak, it would be catastrophic and the crew would fry. Its too risky...

Overall, I think you are making the mistake of simply saying "oh it'll be okay, we'll think of somthing" in order to justify using an arcitecture which is simply not good enough to even get crews back safely for the sake of saving a buck... and perhaps the fun of showing NASA engineers that they are backward and obsolete...

I'd like to mention a fundimental break with Bob Zubrin, as illustrated by his congressional testimony:

"Keep it small enough to be affordable, and let's get moving now. Keep it within NASA's current budget, and possible in just a few years."

I think that the constraint of keeping the mission "affordable" within only a few years of NASA budgets is a mistake, that amount of money is insufficent for safe four-man mission of any kind, and would have no capability beyond flags/footprints. Instead, NASA should be looking slightly longer term, a decade lets say, to build an arcitecture which serves the purposes of exploration AND with enough capacity for heavier lift and larger crews needed for the "McMurdro" phase to follow.

Since heavy lift (target 40-50MT to surface) will be required, NASA DRM is the best option and has the most potential for future upgrades (reuse the ERV, build Martian RLV for crew, delivery of future cargo RLV)... plus won't break the bank.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#230 2004-12-20 14:04:07

John Creighton
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From: Nova Scotia, Canada
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Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

I think that NASA would have a much better chance of asking for scaled up equipment BEFORE going to Mars instead of going to Mars under the guise of science, throwing away the better part of the engineering (launcher too expensive, landers too small, aeroshells too small, etc etc), and then saying "oh we actually wanted to build a base."

You think the launcher will be to expensive? As for the landers being to small and the aeroshells being to small, are these things hard to scale?

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#231 2004-12-20 14:29:32

RobertDyck
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From: Winnipeg, Canada
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Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

I'd like to mention a fundimental break with Bob Zubrin, as illustrated by his congressional testimony:

"Keep it small enough to be affordable, and let's get moving now. Keep it within NASA's current budget, and possible in just a few years."

I should point out that those are my words. That's the impression I got from Dr. Zubrin's testimony, not his exact words. You can read Robert Zubrin's testimony at this Mars Society web page; it's 5-6 pages long.

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#232 2004-12-20 14:47:47

GCNRevenger
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From: Earth
Registered: 2003-10-14
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Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

Ares is the wrong size of rocket, it is both too small to send heavier payloads to Mars that are required for a base, but it is too large to send them in two seperate flights NASA DRM style (with NTR anyway).

Anyway, I want to add that I still am adamant that we have to abandon the "cut off the toothbrush handles" notion of travel to Mars. If a system requires more mass, like radiation shielding, then it does. That is the price of doing business.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#233 2004-12-20 14:57:01

John Creighton
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From: Nova Scotia, Canada
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Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

What are the possible configurations for Ares, how many metric tons to orbit would each configuration deliver and what would be the price per pound to LEO for each configuration? I just want to see how realistic or unrealistic two Ares launches is. How does this compare to other vehicles, shuttle derived, clean slate design and EELV.

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#234 2004-12-20 15:15:54

GCNRevenger
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Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

Ares is Ares really, there isn't but one base model that uses chemical engines.

Ares is the largest of the Shuttle-derived concepts, a modification on the "Shuttle Z" concept to reduce changes to the launch pad. It uses a pair of the yet unflown "advanced" Shuttle SRBs (not the 5-segment heavies) and four SSMEs in a side mounted pod. It comes with an inline upper stage powerd by a fifth SSME most likly, and is capable of placing 120MT into LEO. It is well suited to Earth escape missions with its powerful upper stage too. However, it will very likly be a beast to build, requiring the upper stage and boosters to basically be built new, and will likly cost somewhere between Shuttle-C and Clean-sheet "Superheavy." It will also likly suffer a high per-flight cost because of the use of expensive SSME engines.

The other three options are:
1: Shuttle-C, 80-100MT to orbit but no Earth escape flights as it lacks an upper stage. Lowest development cost and good versatility for smaller loads, but per-flight costs could prove to be high as it is an SDV. Low practical flight rates too.

2: Clean sheet "light" HLLV, target of 80-100MT to orbit, probobly based on the Atlas-V with uprated engines or a multiengine Delta core with some sort of boosters. Intermediate to high development costs, but low per-flight costs. High practical flight rates are also possible.

3: Clean sheet "super" HLLV, target of 200-250MT to orbit, intended for single throw heavy lift missions. High development costs, intermediate to high flight costs, but you get alot of bang for the buck, likly the most payload per flight dollar. May prove more useful in the future if superheavy payloads are required for other things, but limited application to smaller things.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#235 2004-12-20 16:11:12

Dayton3
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Registered: 2002-06-03
Posts: 126

Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

I've about settled on a "Super Ares" design with four, 5 segment SRBs along with 5 RS-68s on the base of a heavily modified External tank and a single RS-68 upper stage.

I've heard that the LEO capability would be something like 475,000 lbs. and payload delivered to the Mars surface would be something like 75,000 to 80,000 lbs.

I believe that is large enough for an Earth Return Vehicle supporting a five man crew adequately.

What would it cost?  Probably on the order of 10 billion dollars.  Spread over five years thats only about 2 billion a year.  With each production model booster of around 1 billion dollars.  Given you need an average of one booster built per year for Mars Direct, that is all well within NASAs current 14 billion a year budget.

Personally, I would plan on two "Super Ares" boosters per year so you could also launch long duration lunar flights and boost extremely large space station segments to LEO.

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#236 2004-12-20 16:23:08

GCNRevenger
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From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

"I've about settled on a "Super Ares" design with four, 5 segment SRBs along with 5 RS-68s on the base of a heavily modified External tank and a single RS-68 upper stage."

I know. It was my idea... A means of fulfilling that NASA DRM V1.0 requirement for a superheavy rocket using exsisting engines. DRM employed a six man crew and could deliver 40-50MT payloads roughly with NTR TMI stage.

It would likly cost like $10-15Bn and a billion each per flight, yes. Probobly more expensive then light clean sheet to develop (perhaps a little higher per-pound cost though), but as far as competition with SDV... the cost per flight for Shuttle-C or Z is a question mark.


"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw

The glass is at 50% of capacity

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#237 2005-02-15 12:44:13

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 17,741

Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

Though some things where and somethings where not addressed to satifaction of thoses that have had the opertunity to read them. Has growing food been or the means to create a green house been for the down mass limits would be met in the first mission and little would or could be taken to help the crew.

How about this item being adapted to make a greenhouse though these are for infection control. I see that they are very portable and flexible in there construction.

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#238 2019-12-25 16:50:55

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 17,741

Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

Bump need to fix old topic:

We have had a few of these topics since my time here on newmars and a few have been swallowed by the great crash. We know from the level of planning that we need better if we are going to stay but its the lift vehicle which cause us to be cautious on the journey to mars. We also need to gained knowledge on micro gravity diseases for the long stays in space and on mars for man.

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#239 2019-12-25 18:10:08

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 17,741

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