Design Reference Mission 5.0

Dayton Kitchens · 2007-11-19 09:49:37

I assumed that you would wait for the next launch window after verifying that the fueled ascent stage had safely reached the martian surface.

The point remains that Mars Semi-Direct factors in the possible failure of propellant production on the Martian surface.

cIclops · 2007-11-19 10:37:05

In Mars Direct the ascent vehicle would be ISRU fueled and ready before the crew even left Earth, and they would have another backup vehicle available when they arrived.

This architecture has the Lander and Hab for the next mission arrive just after the crew land on the surface, so both are available as backups. Note also in the text table on page 8, that ISRU is mentioned for ascent.

If ISRU is in the mission critical path then it must be tested on Mars first to ensure it works. Producing and storing the many tons of LOX and Methane needed will take a lot of time, so the system has to operate continuously without fail.

If the ISRU unit does fail the backup unit may have the same problem. If the failure happens late in the surface mission, the crew will be lost unless they have sufficient supplies to wait for a rescue vehicle and the next return window. In the worst case this could be 26 months! The rescue vehicle will have to be a different design as its fully fueled. This is not a good plan. Better to first send a lander and test ISRU fuel production and vehicle ascent without a crew.

Dayton Kitchens · 2007-11-19 12:38:12

No matter how you design Mars Mission architecture there are going to be risks.

One of the things I've always agreed with Dr. Zubrin on was "more launches, more expense, more risks".

cIclops · 2007-11-19 13:07:02

Indeed. A good architecture will optimize risk, cost and capability trades.

<idea>
Thinking sideways ... if the ascent and descent vehicles were split before landing, both could be optimized.
</idea>

So instead of a single lander there would be two vehicles:

1 Pure lander to take crew or cargo to the surface.

2 Pure ascent vehicle that would be put on the surface first, fueled by ISRU and ready before the crew arrived.

This would allow the ascender to contain the ISRU unit and eliminate the risk of not landing near enough for refueling. Easier for the crew to go to the ascender than take the fuel to the lander. This optimizes both lander and ascender.

The ascender takes the crew to LMO where it docks with Orion and the MTV.

Dayton Kitchens · 2007-11-19 16:22:04

Indeed. A good architecture will optimize risk, cost and capability trades.
<idea>
Thinking sideways ... if the ascent and descent vehicles were split before landing, both could be optimized.
</idea>
So instead of a single lander there would be two vehicles:
1 Pure lander to take crew or cargo to the surface.
2 Pure ascent vehicle that would be put on the surface first, fueled by ISRU and ready before the crew arrived.
This would allow the ascender to contain the ISRU unit and eliminate the risk of not landing near enough for refueling. Easier for the crew to go to the ascender than take the fuel to the lander. This optimizes both lander and ascender.
The ascender takes the crew to LMO where it docks with Orion and the MTV.

Isn't that the entire Mars Semi-Direct Concept?

Mars Ascent Vehicle lands. Manufactures enough methane and oxygen to lift the crew into orbit to rendevous with the Mars Transfer Vehicle for the trip back to Earth orbit.

Fuel manufacture is verified before the Mars Hab leaves orbit with a crew aboard.

cIclops · 2007-11-19 17:32:25

DRM 1.0 and later DRM 3.0 use LMO rendezvous rather than direct to and from the surface, hence "semi direct". DRM 3.0 has the ISRU propellant unit integrated with the Hab and the ascender. The crew land separately with another Hab. This makes very big packages. Splitting it into four pieces would optimize each package. In sequence:

1 Ascender + ISRU to surface
2 Hab to surface
3 Crew + MTV + Orion + Lander to LMO
4 Crew + Lander to surface

Tom Kalbfus · 2007-11-19 17:47:07

One can always spend more to add extra margins of safety. The main problem I have with Semi-Direct is that the majority of the money gets spent returning the astronauts to Earth, this reduces the return on investment. Mars Direct on the other hand spends as much money getting the astronauts there as it does returning them. In Apollo, the majority of money wen't towards getting the astronauts to the Moon, getting them back was almost an afterthought.

So how much additional supplies could be sent to Mars for the cost of getting the astronauts back from Mars in Semi-Direct? I think that if we intend to establish a permanent base on Mars, why not send colonists and keep on adding to their number as we expand the base? If we intend for Mars exploration to be a temporary thing about "here today and gone tomorrow" then we have to consider how to get the astronauts back, but if humans can live their indefinitely and if it is cheaper to send resupplies than it is to ferry them back and send replacements from Earth, why not just plant a Mars Base/Colony in the first place? We could send new rovers, and new habs as needed, while replacing the crew every two years will multiply the cost by six.

I think Mars Semi-Direct is a case of colonization being cheaper than exploration.

Dayton Kitchens · 2007-11-19 19:37:05

I'm sure that is correct.

But could NASA ever get funding for sending a team of astronauts and not bringing them back?

I would say at least the first three missions of a Mars program will have to bring the crews back after 500 day stay times on the surface of Mars.

After three missions (12-18 astronauts total), IF the program is still going (which I think is one heck of an if) then we could focus on longer duration missions.

Tom Kalbfus · 2007-11-20 07:37:47

It would be cheaper to have the means of returning to Earth, but not use it and resupply the current mission than to send another mission from Earth. Mars Direct works best for this. It produces fuel for the return to Earth, the Astronauts can either choose to use it or they stay an additional 26 months with resupplies, their choice.

I figure what's the point of going to Mars if we are going to spend all that money to get there and then leave? Maybe we should search for people who want to be colonists, and use additional missions to add to the colony rather than replace base personel. I mean if everyone complains about the cost, then it would make sense to be frugal.

cIclops · 2007-11-20 07:52:04

But could NASA ever get funding for sending a team of astronauts and not bringing them back?

No. The first crew will be returned to see how they physically manage the mission. Perhaps if they suffer no ill effects, later crews might stay longer. It 's doubtful that any crew will be sent without the possibility of return, if they wanted this their psychological state would be questionable.

cIclops · 2007-11-20 09:25:23

Ok another idea, in sequence

ascender lands:
+ single LOX/CH4 engine
+ H2 feedstock
+ nuclear surface power
+ ISRU fuel plant that refills LOX/CH4 tanks

when refueled:

Hab lands
+ fully mobile - uses LOX/CH4 fuel
+ remote operation
+ contains 500 days supplies
+ lab

when safely on the surface and within range of the ascender:
(if not the next Hab is landed)

Crew land
+ long range LOX/CH4 rover
+ 30 days supplies
+ small lab

Goto Hab, move Hab to ascender (may need to refuel Hab or visit ISRU first to refuel)
If Hab is unreachable, goto ascender and conduct short stay mission then return to LMO

If possible the ascender will carry extra fuel and boost MTV+Orion to TEI

Tom Kalbfus · 2007-11-20 13:50:50

But could NASA ever get funding for sending a team of astronauts and not bringing them back?
No. The first crew will be returned to see how they physically manage the mission. Perhaps if they suffer no ill effects, later crews might stay longer. It 's doubtful that any crew will be sent without the possibility of return, if they wanted this their psychological state would be questionable.

I didn't say without possibility of return. They have return tickets in the form of return to Earth vehicles should they choose to use them at a given launch window, but perhaps we should give them the option of staying another 26 month with resupply. Its cheaper to resupply them than to replace the crew by sending another mission. The more people we have on Mars the more things that can be done. Getting to Earth from Mars is not as expensive as going to Mars from Earth We could just keep a return stage ready just in case. So how many people does it take to make the planet home? If we just go there for a visit and never return, what's the point? Are we going to colonize it or not? This is similar to the idea of interstellar colonization, most manned trips are conceived as one way, I mean what's the point of returning them to Earth if you return them 80 years later and there is no one living that still remembers them, and spending all that money to return them?

If we want to establish a beach head on Mars, then were going to have alot of people arriving and few people leaving. I mean whats the point in paying for round trips if what you intend to do is establish a colony? It costs enough just to set the colonists up, you mean we should pay for visitors too? If people don't want to stay, perhaps we should question whether they should be going.

cIclops · 2007-11-20 14:31:22

Until return stages are manufactured on Mars, they will extremely expensive - mostly because of the delivery charges

All this discussion of colonies on Mars is contingent on a transportation system and ensuring that people can live on Mars. That transportation system will evolve out of earlier systems that are proven and reliable. They in turn may be based on systems are being designed today or other generations in between.

Tom Kalbfus · 2007-11-20 15:46:43

I hope its not going to be generations! I hope to see an era of rapid progress like the early 20th century. Lets just perfect the technology for living on Mars and just go their. Mars is not the place for testing such technology for if it fails people die. Deterimine the reliabilty of the equipment before hand before sending any people. I think if we have until 2031, that is plenty of time to test the equipment, and by that time we should be ready to plant the first colony. We're not going to spend billions of dollars to go to Mars just to see if something works. That is basically my problem with the design reference mission as well, it doesn't use technology which could make it cheaper, it instead wastes billions of dollars going the cautious route until we can be sure we can produce propellent to fuel the return stage. I really don't think we need to be in the vicinity of Mars to test this equipment. I also think the Apollo 10 mission where they almost landed the lunar lander and aborted to see if it works was a waste of money. The might as well have landed the thing and would have had one lunar mission more to justify the expense of Apollo.

I think we should accept some risk. Even a successful colony would have some deaths occuring on Mars. People die on Earth, why shouldn't they also die in space and on Mars. The trick is to see to it that the deaths don't jeapordize the mission, and when missions fail, you just try to fix what is fixable and then you go on. People will die in space and on Mars, if we can't accept that then we shouldn't go there.

cIclops · 2007-11-21 01:25:40

I hope its not going to be generations! I hope to see an era of rapid progress like the early 20th century. Lets just perfect the technology for living on Mars and just go their. Mars is not the place for testing such technology for if it fails people die. Deterimine the reliabilty of the equipment before hand before sending any people. I think if we have until 2031, that is plenty of time to test the equipment, and by that time we should be ready to plant the first colony. We're not going to spend billions of dollars to go to Mars just to see if something works. That is basically my problem with the design reference mission as well, it doesn't use technology which could make it cheaper, it instead wastes billions of dollars going the cautious route until we can be sure we can produce propellent to fuel the return stage. I really don't think we need to be in the vicinity of Mars to test this equipment. I also think the Apollo 10 mission where they almost landed the lunar lander and aborted to see if it works was a waste of money. The might as well have landed the thing and would have had one lunar mission more to justify the expense of Apollo.
I think we should accept some risk. Even a successful colony would have some deaths occuring on Mars. People die on Earth, why shouldn't they also die in space and on Mars. The trick is to see to it that the deaths don't jeapordize the mission, and when missions fail, you just try to fix what is fixable and then you go on. People will die in space and on Mars, if we can't accept that then we shouldn't go there.

Generations of the transportation system, not people. Before Apollo there were two generations in the US system: Gemini and Mercury. After Apollo there was Shuttle and now Constellation. A Mars mission will require additional spacecraft (MTV, lander) and maybe a new inspace propulsion rocket (NTR). It seems unlikely that Mars colonists will be traveling in this generation of equipment.

2031 is a provisional, reference date for a Mars expedition, not a technical one. With enough funding it can be much sooner. If there's a better, cheaper technology fine, but so far there's no contenders. Going to the Moon is still at the edge of current technology, it will expensive and risky. There's more than enough risk already. Currently every crew that launch into space has about a 2% risk of dying. Ares I will reduce that risk by a factor of ten, but a lunar mission will still have about 5% risk, isn't that more than enough? Going to Mars will be more so.

Tom Kalbfus · 2007-11-21 12:21:21

No, it was out at the edge of current technology 40 years ago. I don't believe that all our experience with manned space travel counts for nothing since that time. I think if we are going to wait until 2031, our expectations ought to increase with that receding launch date. I don't think all technological innovation will be held in stasis while we wait for Congress to appropriate the necessary funds, and whats with this shying away from nuclear space propulsion systems? If we are going to wait until 2031, we'd surely have plenty of time to develop them. Do our nuclear engineers have any brains in their heads or what?

I think that if we wait until 2031, we will be advanced enough to start right in with colonization to make up for lost time and all of that useless pointless waiting. I'm starting to think people are deliberately delaying things and are doing the minimum necessary to get to Mars, same with the people who want to keep flying cars out of our skies, we've had the technology to build such for almost a decade now, yet all the officials at the Transportation Department are digging in their heels.

I really don't want the first manned landing on Mars in 2031, after much procrastination and deliberate delay, to be just another Apollo thing we watch on television, if it is, what's the point. I want it instead to be the beginning of something major, maybe the beginning of the real 21st century for instance when large numbers of humans move into space. Its really not that hard so long as we stop shying away from technologies that promise to get us there.

I've lived since 1967, I've watched technology progress until it edged closer to getting us into space and then it slowed down to a crawl with no one really wanting to go a little further. I also think they deliberately fumbled the National Aerospace Plane and the Venture Star, and then we moved in another sharply different direction, just so long as we waste the public's money without getting anywhere. I think the Shuttle was a diversion from going to Mars in the 1980s, I don't know what motivation was behind it though. It is just a sneaking suspicion of mine, everytime I see technology slow down when we edge closer to traveling in space. I don't know why its happening.

cIclops · 2007-11-21 12:36:57

No, it was out at the edge of current technology 40 years ago. I don't believe that all our experience with manned space travel counts for nothing since that time. I think if we are going to wait until 2031, our expectations ought to increase with that receding launch date. I don't think all technological innovation will be held in stasis while we wait for Congress to appropriate the necessary funds, and whats with this shying away from nuclear space propulsion systems? If we are going to wait until 2031, we'd surely have plenty of time to develop them.

Yes, going to the Moon was at the edge of technology 40 years and still is today. There's an old joke: "If we can go to the Moon, why can't we go to the Moon?"

All the experience with manned space travel since Apollo has been in LEO. Going back to the Moon has different challenges and is technically far more difficult. Unless NASA gets extra funding then it will be 2031 or later before they can send people to Mars, it may be much later if certain politicians get power. Of course ESA/Russia or China may do it sooner. Parlez-vous francaise?

Tom Kalbfus · 2007-11-21 18:27:33

No, it was out at the edge of current technology 40 years ago. I don't believe that all our experience with manned space travel counts for nothing since that time. I think if we are going to wait until 2031, our expectations ought to increase with that receding launch date. I don't think all technological innovation will be held in stasis while we wait for Congress to appropriate the necessary funds, and whats with this shying away from nuclear space propulsion systems? If we are going to wait until 2031, we'd surely have plenty of time to develop them.
Yes, going to the Moon was at the edge of technology 40 years and still is today. There's an old joke: "If we can go to the Moon, why can't we go to the Moon?"
All the experience with manned space travel since Apollo has been in LEO. Going back to the Moon has different challenges and is technically far more difficult. Unless NASA gets extra funding then it will be 2031 or later before they can send people to Mars, it may be much later if certain politicians get power. Of course ESA/Russia or China may do it sooner. Parlez-vous francaise?

In which case we can question those politician's patriotism for throwing the Moon/Mars race to foreign nations, and I intend to if it comes down to that, then I hope to get a snowball moving downhill out national outrage at the politicians who threw the race. I think 24 years is a joke. They already tested nuclear rocket engines in Jackass Flats in the 1960s and they worked, there is no reason not to use them in the Design Reference Mission, especially if we allow ourselves 24 years to do it, Now I'd understand if we tried to accomplish this in 8 years. If we set a target date of 8 years to land men on Mars, we'd want to use off the shelf technology, that would be Ares I and V rockets, an Orion Capsule, and a Hab and Earth Return Vehicle. There is nothing specific we need to accomplish on the Moon before going to Mars. I don't think we need to wait until all the Moon missions are all over before setting our sites on Mars and figuring out what to do. The current Administration and Congress have just one year left, by 2009, we'll have a fresh set of faces to convince, and perhaps we can convince them to step on the accelerator. We are already moving in the right direction, one half-step at a time, I think a good goal for us is to try to convince the next Administration and Congress to go full throttle to Mars and to try to get there before the end of the next two Presidential terms, that is the President who proposes it should be the one to see the project through to the first human foot prints on Mars.

cIclops · 2007-11-22 06:36:10

I think 24 years is a joke. They already tested in the 1960s and they worked, there is no reason not to use them in the Design Reference Mission, especially if we allow ourselves 24 years to do it, Now I'd understand if we tried to accomplish this in 8 years. If we set a target date of 8 years to land men on Mars, we'd want to use off the shelf technology, that would be Ares I and V rockets, an Orion Capsule, and a Hab and Earth Return Vehicle.

24 years is NASA's estimate given the current budget. If you want NASA to do it sooner either give them more funding or tell them to stop doing other things.

The Rover/NERVA nuclear rocket program had just started testing when it was canceled, an enormous amount of work would be required to make it operational, but yes it seems to work.

8 years is a very tight schedule, but not impossible provided no big problems appeared (crew health for example), but it would need a LOT of money, a doubling of the budget or more! The question that will be asked by everyone is, what's the rush?

Tom Kalbfus · 2007-11-22 07:53:27

No rush, that's 46 years after the Apollo 11 mission! I consider more than half a human lifetime to be no rush at all. NASA is after all an expert in putting things off. Anyway that is about how long it took us to get to the Moon, and I'm talking about launching the mission in 8 years, it will take a bit longer to actually reach Mars. What's there to do? Build 2 Ares V rockets, one Ares I rocket, those two rockets have equivalents in the Apollo program. We need to build a nuclear rocket stage, and were not exactly clueless on how to build such, we need a Hab, and an Earth Return Vehicle, and of course Mars Space suits and a rover. 8 years is plenty of time to build all that stuff. Its not like you have to wait until you've build the Ares I before you can start building the Ares V. Presidents have accomplished plenty of things in their two terms in office, World War II has been won in less that two Presidential terms.

I just think that if one President starts something, he ought to be around to finish it, it doesn't seem unreasonable for one Presidential Administration to accomplish a manned Mars program while still in office rather than having to hand it off to the next President. I get tired of this talk about "how many decades its going to take to get to Mars" Our planning horizon has extended too far. If we're going to talk about going to Mars, lets talk about doing it in a reasonable amount of time. That's what Zubrin's Mars Direct plan was all about.
yet everytime government gets its hands on it, they always try to spend more money on it, make it bigger, and make it take longer. I think its cheaper to build a NERVA stage than 4 more Ares V rockets.

cIclops · 2007-11-23 12:10:55

Perhaps DRM 5.0 and ideas from Spaceworks Engineering (SEI) can be combined with others to produce a less risky and more robust architecture. As with all space missions, mass is critical. Mars has one big advantage, propellant can be produced there by ISRU as described in Mars Direct (MD). Logically, only the propellant needed to get to Mars should be taken. That means ALL propellant for the return journey ought to be produced by ISRU as in MD. The problem then is how to support a more robust mission with six crew without having an overweight return vehicle on the surface of Mars.

Solution: split the ascent vehicle into two parts. One part to launch propellant to Low Mars Orbit (LMO), the other to launch the crew. They both dock with the Mars Transit Vehicle (MTV) and Orion waiting in LMO. The return stack was earlier aerobraked/aerocaputured into LMO.

Next, how to produce the propellant for both ascent vehicles?

Solution: a mobile ISRU! This comprises the ISRU plant and a surface nuclear power unit on a mobile platform. With nuclear power the range of the mobile ISRU is effectively unlimited, so it can dock with both ascent vehicles wherever they land, and later dock with the Hab to provide life support. Both ascent vehicles land with their H2 feedstock using standard cargo landers.

The cargo lander is also used for the Hab and the crew. When its tanks are refilled, the propellant ascent vehicle then docks with the return MTV stack. The return MTV is effectively a copy of the outward MTV, this reduces its mass by a factor of two. The crew travel to Mars in the outward MTV and a lander, this MTV is discarded just before EDL. The crew land with a long range rover, supplies for 30 days and a small lab. If they are unable to reach the Hab or have an emergency they can go straight to the fueled ascent vehicle. The rover can also be refueled by the ISRU plant.

Some numbers. SEI say that Ares V can deliver about 43 t to TMI, and a package this size can land about 20 t on the surface of Mars. The cargo lander has a mass of about 15 t. The ascent vehicles reuse these lander engines, tanks and structure. For crew a cabin is included, for propellant transfer, larger tanks. DRM 3.0 gives a mass of about 15 t for an ISRU and nuclear reactor so a mobile unit should be feasible. A Hab with 500 days of supplies has a mass of about 20 t. So these all fit nicely into single Ares V size packages with some spare mass enabling greater systems redundancy, more robustness and less risk.

Tom Kalbfus · 2007-11-23 13:10:58

One idea I thought up is a varient of the Ares V architecture where you replace the upper stage, that is the one which ferries the upper stack from Low Earth orbit to TLI and TMI, with a nuclear stage that takes up the same volume and mass budget. The fuel would be liquid hydrogen, and the engine a NERVA reactor, and suppose we made this design standard for all Ares heavy lift configurations. NERVAs are supposed to double the ISP of the chemical upper stages, they can fit inside the VAB, and sit on the launch pad just fine. Since were going to haul a nuclear reactor along anyway, why not one which can do some good in delivering added tonnage to LMO? Were talking about 24 years, at that leisurely pace, there is no excuse not te develop an nuclear rocket, so why not have an Ares N?

cIclops · 2007-11-23 14:10:27

One idea I thought up is a varient of the Ares V architecture where you replace the upper stage, that is the one which ferries the upper stack from Low Earth orbit to TLI and TMI, with a nuclear stage that takes up the same volume and mass budget.

The Ares V EDS upper stage is needed to reach LEO. Replacing this with a NERVA class engine would mean expelling radioactive exhaust into the stratosphere, a big NO NO.

Tom Kalbfus · 2007-11-23 16:17:49

The reaction mass is hydrogen. Radioactive hydrogen would be tritium, or deuterium. The Ares rocket should be over the Atlantic Ocean when the upperstage kicks in anyway.

cIclops · 2007-11-23 16:41:12

Yes, non radioactive hydrogen gas is used as the propellant, however in designs such as NERVA it flows through the reactor core so it transports radioactive particles. This radioactive exhaust would quickly circulate in the atmosphere and spread a long distance.

There are other designs which isolate the H2 gas from the core and that should eliminate this problem. Such an engine still needs a large hot reactor core, it will be very difficult to stop radioactive contamination if it falls to the ground. Better not to ignite it until it's safely in orbit, say 1000 kms up.

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#26 2007-11-19 09:49:37

Re: Design Reference Mission 5.0

#27 2007-11-19 10:37:05

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#28 2007-11-19 12:38:12

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#32 2007-11-19 17:47:07

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#33 2007-11-19 19:37:05

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#37 2007-11-20 13:50:50

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#39 2007-11-20 15:46:43

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