Practical propulsion methods for manned interplanetary travel

[Nuke]

Depends on the state of 3D printing in 2038 and if it easier to use the resources on site rather than ship them from earth. A lot could change in 24 years, look at computers! Or nothing could change..... Though with the leaps and bounds the technology in 3D printing has made in a few short years I can see progression carrying on.

Well as I already stated your free from political and environmental problems on mars or the moon so you have a lot of leeway on propulsion methods and energy production.

we are already printing in concrete at a very large scale. and there are shipyard scale cnc machines for building carbon fiber composite boat hulls. so i can imagine our first extra planetary bases might be 3d printed by robots long before humans get there. lunacrete and bricks (made using lunar basalt sintering robots) would be fairly good materials. im actually looking forward to seeing swarm robotic based 3d printing systems.

[crazyewok]

Well that only leaves:

1) chems

2) not bothering

3) useing orbital, lunar or mar contruction to get round political and enviromental restrictions.

4) hopeing a novel propulsion method appears.

[mdatspace]

Well that only leaves:

1) chems

2) not bothering

3) useing orbital, lunar or mar contruction to get round political and enviromental restrictions.

4) hopeing a novel propulsion method appears.

3 will not work. The colony will still have the regulation you are trying to avoid. The government of said country will enforce that regulation.

You can launch the nuclear engine into space and use it. NTR is acceptable if you do so. I am open to nuclear propulsion, but it has to abide by laws and regulations as I said(Nuclear test ban etc). NERVA is a good suggestion.

[mdatspace]

I think this thread has gone off topic. You are stuck with the restrictions on nuclear propulsion, Crazyewok. Look at my first post on this thread.

Edited January 29, 2014 by mdatspace

[Nuke]

we could probibly launch a dry reactor and fuel it in space. spread out the launch of fuel rods across multiple missions. these would accompany missions to launch the hydrogen propellant and other consumables. much of the mother ship would be launched on one rocket, and you might launch the lander and crew on another.

1 put nerva mothership in orbit unfueled

2 several robotic fueling/stocking missions (reactor fuel rods are placed in protective casks for launch, and could be ejected and parachuted down if a problem is detected)

3 launch landing package and crew (they can ride up in the lander)

[shynung]

9 months is not that long for the trip. Look at folks on the ISS. A number of astronauts and cosmonauts have done that. I don't think you would need a skyscraper sized ship to do it (you don't need that much tonnage of supplies).

Something to consider, supply wise, is the fact they need to stay on Mars for about 500 days until the next Earth return window (assuming a return trip). That means supplies for the trip there, trip back, and 500 day mission.

Consider this: The signal from the rover took about 14 minutes to reach the control stations on Earth. Any astronaut going that distance would be reduced, in terms of communications, to sending emails. This communication lag could put mental pressure on the astronauts, especially those used to ISS missions where direct video-and-voice comms are available.

Also note that abort modes after going to interplanetary space is going to be scarce. Should the mission be cancelled for any reason, the poor souls onboard have little chance of survival. Going on this sort of mission is bordering on suicide; should any error occur, that would be it.

I agree that the ship may not need to be skycraper-sized, but I'd guess it would still be big. The ISS have regular supply launches to support them, which is why it is habitable for quite some time. A Mars-bound ship have no access to this sort of resupply, and have to carry everything from LEO. Add scientific equipments, labs, landers, and all sorts of thing needed for a Mars manned mission, and that would result in a very heavy ship. This would necessitate plenty of fuel, both to get itself there and back, and to fuel any landers they carry. Add the fact that it has to carry everything on its own, and that results in a large ship.

[Soda Popinski]

Consider this: The signal from the rover took about 14 minutes to reach the control stations on Earth. Any astronaut going that distance would be reduced, in terms of communications, to sending emails. This communication lag could put mental pressure on the astronauts, especially those used to ISS missions where direct video-and-voice comms are available.

Also note that abort modes after going to interplanetary space is going to be scarce. Should the mission be cancelled for any reason, the poor souls onboard have little chance of survival. Going on this sort of mission is bordering on suicide; should any error occur, that would be it.

I agree that the ship may not need to be skycraper-sized, but I'd guess it would still be big. The ISS have regular supply launches to support them, which is why it is habitable for quite some time. A Mars-bound ship have no access to this sort of resupply, and have to carry everything from LEO. Add scientific equipments, labs, landers, and all sorts of thing needed for a Mars manned mission, and that would result in a very heavy ship. This would necessitate plenty of fuel, both to get itself there and back, and to fuel any landers they carry. Add the fact that it has to carry everything on its own, and that results in a large ship.

It is actually quite possible for a group of humans to willingly cut themselves off from society for months or years at a time without going completely crazy. Look at any historic exploration mission, such as treks to the North or South pole, the voyage of Columbus or Magellan. That is far, far worse than having to wait 30 minutes round trip for a reply.

As to the lack of a rescue, that would be the truth with any mission to Mars, no matter what the propulsion system is. They can't really do a free return trajectory, like with the Moon. I can't see the mission being cancelled after it was launched being particularly realistic.

As to the size, NASA's Mars Reference Architecture 5 has a crew vehicle which is 97 meters long. It's mostly fuel tanks. While large, I wouldn't call it skyscraper sized. The design also saves on mass by harvesting oxidizer for the ascent stage of the lander from the surface of Mars, along with drinking water and breathing oxygen.

[sgt_flyer]

Well, if they plan to harvest drinkable water and oxydizer from mars, they should directly switch to methalox engines and make the fuel on mars too, for even greater savings ( plus methane would be a lot easier on longterm storage than keeping Liquid hydrogen for 500 days. (They can process methane from water + co2 - additional benefit is to produce directly oxygen as a byproduct

[magnemoe]

When did I say you were not allowed to use anything other then chemical engines? Quite a misrepresentation.

Building a shipyard on the Moon or Mars just because you can supposedly bypass restrictions on propulsion systems does not justify the costs compared to just sticking with chemical engines and using fuel depots. This is what I think.

This thread has gone off topic.

The reason why nobody uses nerva type engines is that they are kind of overkill for small probes who is all we do.

Yes it will also require more testing before use, including an dummy long term test in space. Probably using hydrogen for start and some other gas for braking and return as hydrogen is hard to store for months. This adds to the cost so you will not use nerva on an probe where it would be marginally better.

Where is an law against having nuclear weapons in space. No issues with reactors, an nerva is an nuclear reactor who eject the cooling medium, some plans with vasmir uses an nuclear engine for power, this has the benefit that vasmir has better isp than nerva.

It was also no complains about the current mars rover with its rtg, no its not an real reactor but I don't think many know the difference.

[Ralathon]

Lets see, with those restrictions I'd probably go the Mars 1 route and combine the "Mars Colony" and "Mars landing" objectives. Maybe I'll give the poor guys a return vehicle later on, but they're stuck there for a few decades.

To maximize payload I'd still go with a nuclear engine. So my launch profile would look like this:

Step 1: Launch NERVA engines with fuel tanks, use this as second stage to save on costs. So you end up with a big NERVA engine with half empty fuel tanks in orbit. If you want to be really fancy you can use a section of the fuel tank as a wet workshop so you can give the astronauts a nice spacious home during the interplanetary trip after the earth ejection burn.

Step 2: Launch refueling missions to top off the NERVA stage. Use these to also bring up inflatable hab modules. The Hab modules need removable heat shields so you can use them both in space and on the martian surface.

Step 3: Bring up the science equipment and the astronauts. This should speak for itself. The astronauts will spend some time getting the science equipment sorted, reinforcing structural connections etc. Might be useful to assemble it near the ISS so astronauts can easily ferry things around between the 2 and reuse experiments designed for the ISS.

Step 4: The actual trip. Preform the ejection burn and go for Mars. Once the ejection burn is done you can inflate all your hab modules and clean your wet workshop. Then you'll spend the next 6 months twiddling your thumbs as you wait for Mars. I'm thinking a crew of 6 will do, trained in various sciences obviously. Keep in contact with them throughout the trip, people appreciate emails from loved ones etc.

Step 5: Arrival at Mars. Use the last dregs of fuel to slow yourself down to enter a highly elliptic orbit and use the next few months to slowly aerobrake into a circular orbit. Maybe send out a few trips to Phobos and Deimos since you're there anyway. Asteroid landings are cheap on fuel.

Step 6: Landing. The first things to go down should be a power supply and some life support. After that you can send the crew and habitation modules in any order. If your drive stage was a wet workshop leave it in orbit for future missions, else just dump it into the atmosphere.

From here on out you keep it supplied with food and water via relatively cheap care packages. They should be designed so you can actually live in them once they're empty, to slowly build out the base. As older modules start to wear down you want to send them some production facilities, a big 3D printer and some chemical setup that provides material for the printer would be ideal. If you ever want to get them back you'll probably have to send another big mission though.

[shynung]

It is actually quite possible for a group of humans to willingly cut themselves off from society for months or years at a time without going completely crazy. Look at any historic exploration mission, such as treks to the North or South pole, the voyage of Columbus or Magellan. That is far, far worse than having to wait 30 minutes round trip for a reply.

As to the lack of a rescue, that would be the truth with any mission to Mars, no matter what the propulsion system is. They can't really do a free return trajectory, like with the Moon. I can't see the mission being cancelled after it was launched being particularly realistic.

As to the size, NASA's Mars Reference Architecture 5 has a crew vehicle which is 97 meters long. It's mostly fuel tanks. While large, I wouldn't call it skyscraper sized. The design also saves on mass by harvesting oxidizer for the ascent stage of the lander from the surface of Mars, along with drinking water and breathing oxygen.

I suppose I did not take the ship's resource extraction capability into account. Yes, that would significantly lower the launch mass of the ship, and its size along with it.

The only other problem I could think of is dealing with zero-g effects on the astronauts, but it is solvable by deploying centrifuges, which are possible using today's technology.

So, to answer the OP's question, a slighty scaled-up Apollo-style mission to Mars by 2025 using technology available today is certainly feasible, although I doubt NASA or anyone would actually do it that way.

EDIT: I agree with the post above about combining landing and colony mission in one shot. This would cut fuel use for the trip at least by half, as there wouldn't be any need for a return trip.

Edited January 29, 2014 by shynung

[crazyewok]

.

NERVA is a good suggestion.

I thought that was what we were talking about! I got the impression all nuclear was banned. my mistake

Yeah that would work. NERVA could get you to the belt.

[Soda Popinski]

I suppose I did not take the ship's resource extraction capability into account. Yes, that would significantly lower the launch mass of the ship, and its size along with it.

The only other problem I could think of is dealing with zero-g effects on the astronauts, but it is solvable by deploying centrifuges, which are possible using today's technology.

So, to answer the OP's question, a slighty scaled-up Apollo-style mission to Mars by 2025 using technology available today is certainly feasible, although I doubt NASA or anyone would actually do it that way.

EDIT: I agree with the post above about combining landing and colony mission in one shot. This would cut fuel use for the trip at least by half, as there wouldn't be any need for a return trip.

While it's nice to be agreed with, the fuel wouldn't be cut in half due to extraction from the surface. That's ONLY the oxidizer for the ascent module. The fuel is liquid methane, and being brought from Earth (as any good KSPer knows, oxidizer is heavier than "liquid fuel" and I think you need 2 parts LOX to 1 part methane). The fuel and oxidizer for the return trip stays in orbit and came from Earth (oxidizer if we're talking the chemical method, no oxidizer if NTR).

So NASA has a plan to get to Mars using conventional chemical propulsion. It still requires a nuclear reactor on the surface to extract oxygen from the atmosphere, so will that fly? (get it?)

[shynung]

While it's nice to be agreed with, the fuel wouldn't be cut in half due to extraction from the surface. That's ONLY the oxidizer for the ascent module. The fuel is liquid methane, and being brought from Earth (as any good KSPer knows, oxidizer is heavier than "liquid fuel" and I think you need 2 parts LOX to 1 part methane). The fuel and oxidizer for the return trip stays in orbit and came from Earth (oxidizer if we're talking the chemical method, no oxidizer if NTR).

So NASA has a plan to get to Mars using conventional chemical propulsion. It still requires a nuclear reactor on the surface to extract oxygen from the atmosphere, so will that fly? (get it?)

I was thinking that the fuel requirements would be cut by half due to the fact that the spacecraft, including the Mars-injection engines, would never come back to Earth. If nuclear propulsion systems are to be used, it's more likely that the nuclear reactor would be carried along to the surface, for use as power plant. Whatever remains of the Mars-injection spacecraft would be left in orbit, or crash-landed somewhere else.

That is, of course, if the mission is a one-way trip. Which means, anyone going for Mars would start a colony, and stay there for the rest of their lives, away from the rest of humanity, except for a 30-minute-lagged communications system.

BTW, when I said 'the post above', I meant Ralathon's. Sorry for that.

[Soda Popinski]

I was thinking that the fuel requirements would be cut by half due to the fact that the spacecraft, including the Mars-injection engines, would never come back to Earth. If nuclear propulsion systems are to be used, it's more likely that the nuclear reactor would be carried along to the surface, for use as power plant. Whatever remains of the Mars-injection spacecraft would be left in orbit, or crash-landed somewhere else.

That is, of course, if the mission is a one-way trip. Which means, anyone going for Mars would start a colony, and stay there for the rest of their lives, away from the rest of humanity, except for a 30-minute-lagged communications system.

BTW, when I said 'the post above', I meant Ralathon's. Sorry for that.

My mistake.

The NASA plan, using chemical means, also plans to save on propellant by using aerocapture. Works for Mars, but not so good for any non-atmospheric bodies out there. I doubt chemical means can be used for getting past Mars. The OP said NERVA is fine, so within those constrains, Jupiter in about 2 to 2.5 years is said to be reachable.

[Lordherrmann]

2 - 2.5 years to Jupiter is too long IMO. Mars is pretty much reachable with current chemical propulsion technology as was already stated multiple times in this thread. I'd go for NTR or chemical to reach Mars by 2025. For the outer solar system I'd use fusion propulsion. I recently did some research about it for a paper I wrote and this stuff is mighty. It may not be available today, but the guys and gals at ITER are working hard to make it happen but 2023.

During my research I found a reference mission proposed in 2005 by the Glenn Research Center. With the proposed mission architecture it would be possible to send 127 metric tons of payload to Jupiter in 118 days, using about 800 metric tons of LH2 as a propellant and about 11 tons of a mixture of helium 3 and deuterium.

[Soda Popinski]

2 - 2.5 years to Jupiter is too long IMO. Mars is pretty much reachable with current chemical propulsion technology as was already stated multiple times in this thread. I'd go for NTR or chemical to reach Mars by 2025. For the outer solar system I'd use fusion propulsion. I recently did some research about it for a paper I wrote and this stuff is mighty. It may not be available today, but the guys and gals at ITER are working hard to make it happen but 2023.

During my research I found a reference mission proposed in 2005 by the Glenn Research Center. With the proposed mission architecture it would be possible to send 127 metric tons of payload to Jupiter in 118 days, using about 800 metric tons of LH2 as a propellant and about 11 tons of a mixture of helium 3 and deuterium.

Yep, that reference mission was one of the 2 inspirations for my own Discovery 2 to Jool Mission. Guess which the other inspiration was. Anyway, that spherical torus fusion drive can hit an Isp of 20,000 to 30,000 sec with high thrust. That would certainly do it.

[Simon Ross]

OK, I really hate to rain on the parade but ...

Mars isn't 'reachable' with the technology we have today

If you want to do a manned mission with existing chemical boosters your looking at a minimum of a 3 year round trip

The ISS is just above us in LEO, after $100 billion it can barely sustain itself for 3 MONTHS let alone 3 years

We don't have the life support capability to do a 3 year mission

We don't have the booster technology to shorten the mission

In short, we cannot do the mission

[Soda Popinski]

OK, I really hate to rain on the parade but ...

Mars isn't 'reachable' with the technology we have today

If you want to do a manned mission with existing chemical boosters your looking at a minimum of a 3 year round trip

The ISS is just above us in LEO, after $100 billion it can barely sustain itself for 3 MONTHS let alone 3 years

We don't have the life support capability to do a 3 year mission

We don't have the booster technology to shorten the mission

In short, we cannot do the mission

Why don't we have the booster technology? Anybody who plays KSP knows you can increase delta-V, and hence shorten the trip by using MOAR BOOSTERS.

That depends on what we define as "today's technology."

If we mean chemical rockets, then yes we can. As pointed out in this thread, NASA's current Mars mission plans include using chemical rockets to get to Mars in 7 months, 18 months there, and 7 months back. Water and oxygen will be produced from the Martian atmosphere while they're on the surface, so that reduces the life support supplies.

If you allow the 1970s NERVA technology to count as today's technology, then the same trip can be done with fewer launches (7 versus 12).

If you mean, "today" as in Wednesday, Jan 29th, then no. We don't have the Ares I / Ares V systems ready to go.

Again, here's a link to the NASA Mars Research Architecture 5. No break through technology required. Just a lot of will and funding.

Edited January 30, 2014 by Soda Popinski

[Nuke]

2 - 2.5 years to Jupiter is too long IMO. Mars is pretty much reachable with current chemical propulsion technology as was already stated multiple times in this thread. I'd go for NTR or chemical to reach Mars by 2025. For the outer solar system I'd use fusion propulsion. I recently did some research about it for a paper I wrote and this stuff is mighty. It may not be available today, but the guys and gals at ITER are working hard to make it happen but 2023.

During my research I found a reference mission proposed in 2005 by the Glenn Research Center. With the proposed mission architecture it would be possible to send 127 metric tons of payload to Jupiter in 118 days, using about 800 metric tons of LH2 as a propellant and about 11 tons of a mixture of helium 3 and deuterium.

iter/demo wont give us anything we can use in space. tokamaks have a minimum size that is a major physical limit to how small you can make a reactor. it might generate data that is useful in other lines of reactor research, and may produce breakeven terrestrial power reactors in time. its the compact reactor designs you really want to place your bets on for use in space. dense plasma focus fusion would be a very small sized reactor. a polywell (its supporters are a little less radical than the dpf croud, which is a good sign) would be small enough to put in a space craft (3 meters for the polywell), its also going to be capable of direct conversion under the p-b11 reaction, thus removing heavy thermodynamic engine: pumps, coolant loops, radiators, turbines, generators, etc, from the reactor (you might still have one to eliminate and utilize reactor waste heat, but not as big).

[Simon Ross]

@Soda

Sorry, but Ares I / Ares V doesn't get close to mounting a manned Mars mission. Basically your back with using Apollo level HLV technology with all the constraints of that technology. Sure, studies were done in the 60's to mount a Mars mission using Apollo hardware, but that's as far as they ever got, just studies. Unfortunately you simply face the same issues using SLS as the basis for a Mars mission, in almost 50 years nothing has really changed.

Until we grow up and use nuclear we are stuck in LEO

Edited January 30, 2014 by Simon Ross

[Soda Popinski]

@Soda

Sorry, but Ares I / Ares V doesn't get close to mounting a manned Mars mission. Basically your back with using Apollo level HLV technology with all the constraints of that technology. Sure, studies were done in the 60's to mount a Mars mission using Apollo hardware, but that's as far as they ever got, just studies. Unfortunately you simply face the same issues using SLS as the basis for a Mars mission, in almost 50 years nothing has really changed since.

Until we grow up and use nuclear we are stuck in LEO

Please read the 2009 NASA Mars Research Architecture 5, and tell me why the chemical rocket contingency wouldn't work.

Read section 4.4, "Chemical/Aerocapture Option." It outlines the use of 15 1960s era RL10 rocket engines on 3 Trans Mars Injection modules to attain the require 4 km/s delta-V from Earth orbit.

What's wrong with the Ares I / V system? The reference states NTRs are the best option (which I'm sure you'll agree), but to get them to orbit, the plan is to use the Ares I / Ares V system, unless you think it's a good idea to launch from Florida using nuclear rockets. The same Ares I / Ares V system would be used to assemble a chemical rocket based mission, it'll just take twice as many launches as an NTR based one.

Edited January 30, 2014 by Soda Popinski

[Simon Ross]

@Soda

It wont work for exactly the same reason the studies in the 60's fell down. The delta v isn't the issue, building a life support system that can operate independent of Earth support for 3 years is the issue.

If you want to do a manned Mars Mission, you need a HUGE amount of redundancy built into the system and every gram you have to add to the system costs money to get off the ground.

With current chemical booster tech, forget it, it isn't going to happen

I was born in 1960, watched the first men land on the moon. Two decades ago I kinda realised that I was never going to see a person land on Mars in my lifetime, what scares me is that I don't think any of us posting on this thread are going to see it :-(

[peadar1987]

With today's technology, we could absolutely mount a manned Mars mission.

With today's currently-existing hardware, we could not.

Big difference between the two, but even if scientific knowledge completely stagnated tomorrow, we would still have the knowhow to design and build a craft with enough delta-v to get to Mars and back using chemical rockets.

[Soda Popinski]

@Soda

It wont work for exactly the same reason the studies in the 60's fell down. The delta v isn't the issue, building a life support system that can operate independent of Earth support for 3 years is the issue.

...

With current chemical booster tech, forget it, it isn't going to happen

The NASA architecture gives the same mission time whether they use NTRs or chemical rockets - 2.5 years (539 days on Mars, rest travel time). Why does having NTRs over chemical rockets change the life support requirements if the mission time is the same? If you're curious about how they plan to do life support (at least oxygen & water), read section 5.3.

I was born in 1960, watched the first men land on the moon. Two decades ago I kinda realised that I was never going to see a person land on Mars in my lifetime, what scares me is that I don't think any of us posting on this thread are going to see it :-(

Probably right. But we're talking possibilities here, not political will.