I know, its called a 'Venus fryby'.
The fact that such a scheme is seriously considered (mainly by the Russians) just shows how difficult and expensive it is to stay on mars for 500 days.
On the first time you go there!

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Why bring them back? Resupply missions would be cheaper, especially if they find Martian water and don't have to send more. Bringing back astronauts and sending more later would cost a lot more then sending resupply missions. If future administrations want to bring back the survivors later when technological advancements bring down the cost they can do so then. There's no need for us to plan for that.

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Actually Cugel, what appears to the disadvantage of human missions, 540 surface stay and the need to return, are advantages. The cost of human missions means that exploration opportunities should be maximised. This pushes towards the long stay conjunction class missions as opposed to short stay opposition or sprint missions. A goal of Mars exploration is sample return. You can either bring them back in 100 gram lots with a robot, or 100 kg lots with a crewed mission, the human mission has the advantage the samples will be better selected and described than by a robotic mission, plus the people doing the sampling can work on them for
the rest of their professional lives.

Science and exploration are the main drivers for exploring Mars. There are no economic or militarily reasons, the political payoff is not there given the long lead times.

As to mission modes, the aptly named “Venus fryby” was largely considered by the US, not the Russians. Most US mission proposals until the 90’s were opposition type, generally with Venus flyby. The only Russian mission to have this was the ~1965 MAVR which was a combined Mars-Venus flyby (no landing). All others were either conjunction (MPK 1956, MEK 1960), sprint (Keldysh missions of 1994 and 2002), or opposition with electric propulsion and no Venus flyby (MEK 1969, Mars 1986, 1988, 1999, Marspost) mission profiles.

The only advantage of opposition missions over conjunction type missions is that they have a slightly shorter mission profile. This allows a reduction in mission mass if you bring all your consumables from earth. If you use local resources you to drastically cut the consumables brought from earth making a conjunction mission significantly lower mass. Conjunction missions also have the shortest exposure to the riskiest part of the journey (apart from landing and launch), which is interplanetary space, and the maximum exploration time. With in situ resources you can have a 4 person Mars mission for an earth escape mass of ~140 tonnes, three launches of a Saturn V class booster.

For comparison, for this same mass you could launch 17 MSLs. These, over many years, might cover the territory the human crew could explore in a few weeks.

More generally, another issue not often considered is that, if the crews return to the same base, infrastructure can be built up that
results in geometric increases in capability. Despite a lot of arm waving about "robotic villages", this is very difficult to achieve with
robotic missions, which leaves a long term robotic program consisting of scattered pin pricks across the planet. This is what we
have now, and it is OK for a start, but is not sufficient for a detailed understanding of the planet. If we want a detailed understanding
then people will go. If all we want is pinpricks, then viva robotica!


Jon

How about getting some lifers from prison and sending them to set up a colony. Sort of like how Australia got started. I think if I was rotting away in a cell I'd rather take a trip to Mars.

"Good news, we're letting you go. Bad news, we're letting you go to Mars."

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Hi Jon,

From a scientific point of view, I have to agree.

We agree on this one too. My point is that the US (nor any other nation) is willing to spend 40+ billion on a single science project.

Actually, these Zubrin numbers are extremely optimistic. Understandingly, he didn't exactly focus on the hard parts of the mission. Landing with a parachute (as an example) is not an option for a crewed vehicle. It takes a lot of fuel and hardware to safely hover and land humans on Mars. You can't say "let's send two crewed missions, if we're lucky one will survive". By the way, we don't have Saturn-V class boosters, these days.

This one, I do not agree. With 17 different landing spots it is my opinion that more Mars territory will be covered. It also spreads the risk, if one mission fails you still have 16 left! Personally I think the territory covered by humans is rather restricted. You need a pressurised rover, which is heavy and thus costly and Mars does not have highways. Safety precautions will probably prescribe that the crew must be able to walk back to base in case the rover is disabled. A radius of 10 miles seems more reasonable to me.

Yes, that is true. I think robotic missions are indeed of the type: learn and leave. I mean, why would we hang around on Mars? There are many more interesting places in the Solar system. But of course, if your long term goal is to establish a permanent human presence on Mars it is a completely different story. Maybe this is where our opinions actually differ?

Regards,

Henk.

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I'm still holding hope for a 30 year window. But I don't see NASA or another nation (except China *chew TUMS*) pulling it off. I'm hoping for an explosion in commercial space development. If private space takes off (pun alert), it could possibly happen. The money is there, they just need the technology base to make it fly. The next ten years for private aerospace industry will go a long way in how far they can go in the following 20.

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There were some early Moon mission designs based on similar notions.

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That's a whole different ballgame. You're no longer talking about explorers, but colonists. Drawing on US history and adding a touch of modern attitudes, how do you think the world would respond to a colony that ended up like Roanoke? Whether you think it fortunate or not, this isn't the 16th century, colonial success or failure isn't something that just concerns the colonists, not with modern attitudes like they are. Colonies in space or on the moon almost certainly will require massive logistical support to sustain them. The idea of putting a group of people on another planet and forgetting about them, whether that's what the colonists want or not, just isn't in the cards. Too many activist busy-bodies, not enough people shooting them.

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*ahem* >prisoners< I'm serious, why not? What else are we going to do with lifers and what else are they going to do but rot in jail? Rehabilitate them? For what, they are never getting out. I think a few would volunteer. Never hurts to ask, then when we have enough volunteers that nobody is too worried about we can skip a few test flights and just go for it. Why not? They volunteered.

I think it could work and if not, pfft. It would make a good script for a movie at least. The Dirty Dozen meets space travel.

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Reference on how to (ok it's the moon and it's fiction, but a great book)

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Heh, yeah, great Hollywood, but in reality, the ACLU and a few other alphabet soup organizations would have a field day crucifying anyone crazy enough to suggest this publicly.

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I'm not completely heartless, the doctor who removed it told me he'd never be able to get it all.

I think it will take longer. Mars is a big place, with a complex history, so it would be a long time until rovers and autonomous aircraft could explore large parts of it. Also, robotics is advancing fast, and in a few years the capabilities will greatly increase (compare the current rovers to Pathfinder, for example) leading to new improved missions with no end to the potential in sight. And, lastly, with a launch window only every other year, and budget for only a couple of missions per window, it will take a long time to launch dozens of robotic missions to Mars.

Mars is not Australia. Convicts transported to Australia were, for the most part, from rural, domestic, and trade backgrounds with skills that were useful in a settlements that required both types of labour.

Modern convicts in all societies are mostly poorly educated, with poor literary, numeracy and technical skills. Many suffer from high levels of mental illness, and are socially dysfunctional. Do people really think that these are skills needed to establish a Mars settlement?

Convicts were attractive for Australia because they provided cheap labour, transportation costs were low. Cheap labour will not be needed on Mars and transport costs are astronomical.

Jon

Hi Henk

Agreement or near so in many areas. Focusing on the few areas of difference:

Shuttle, ISS, Aurora say otherwise. Remember this cost is cumulative, not upfront
Actually, these are not Robert's numbers, they are mine (in part). See forthcoming paper in JBIS, accepted last week. It is a Mars semi direct, not direct mission profile. Hence three spacecraft, not two (crew lab, logistics module with ascent stage, Mars transfer vehicle. But I digress. Parachutes can be used to slow the spacecraft from low supersonic to 100 seconds before landing. We calculate 100 seconds of fuel is all that is needed. No helicopter-like flying across the Martian surface you would fly down a homing beacon. Most proposed manned Mars landers have used this method. Bummer about the Saturn Vs isn't it? We use a launcher of this class for convienence, but its lack is not a show stopper. It is technically feasible, though probably impractical to assemble an MD a mission using Delta IV class launchers. Our mission would require a 50 tonne minimum payload for orbital assembly given the design of the landing modules.


We don't know how long MSL will last of course, so we are guessing. Nor do we know how fast they will move - more guessing. But if we assume they last as long as the Vikings (V1 passed 6 years) and cover as much ground per year as Spirit - 4 km (MSL will probably move faster but spend longer on site with more than twice the experiments), they should cover 24 km apiece. For 17 missions this is 400 km. The LRVs averaged 10 km per EVA, that is 40 EVAs, 10 weeks max assuming 4 EVAs per week, which is reasonable, I think. On Mars longer traverses, up to 20 km per day should be possible even with an unpressurised rover, with experience and the higher gravity. Remember the 10 km limit is the walk back distance, the actual traverse can be a great deal longer. However a Mars mission will don't simply have a LRV style rover, it will (or should) have a pressurised one which can travel for 100's of km, with a radius limited by the recovery capability (40 km if the unpressurised rover stays at base, 100 km if it accompanies the pressurised rover. Longer ranged mission would require either two rovers (hence the importance of building up infrastructure) or establishing of supply caches.

Redundancy is a good point. However, realistically a crewed mission will have so much redundancy plus self repair that the only likely catstrophic failure modes are those during launch and entry.

I suppose it depends on your interests what you find interesting. I am for humans on Mars (and the moon) because I am a geologist with a secondary background in biology. My experience tells me that direct human presence is the best way to explore. Because these two bodies are the easiest for human's to access then I think it is important to do it. But Idon't think that everything else should stop for the moon or mars, and I don't think this will happen. People on the moon and mars, and robots goign further in and out. Permanant settlement is a different kettle of fish. I can see Mars an Antarctica in the sky, beyond that who knows?

Cheers

Jon
Regards,

Henk.[/quote]

ToSeek:

Do you have any references for this? I'd be interested in following up.

- http://www.hq.nasa.gov/office/pao/Hi...205/ch3-2.html

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Thanks!

As one who grew up post-Apollo, I find it easy to think that the way that they did things was the only way they could have done them. It sounds like there was pretty heated politicking going on about the best way to devise the mission.

(But I was glad to read that NASA never seriously considered the one-way option!)