UK's Manned Mars mission Concept

[Paprika]

http://www.bbc.co.uk/news/science-environment-22952441

Just found this, any thoughts? I don't know as much about this stuff as a lot of you guys (hence me basically only posting in biology threads) so thought I'd steal a news article instead! mwahahaha

[Borklund]

Snap reaction:

Every part of this mission scenario has been demonstrated one way or the other, including the in situ propellant production on the surface of Mars," said Prof Tom Pike, who led the Imperial design team.

Tethers not proven tech

Artificial gravity not proven tech

ISRU not proven tech

ISRU prop production definitely not proven tech

The wording is peculiar; "demonstrated" to me means hardware built and tested but they may just mean demonstrated as in its viability has been demonstrated theoretically, in which case there remains substantial engineering challenges other than building a new iteration of existing and flight proven hardware, as with the more conventional parts of the mission proposal - the spacecraft and its subsystems, the conventional prop orbit craft and to a lesser extent the hab module. Besides the technological readiness, the merits of artificial gravity and ISRU prop production have not been proven. Sure, it would take a whole lot more mass (or a whole new launch with a robitic fuel depot lander in addition to the other elements) but then you wouldn't have as many unknowns and it would be a whole lot more viable.

This would create artificial gravity within the habitat vehicle similar to Earth's gravity, which the scientists believe would prevent the type of muscle and bone wastage that weightlessness would cause, which would render the astronauts unable to walk on Mars once they arrived.

It would render them unable to walk on Mars the moment they arrive, yes, but after a short period of acclimation and training they'd be able to walk again. Astronauts returning from the ISS walk within hours of returning to Earth.

"On its trip to Mars, it measured the radiation from these galactic cosmic rays and it was exposed to quite a lot - about two-thirds of the level that Nasa is prepared to risk over the whole of an astronaut's life, just on the way there and back again."

That limit is set at a 3% increased risk of contracting cancer after a lifetime's work. There's no reason why this goalpost can't or shouldn't be moved further to the right when it comes to exploring Mars, given what we've learned since that limit was established.

Edited July 25, 2013 by Borklund

[Nibb31]

Yes, it's an armchair concept. We come up with similar designs every day in KSP. There is nothing else backing it.

[3_bit]

This is pretty much Apollo with artificial gravity. Isn't that cable still a bit short at 60m, even if you're only generation .4 g's? Wouldn't you be going way over 2 RPM, and thus create some load problems?

[Winter Man]

Tethers not proven tech

Artificial gravity not proven tech

*ahem*

http://en.wikipedia.org/wiki/Gemini_11

[Borklund]

*ahem*

http://en.wikipedia.org/wiki/Gemini_11

47 year old short experiment which produced microgravity does not technologically ready make. What bearing does that have on a proposed Mars mission in the near future, which would be expected to generate 0.4-near 1g for 2x 9 months? It's physically possible, in theory, but that's not the same as proven technology that you can just start building without the need for substantial testing and demonstration.

Edited July 25, 2013 by Borklund

[Winter Man]

It means there's a precedent, rather than something they're just pulling out their arse.

[Nibb31]

The Gemini 11 experiment produced 0.00015g with a 30m tether. It also proved troublesome and showed that whole contraption was pretty risky.

Artificial gravity is not required for a 9 month transit. It just makes things complicated and adds a whole lot of very dangerous failure modes: what if the tether breaks? what if a thruster fails and you can't spin down the rotation or you send the counterweight crashing into the hab module?

It's a theoretical concept that is unnecessary and totally unproven.

[Winter Man]

I'm not saying it's a good idea, just that it isn't a fiction. We're better off waiting until decent centrifuge-based (no tether breaking here) habitats are up and running, like the one planned by Bigelow, than not using one at all. Muscular atrophy is not at all pleasant. Sure you can stick a load of treadmills in there, but the benefits of artificial gravity outweigh (ha!) the current technological drawbacks.

[Kerbface]

What about rather than a tether have a strong I-Beam or other sort of girder, or a set of metal poles, connecting habitat to lander. Obviously the downside is weight, the upside is sturdiness and more control.

[Borklund]

I'm not saying it's a good idea, just that it isn't a fiction. We're better off waiting until decent centrifuge-based (no tether breaking here) habitats are up and running, like the one planned by Bigelow, than not using one at all. Muscular atrophy is not at all pleasant. Sure you can stick a load of treadmills in there, but the benefits of artificial gravity outweigh (ha!) the current technological drawbacks.

[citation needed]

One person in the history of mankind has experienced artificial microgravity, not much different from what astronauts on the ISS experience, for a few short moments, 47 years ago. Compare to muscle and bone less which occurs naturally on Earth; we know infinitely more about muscle and bone loss mitigation and treatment than artificial gravity.

What about rather than a tether have a strong I-Beam or other sort of girder, or a set of metal poles, connecting habitat to lander. Obviously the downside is weight, the upside is sturdiness and more control.

Again, when has it been proven that artificial gravity is a necessity or even that it offers a benefit over spending the trip to and fro in weightlessness? Astronauts walk within hours of returning to Earth and with physical therapy normal functionality is restored within weeks, months (differs from person to person). There's nothing that says astronauts couldn't do this on Mars, especially not considering the longer stays on the surface (500 days in some scenarios).

[Thaniel]

I'm not overly entusiastic about their truss sollution either. I don't realy doubt it will work, but properly controlling something like that, or the risk of sudden unplanned entanglement or deconstruction just seem too high.

However, that said, while the inflatable donut construction is still a bit away, how about something that have been true and tested for quite a while, extendable wheel. I'm thinking something along the line of the hoberman sphere as a mechanical girder. The parts that makes up the ship is mounted along the wheel for even weight distribution, extendable trusses make up the spokes for support and for holding a central maneuver module in place. When they get to mars, they just collapse the wheel in a controlled fashion, and land.

True, such a construction would be heavier than just a cable connection, but, it would be much lighter than a completely built and pressurised ring, and it should be both reusable if built properly, be possible to reurpose as a station, if it have some sort pf standardised clamps or connections, different modules could be mounted on it, possibly making it possible to at some time pressurise a whole wheel on it or something. But the best thing, it can be built in pieces and assembled in LEO. And using tubes or other beneficial profiled materials, it should be relatively light, and it would function like a wheel proper.

[ZeroTheAstronaut]

From that article, I see little if no fundamental difference from Mars direct.

http://www.marssociety.org/home/about/mars-direct

ISRU...Check

Tethered Artificial gravity...Check

Hab/Lander...Check

[Pinkieseb]

It sounds so far-off, I think they'll push to get it done in the next few nears. Although they are saying everything is "demonstrated" How did they demonstrate it? Throw some astronauts into a radiation storm? You cant just "demonstrate" things to this extreame, But i still think they'll do it and make it.

[DerekL1963]

Although they are saying everything is "demonstrated" How did they demonstrate it?

Mostly on a lab bench or computer simulations - I.E. not demonstrated at all for all practical purposes.

[what-the]

Just tie down an astronaut to the inside of a washing machine and let them sleep in it. That other way will cost far too much if it's even possible.

[K^2]

What about rather than a tether have a strong I-Beam or other sort of girder, or a set of metal poles, connecting habitat to lander. Obviously the downside is weight, the upside is sturdiness and more control.

I have a feeling people here don't appreciate how long the tether has to be. Research done so far suggests that the angular velocity should not exceed 2rpm in the long term. From center of mass, that's over 22m of tether or other support for every .1G. If you want to have at least 0.5G on board of a rigid ship your ship is going to be longer than ISS.

The advantage of the tether is that it can be extended and contracted in flight. With a rigid structure, you will have to build your ship in Earth's orbit, then navigate that long, clumsy thing to Mars, do the mission, and on the return trip, transfer the crew from the Mars lander to command module on the orbiter. Compared to that, tether seems safe, and that's saying something.

Whenever we get to the point where we have routine missions to Mars, we'll have to figure out how to do this reliably and safely. But for the first few missions, there is really no good reason for this. There are enough things that can go wrong with a mission to Mars. Why add one more such thing?

Personally, I'd do the mission to Mars in the following manner.

1) Living module with supplies is delivered to LEO without a crew.

2) Mars lander is delivered to LEO without a crew.

3) Command module and interplanetary rocket is delivered to LEO with the crew.

4) CM docks with living module.

5) Living module docks with lander.

6) Burn from LEO to escape and establish transfer orbit.

7) Burn to establish low Mars orbit.

8) Lander separates from living module and lands on the surface of the Red planet with the crew.

9) Lander takes off and returns to Mars orbit to dock.

10) Lander is abandoned and the rest of the ship performs a burn to leave Mars and enter transfer to Earth.

11) CM separates from the rest of the ship and re-enters the atmosphere. The rest of the ship crashes somewhere in the ocean.

There are several advantages to staging mission like this. You deliver the ship to orbit in manageable chunks, but without significant risk of stranding the crew in orbit without means of re-entering. You also don't waste fuel on things you don't have to carry with you. A spacious living module is necessary for both legs of the trip, but there is no need to haul the lander back from Mars. Likewise, there is absolutely no need to make the living module capable of surviving re-entry. A small command module can carry the crew safely back to Earth.

The only place I can think of where significant fuel savings can be made is if lander separates from living module still on approach to Mars and does direct entry while the orbiter establishes orbit. But this seems like an increased risk to the mission.

Edit: I should do some estimates on the actual requirements for this mission. I'll be back with some numbers a bit later.

Edited July 26, 2013 by K^2

[metaphor]

It doesn't seem to me that zero gravity is that big of a problem, especially not one big enough to trust the whole mission to an untested technology.

Astronauts spend 6 months on the ISS and experience little to no bone loss with adequate exercise. If the deep-space habitat had an exercise machine inside it, the trip to Mars would really not be much different from the stays on the ISS (about the same length). Also, landing on Mars is much less stressful on the human body than landing on Earth. The deceleration for a Mars landing is only about 2 g's as opposed to the 5 g's for an Earth re-entry. And the surface gravity on Mars is only 37% that on Earth. So the astronauts probably wouldn't need more than a few days to adjust to Mars gravity, which can be spared out of a 600-day stay.

[K^2]

Why a 600 day stay? The first return window is less than a year from arrival. I really can't think of any reason to make the first mission any longer than necessary.

[NGTOne]

Why a 600 day stay? The first return window is less than a year from arrival. I really can't think of any reason to make the first mission any longer than necessary.

I think it's mostly because they can, and to get as much science done as possible.

Never underestimate the power of "because we can" - in 1960, they were nowhere near having the technologies and methodologies for a Moon landing ready, and yet they said they would do it by end-of-decade. We all know what happens next...

[sojourner]

like the one planned by Bigelow,

First I've heard of Bigelow working on this, last I read all he was working on was inflatable habs, got a link?

[K^2]

I think it's mostly because they can, and to get as much science done as possible.

Never underestimate the power of "because we can" - in 1960, they were nowhere near having the technologies and methodologies for a Moon landing ready, and yet they said they would do it by end-of-decade. We all know what happens next...

And yet Apollo 11 had only a brief period on the Moon, with much longer Lunar operations conducted by consequent missions. There is "because we can," and then there is building up to that gradually, as NASA has learned from the Apollo 1 incident.

We can do longer missions. But it doesn't mean that we should be trying to do everything at once in one go. That makes a disaster that much more likely. First mission should be designed for a bare minimum. And it's not like the months of stay that the minimum duration mission requires are not enough to get a lot of work done. Once we have men working up there, we are certain to learn how to make the consequent missions safer and more reliable, allowing for future missions to be designed with a longer stay. We can bring in more equipment and supplies that are really needed and less stuff that turns out to be relatively useless.

And yes, we should be planning for multiple missions from the start. There is a very real chance of the crew getting stranded on the planet, in particular, due to weather. Until we can know for sure that the lander can survive Martian weather for a an extended periods of time, we need to be ready to cut any mission short or to send a recovery mission.

P.S. I think Orion would serve well as the Command Module for the mission. I'm going to go with that for the estimates. I'll also see if some of the ISS modules can be used for the living module. Lander and rocket will have to be built from scratch, but I'll try to use the existing engines.

Edited July 26, 2013 by K^2

[metaphor]

Why a 600 day stay? The first return window is less than a year from arrival. I really can't think of any reason to make the first mission any longer than necessary.

Because that's how long an conjunction-class mission takes.

There are two kinds of missions to Mars: opposition-class and conjunction-class.

Opposition-class missions are where you take a relatively slow transit to Mars, stay at Mars only about 30 days, and then a long return to Earth while passing close to Venus's orbit. Something like this (the Venus flyby shaves a few days off but isn't needed):

It has the advantage of a shorter (~600 days) total trip duration, but the disadvantage of a very short stay on Mars, more time in interplanetary space, and more delta-v needed. Opposition-class missions use pretty much the same trajectory as a Mars free-return (like Dennis Tito's mission) except with a short stay at Mars instead of a flyby.

The other kind is the Conjunction-class, where you take a fast transit to Mars, a long stay at Mars of about 600 days, and then a fast return to Earth. Something like this:

It has the advantage of little time in interplanetary space, less delta-v needed, and more exploration time, but the disadvantage of a longer total duration (~900 days).

Conjunction-class human missions usually have faster than Hohmann transfer orbits in order to cut down the time needed to stay in interplanetary space. But you can always use a Hohmann orbit to save a little delta-v at the cost of increased travel time. Something like this:

That one has a shorter stay at Mars but longer transit times. The total mission duration is about the same though. Since staying on Mars's surface is preferable to staying in deep-space (lower radiation dose, no zero-g problems), Hohmann transfer conjunction-class missions are not used for crew transfers. But if you can split the mission into cargo and crew, you can send the cargo on a Hohmann transfer minimum delta-v trajectory, and then send the crew later on a fast transit trajectory.

[K^2]

Ok, I see what you meant. I did not even consider anything but a Hohmann transfer because it's absolute madness to do what you are describing as Conjuction-class as the first mission. It has a huge list of disadvantages. Timing requirements are stricter. The delta-V on both departure and arrival are much higher. This means significantly more fuel needed for the mission and much smaller margin for error, which increases risk to the mission, especially on Mars arrival, where you'll have to kill the delta-V just right or either smash into the Red planet or end up completely screwed in interplanetary space. The launch windows are also much smaller. You can miss the Hohmann transfer window by as much as a month on the return trip without that much extra delta-V requirement. And then there is duration. The 30-60 day mission can be done with a very light lander. A 600 day mission will not even be able to land as a single lander. You'll have to drop the supplies separately and that's an entire list of additional risks.

And the only real advantage for the first mission is shorter transit time. If the duration of Hohmann transfer was prohibitively long, then yes, I understand the rush. But it's not. We can keep astronauts healthy for 300+ days in microgravity. Russians have done over 400 days on Mir. Even with the stay on Mars being as short as it is, this isn't as much of a limiting factor as all of the issues above. Even if problems develop, they will not be mission-critical, and certainly no the sort of stuff to endanger the entire crew.

No, absolutely not. Opposition launch is the only way to go for early missions. Once we have something up there to provide a safety net, we can start doing these faster, riskier missions.

[NGTOne]

Ok, I see what you meant. I did not even consider anything but a Hohmann transfer because it's absolute madness to do what you are describing as Conjuction-class as the first mission. It has a huge list of disadvantages. Timing requirements are stricter. The delta-V on both departure and arrival are much higher. This means significantly more fuel needed for the mission and much smaller margin for error, which increases risk to the mission, especially on Mars arrival, where you'll have to kill the delta-V just right or either smash into the Red planet or end up completely screwed in interplanetary space. The launch windows are also much smaller. You can miss the Hohmann transfer window by as much as a month on the return trip without that much extra delta-V requirement. And then there is duration. The 30-60 day mission can be done with a very light lander. A 600 day mission will not even be able to land as a single lander. You'll have to drop the supplies separately and that's an entire list of additional risks.

And the only real advantage for the first mission is shorter transit time. If the duration of Hohmann transfer was prohibitively long, then yes, I understand the rush. But it's not. We can keep astronauts healthy for 300+ days in microgravity. Russians have done over 400 days on Mir. Even with the stay on Mars being as short as it is, this isn't as much of a limiting factor as all of the issues above. Even if problems develop, they will not be mission-critical, and certainly no the sort of stuff to endanger the entire crew.

No, absolutely not. Opposition launch is the only way to go for early missions. Once we have something up there to provide a safety net, we can start doing these faster, riskier missions.

Micrograv is one thing. Radiation is quite another. Mir and the ISS both orbit inside Earth's magnetosphere, whereas your prospective Mars mission would be in interplanetary space, fully exposed to solar radiation (Curiosity's radiation instrument was running the whole way to Mars, and measured that the total radiation exposure on the way there was something like 2/3 NASA's maximum lifetime dose for astronauts, ONE WAY - meaning that one mission would put you over the limit by as much as 30%). Thus, it stands to reason that shorter transfer times are desirable, especially given that a longer stay on Mars would have large scientific benefits (for instance, serving as an ongoing experiment in long-term variable-gravity biology - we only have experience in 1G or 0G, and nothing in between; a 600-day Mars mission would basically be the test case for low-G human health studies).