Going to Mars

[MegaFlop10]

I was doing a little bit of research to see what the CSM/LM on an SLS would do.

I found that the LM's (Landing AND Ascent stage) delta V was 4,690 m/s, and this says the delta V for Mars orbit is about 3.8 km/s.

I calculated the delta V for the SLS Stage 2, with a CSM and LM on it, to be about 9,342 m/s. The delta V from LEO to LMO is about 10 km/s.

The empty weight of the Stage 2 and CSM/LM is 130,298 kg, and funnily enough, the SLS payload to LEO is 130 tonnes.

I can't wait for a manned Mars landing.

[Nibb31]

Only a couple of minor flaws:

- You omitted the dV to land a fully fueled LM on the surface.

- Once the LM gets back to LMO, then what?

- The CSM/LM only had consumables for a couple of days.

- There are no more Apollo CSMs or LMs.

[KerikBalm]

"- You omitted the dV to land a fully fueled LM on the surface."

He probably assumed its something like duna and stock aerodynamics, where you just pop chutes, and fire off about 10 m/s worth of dV to cusion the landing....

Aerobraking would save a lot of dV, (in theory at least 3.8 km/s), but that requires a heat shield, which is going to reduce the dV of the stage going to mars.

And even so... Mars' atmosphere is really really thin... you'll still becoming in very fast even with chutes (which again add weight), and you'll probably need a dV of another few hundred m/s.

For reference, the pathfinder mission, which was a small payload (the type you want if you want to land on just parachutes)... was coming in at 68 m/s - it would be even worse for a heavier craft. Then you need to figure in the gravity drag while firing the retrorockets...

Its not all that much... the biggest problem is the consumables for the journey, and that you really want to be able to get your astronauts BACK to Earth.

NERVA, we need NERVA (or prometheus nuclear-electric drives, ideally both)

[Brethern]

"- You omitted the dV to land a fully fueled LM on the surface."

He probably assumed its something like duna and stock aerodynamics, where you just pop chutes, and fire off about 10 m/s worth of dV to cusion the landing....

Aerobraking would save a lot of dV, (in theory at least 3.8 km/s), but that requires a heat shield, which is going to reduce the dV of the stage going to mars.

And even so... Mars' atmosphere is really really thin... you'll still becoming in very fast even with chutes (which again add weight), and you'll probably need a dV of another few hundred m/s.

For reference, the pathfinder mission, which was a small payload (the type you want if you want to land on just parachutes)... was coming in at 68 m/s - it would be even worse for a heavier craft. Then you need to figure in the gravity drag while firing the retrorockets...

Its not all that much... the biggest problem is the consumables for the journey, and that you really want to be able to get your astronauts BACK to Earth.

NERVA, we need NERVA (or prometheus nuclear-electric drives, ideally both)

The biggest problem would probably be comfort imagine being stuck in that capsule for a year with no real lavatory.

[MegaFlop10]

I forgot about all that. Thanks anyways, I learned quite a bit. I wonder how the space agencies would find a way around all these problems, they seem really difficult.

[meve12]

NERVA, we need NERVA (or prometheus nuclear-electric drives, ideally both)

Would solar-electric do, or does it have to be nuclear? Because we have working designs for sufficiently large solar panels, and none for zero-g reactors, as far as I know.

[meve12]

More on topic: If the CSM is moved to a different flight, how much deltaV would the lander/booster have? You'll need enough to mount a Mars descent stage(heat-shield, parachutes, retrorockets...)

And how big/heavy do Transhabs get these days? Because you'll need some more leg room.

- - - Updated - - -

More on topic: If the CSM is moved to a different flight, how much deltaV would the lander/booster have? You'll need enough to mount a Mars descent stage(heat-shield, parachutes, retrorockets...)

And how big/heavy do Transhabs get these days? Because you'll need some more leg room.

- - - Updated - - -

More on topic: If the CSM is moved to a different flight, how much deltaV would the lander/booster have? You'll need enough to mount a Mars descent stage(heat-shield, parachutes, retrorockets...)

And how big/heavy do Transhabs get these days? Because you'll need some more leg room.

[K^2]

So basically, this is enough delta-V for a one-way mission, including a soft landing. A horribly depressing, barely survivable mission with no way to return. And I'm sure enough people would still volunteer to require a selection process.

Would solar-electric do, or does it have to be nuclear? Because we have working designs for sufficiently large solar panels, and none for zero-g reactors, as far as I know.

For interplanetary, yeah. It'd be a very low thrust engine, but I_SP of an electrothermal can be just as good as that of NTR, and you have nothing but time with a mission like that.

That said, wasn't NERVA designed to operate in zero-G?

[rtxoff]

I forgot about all that. Thanks anyways, I learned quite a bit. I wonder how the space agencies would find a way around all these problems, they seem really difficult.

They will probably need multiple launches and build the spaceship in Orbit. However, who is going to pay such an mission?

[KerikBalm]

There are plenty of designs for operating a reactor in zero-G.

http://en.wikipedia.org/wiki/SNAP-10A dating back to the 60's, even before the "flight ready" NERVA designs.

The larger the solar panel, the more mass it is, you simply can't get good acceleration from a solar powered propulson system without lowering your ISP to horrible, horrible levels.

There is a reason the Dawn probe (solar powered propulsion) took 4 years to reach Vesta... A hohman transfer would only take 6 months or so... but it didn't have the acceleration required to do such a maneuver.

[peadar1987]

They will probably need multiple launches and build the spaceship in Orbit. However, who is going to pay such an mission?

It's a pity nations won't work together on this. If we had, say, a Russian launcher, Chinese transfer stage, European habitation module and American lander, and an Indian power supply*, the costs would be a whole lot more manageable for any one nation.

*I know in reality collaboration wouldn't be quite so Kerbal-like as this!

[KerikBalm]

Another thing... that lunar lander was super flimsy... it would not survive martian reentry (fine, encase it in a fairing+ heat shield, adding a lot of weight), and I'm not sure about ascent when its going that fast (sure, mars' atmosphere is thin though...). But you'd also have to increase its engine size, since it was meant for lunar grav, not martian gravity.

I think we first need to establish the weight of the hab modules(+supplies) you'd need for the journey to mars.

Getting something to mars isn't the hard part... its getting something that can sustain humans for 2 years without resupply that is the hard part.

The ISS doesn't go that long without resupply...

Compare the lunar lander with what you would need for mars... you can't have them sit in that thing for 6 months, or just do a 2 day stint, and then go back to orbit and wait months for the return transfer window.

If what you need to land is 100x as heavy, then a single launch is going to end up being many, many many times as expensive as the apollo program

[MegaFlop10]

I wasn't seriously suggesting having a CSM/LM around Mars, but more like a modified version or heavy version. I was probably too vague.

But I still really appreciate all your comments, and now I realise how silly I was.

At this point I'm actually a bit doubtful that any manned landing will happen at all.

[Seret]

At this point I'm actually a bit doubtful that any manned landing will happen at all.

It probably will eventually, but not without significant advances in propulsion and life support. In the meantime our robots will be down there diligently exploring and getting more effective.

[peadar1987]

It probably will eventually, but not without significant advances in propulsion and life support. In the meantime our robots will be down there diligently exploring and getting more effective.

Hmm... I don't think the advances would even have to be that significant. We could probably do it with today's technology, or at least with SLS when it comes out. I wouldn't count NERVA as a hugely significant advance either. It was pretty much ready to go 40 years ago. Launch a few modules separately, dock them in orbit, carry enough supplies to remain independent of earth. NASA estimate that each astronaut would need about 2000kg of food for a 1000 day Mars mission. That's 8 tonnes for a crew of 4. It's big, but not insurmountable. We can reprocess water and air without too much of a problem, we just have to make sure we include enough spares to keep the system running.

[Mr Shifty]

Stephen Baxter's novel Voyage imagines an alternate history with a Mars mission in the 80's using Apollo hardware. The novel is excellent, and well worth the read for any KSP player; it's got nuclear engines, rocket explosions, orbital assembly, realistic orbital mechanics etc etc. They use a modified Saturn V with SRBs to launch the Mars vessel into orbit. The transport vehicle has to be assembled over several launches, and they use wet workshops for the habitats. An enterprising soul created an add-on for Orbiter with all of the vehicles in it, then someone else made a fantastic video show-casing the whole mission:

[Seret]

Hmm... I don't think the advances would even have to be that significant. We could probably do it with today's technology

Not at an acceptable level of cost and risk.

[peadar1987]

Not at an acceptable level of cost and risk.

Really? What advances do you think we'll need before a Mars mission is feasible?

edit: Reading that back, it sounds a bit belligerent. That's not how it was meant, but I can't think of a way to rephrase it. I'm just curious about what other people who might know more than I do think.

[Seret]

Really? What advances do you think we'll need before a Mars mission is feasible?

All or most of:

• Faster, more efficient propulsion.
  
• Substantially reduced cost to Earth orbit.
  
• Closed cycle life support that was reliable over multi-year long missions.
  
• ISRU.
  
• More experience with mitigating the effects of long-duration low-g and high-radiation.
  

[peadar1987]

All or most of:

• Faster, more efficient propulsion.
  
• Substantially reduced cost to Earth orbit.
  
• Closed cycle life support that was reliable over multi-year long missions.
  
• ISRU.
  
• More experience with mitigating the effects of long-duration low-g and high-radiation.
  

Okay, I agree with you on most of them (and learned how to make lists ). Would you agree that if we really had to go to Mars within ten years, we could almost definitely pull off a credible mission, albeit a very expensive one?

What would be your first step for a manned Mars mission?

I think you're right on needing more experience with the effects of low-g (although we have plenty of experience with the effects of radiation. We know the dose astronauts are likely to get, and we know the increased risk of problems that's likely to cause). First move for me would be to build a tethered system in earth orbit that could be spun up to simulate various levels of gravity, even to simulate an entire mission to Mars. At the same time, various life support systems could be trialed, to see which is the most reliable, and most effective.

[meve12]

There are plenty of designs for operating a reactor in zero-G.

http://en.wikipedia.org/wiki/SNAP-10A dating back to the 60's, even before the "flight ready" NERVA designs.

The larger the solar panel, the more mass it is, you simply can't get good acceleration from a solar powered propulson system without lowering your ISP to horrible, horrible levels.

There is a reason the Dawn probe (solar powered propulsion) took 4 years to reach Vesta... A hohman transfer would only take 6 months or so... but it didn't have the acceleration required to do such a maneuver.

Oh, Ok. Musta missed that.

Now all we have to do is sneak it past the Partial Test Ban.

All or most of:

• Faster, more efficient propulsion.
  
• Substantially reduced cost to Earth orbit.
  
• Closed cycle life support that was reliable over multi-year long missions.
  
• ISRU.
  
• More experience with mitigating the effects of long-duration low-g and high-radiation.
  

To tackle those in reverse order:

5. The ISS is already helping with that.

4. Point taken.

3. The ISS is also testing components for these, I think.

2. ...Darn it all, that is our bottleneck at the moment, isn't it?

1. Lots of choices for this. Certainly ion and plasma engines have been used on probes, not a stretch to think we'd upscale them for a manned Mars mission.

0. Liftoff!

[Seret]

Would you agree that if we really had to go to Mars within ten years, we could almost definitely pull off a credible mission, albeit a very expensive one?

I think we could launch a very expensive one, with a pretty unpalatable chance of success. Even Apollo was far from definite, they were lucky not to lose anyone and the moon is a much, much easier trip than Mars. To bring the risk down to acceptable levels would require a huge amount of investment, research and development. This would take an incremental approach, with numerous unmanned missions preceding the final manned shot. You wouldn't get much of that done in only ten years.

What would be your first step for a manned Mars mission?

Closed loop life support is probably the most important one that we stand a chance of making some good progress on. It's an extremely complex problem, but we'd be able to construct the labs to test it on Earth and in Earth orbit, so it's potentially doable. We understand a fair bit of what's required and have some good ideas about how to do it. If we seriously ramped up our testing programme I'd expect to see some good results.

ISRU experiments can be done unmanned, IIRC the next Mars rover will have one on board, so we could get on with that. We're still very much at the bottom of that learning curve though.

[MegaFlop10]

I have another idea.

Maybe an unmanned ship with food and resources can go to Mars orbit first and maybe even with a return module, then the manned ship will rendezvous with the first one so that the weight and resources aren't too much for a single ship.

[Seret]

That's actually a mission architecture proposed by a lot of studies. A lot of proposals include sending the return vehicle out first with enough fuel to land and having it manufacture the fuel for the return journey on Mars. Once that ship confirms that the tanks are full the crew are sent out.

A mission as big as a manned one to Mars pretty much necessitates multiple launches over more than one launch window.

[Guest]

That's the basic idea behind Copernicus. It'd be a 7-launch Mars return mission, with unmanned flight of two ships first, to set up a robotic base on Mars, then a manned flight and landing. Return would be done with the same ship used to fly there.