Practical propulsion methods for manned interplanetary travel

[Kryten]

If we could build a closed-loop system using current technology, we'd be using at least some of that technology on the ISS; it's not as if resupply launches are cheap.

[Soda Popinski]

If we could build a closed-loop system using current technology, we'd be using at least some of that technology on the ISS; it's not as if resupply launches are cheap.

They are. They recycle their waste water for drinking (see video). Resupply launches include scientific experiments and new crew members. The ISS is theoretically up there to do science, without sending up new experiments, it's sort of a waste. It's much more economical to send up consumables while sending up the payload required for the mission.

The alternative would be to launch a decade's worth of food, oxygen, replacement water, etc and have that docked to the ISS for a decade, increasing it's mass, requiring more propellant for station keeping, and eating up a docking node.

You don't need to do that for the ISS. The Mars plan on the other hand has about 10t of food canisters on the manifest (table 4-1).

[Simon Ross]

False premise. The ISS is not evidence we cannot build a closed system for 3 years. It is not an attempt to do so. The ISS is designed to have new experiments go up every few months. So why bother making it self sufficient for years?

Just because my car doesn't fly, doesn't mean flight is impossible.

In other words, we can build a self sufficient system with current technology, we just haven't done it yet.

Soda

I'm actually an engineer, if you try to build 'proof of concept' models you do it where it is safe, you do it where humans can be kept from harm or in the worst possible case, they can effect an escape and rescue.

The ISS should be the place we have flight tested these concepts

Cold hard facts, we haven't

No proof of concept for a 3 year unsupported life support system, no proof of concept for an artificial gravity system.

Or do you think we should really be testing these things on an actual 3 year mission 35 million miles away with real life people ?

Edited February 5, 2014 by Simon Ross

[Kryten]

They are.

That's my point, and the big problem. Yes, they've got a state-of-the-art water recycling system on the ISS, but it's one that fills large portions of two modules and requires topping up to the tune of three tons a year. It's barely closer to closed-cycle than the systems on Mir.

[Soda Popinski]

No proof of concept for a 3 year unsupported life support system, no proof of concept for an artificial gravity system.

Or do you think we should really be testing these things on an actual 3 year mission 35 million mile away with real life people ?

Of course not.

I think our argument is going in circles because you are arguing we don't have the hardware to do it, and I'm arguing we have the technology to do it. I feel technology and hardware are two different things. I agree we don't have the hardware to do it right now. The hardware would of course have to be developed and proved before such a mission would be under taken.

[Roastduck]

I think when it comes to a closed-loop life support system, technology and hardware go hand in hand. If we had the technology, we would have created the hardware by now.

[Simon Ross]

Of course not.

I think our argument is going in circles because you are arguing we don't have the hardware to do it, and I'm arguing we have the technology to do it. I feel technology and hardware are two different things. I agree we don't have the hardware to do it right now. The hardware would of course have to be developed and proved before such a mission would be under taken.

I go back to one of the OP criteria

'Technology:Must be viable today'

Not proven, therefore not viable

We cannot do it

Sorry, I actually don't like that answer any more then you do :-(

[Soda Popinski]

I go back to one of the OP criteria

'Technology:Must be viable today'

Not proven, therefore not viable

We cannot do it

Sorry, I actually don't like that answer any more then you do :-(

By that criteria we don't have the technology/hardware viable today to go to the Moon. We don't have a Saturn V class rocket, nor a lander built, nor a CM.

I'll actually go back to the OP criteria (and title), asking for "propulsion methods."

Life support isn't propulsion (unless beans are involved). You originally argued we needed nuclear thermal rockets (NTR) to have a short enough mission to be viable due to constraints of life support. I showed the NASA plans using both NTR and chemical rockets can achieve the same travel time to Mars. Either one will require life support for almost 2 years while the astronauts do their science and wait for a launch window. So in that case, NTRs won't help.

So if you think NTRs are the limiting factor for a Mars mission, and chemical rockets can perform the exact same mission (with more launches and costing more), then we are not limited by today's propulsive technologies. You can argue we are limited by today's life support technologies, but I think that's semantics between hardware and technology. Where does one draw the line?

Edited February 5, 2014 by Soda Popinski

[Kryten]

By that criteria we don't have the technology/hardware viable today to go to the Moon. We don't have a Saturn V class rocket, nor a lander built, nor a CM.

We have all of the technology to do that. We have engines of the requisite performances, heat-shielding that works well enough, et.c.; what we don't have is the money or political will. By contrast, do need life support equipment far more efficient and lightweight than anything we can produce today for a Mars mission.

[Soda Popinski]

We have all of the technology to do that. We have engines of the requisite performances, heat-shielding that works well enough, et.c.; what we don't have is the money or political will. By contrast, do need life support equipment far more efficient and lightweight than anything we can produce today for a Mars mission.

My point was Simon's point is hardware = technology.

Since we don't have a Saturn V built and ready to go, and even if we started manufacturing them again, they'd have to be requalified, and made with new materials (can't use asbestos in the thermal blankets on that F-1 engine again). Since our imaginary new Saturn V hasn't been built, nor tested, the hardware doesn't exist, and therefore, by Simon Ross' definition, is not a viable technology available today.

You don't need life support to be more efficient or lightweight. You can just put it on a bigger rocket. It's not ideal, but it's not beyond our technology to put 10 tons of supplies into LEO as per the Mars Reference Architecture.

Edited February 5, 2014 by Soda Popinski

[Soda Popinski]

That's my point, and the big problem. Yes, they've got a state-of-the-art water recycling system on the ISS, but it's one that fills large portions of two modules and requires topping up to the tune of three tons a year. It's barely closer to closed-cycle than the systems on Mir.

Sorry, I missed this one.

Are we incapable of sending 10 tons of water into LEO?

[Rakaydos]

Yes, you would test stuff like artificial gravity and 6 months witout resupply closer to home. When we get the political will to start the mars mission, we'll put an artificial gravity wheel in orbit to test it. Meanwhile an antarctic base will test the life support system. (because when testing your air system, even being 40 minutes from help can be lethal)

[Kryten]

Since we don't have a Saturn V built and ready to go, and even if we started manufacturing them again, they'd have to be requalified, and made with new materials (can't use asbestos in the thermal blankets on that F-1 engine again). Since our imaginary new Saturn V hasn't been built, nor tested, the hardware doesn't exist, and therefore, by Simon Ross' definition, is not a viable technology available today.

But we do have RD-170s that are close enough in power and ISP to be used for a roughly equivalent rocket. By contrast nobody has created a life support system with the efficiency, reliability, and mass you'd need for this kind of mission, ever.

Sorry, I missed this one.Are we incapable of sending 10 tons of water into LEO?

There's a lot more to life support than water. Add in the weight of the recycling system itself, the weight of the oxygen production system, the weight of the thermal management system, spare parts for all three, the airlock and suits you'd need to maintain some of these systems, a habitat big enough for all this stuff with enhanced radiation shielding, s storm shelter for CMEs, and a big enough propulsion system to send all of these things out of earth orbit, and the answer very definitely becomes yes.

[Simon Ross]

My point was Simon's point is hardware = technology.

Since we don't have a Saturn V built and ready to go, and even if we started manufacturing them again, they'd have to be requalified, and made with new materials (can't use asbestos in the thermal blankets on that F-1 engine again). Since our imaginary new Saturn V hasn't been built, nor tested, the hardware doesn't exist, and therefore, by Simon Ross' definition, is not a viable technology available today.

You don't need life support to be more efficient or lightweight. You can just put it on a bigger rocket. It's not ideal, but it's not beyond our technology to put 10 tons of supplies into LEO as per the Mars Reference Architecture.

I'm sorry, but what is this bigger rocket ?

The first couple of iterations of SLS don't even get the payload of Saturn V into LEO yet you think this is going to be the system to get us to Mars ?

Sorry it isn't going to happen

Please read up on your history, we had this payload capability 40 years ago, couldn't do it then with any reasonable chance of success

In all that time, not a whole lot has changed other then NASA has changed from a civilian space programme with clear and funded goals to simply a means to keep a lot of aerospace engineers employed on make work

[metaphor]

There's a lot more to life support than water. Add in the weight of the recycling system itself, the weight of the oxygen production system, the weight of the thermal management system, spare parts for all three, the airlock and suits you'd need to maintain some of these systems, a habitat big enough for all this stuff with enhanced radiation shielding, s storm shelter for CMEs, and a big enough propulsion system to send all of these things out of earth orbit, and the answer very definitely becomes yes.

Isn't that just a lot of mass? We have the technology to put up a lot of mass into orbit. We just aren't willing to spend the money to do it.

We already have all the technology to send people to Mars (or anywhere else in the solar system), even if it's just the "brute force" method. But we are working on better technology to make it more efficient and cheaper.

[Soda Popinski]

I'm sorry, but what is this bigger rocket ?

Exactly my point about your point. Since we don't even have the hardware available today to get to the Moon, then we don't have the technology to go to the Moon much less Mars. If this is your definition of "technology" then I agree with you.

My original point was that a chemical fuel rocket is a propulsion system capable of getting a crew to Mars, and that neither NTR (even though I would consider that today's technology, as it was developed and ground tested in the 1970s), gas core fission, spherical toroidal fusion, nor any other exotic form of propulsion would be needed to complete this goal. The stay time on Mars would still be about 2 years no matter the propulsion technology.

The first couple of iterations of SLS don't even get the payload of Saturn V into LEO yet you think this is going to be the system to get us to Mars ?

Sorry it isn't going to happen

Of course it won't happen. I never argued it would. It's a political non-starter. The point of the argument is it is possible with chemical rocket technology. Do you disagree with this premise? If so, how would the NTR technology you said would be needed make it possible where a chemical rocket doesn't work? As I mentioned, either way, you need life support for 2 years.

*I'm wrong on this, the Architecture gives a long stay (500 day stay, 30 month total round trip) and a short stay (30-90 days stay 22 month total round trip).

[3_bit]

I think Nuclear fusion may be our solution. I've read some pretty interesting and ambitious papers, but if we were to invest ~$30 billion and give it a decade or two, we could have Deuterium-Deuterium or deuterium-Helium3 (that stuff you hear of in sci-fi films of being scraped from the Lunar surface) fusion be a viable energy source, with generators actually reaching breakeven (outputting more than they take in). A hypothetical spacecraft could use a later model of this reactor, with 0 radioactive output, and, assuming we develop the technology, send a kilogram into LEO for $27 a pound. Of course, I don't know how ambitious that number is, but nuclear fusion does sound quite exciting.

[Rakaydos]

Fusion power has been "A decade away" for the last half century. :/

[Nuke]

Fusion power has been "A decade away" for the last half century. :/

thats because we keep funding tokamaks.

expensive beasts, slow to construct, they are. [/yoda]

bussard said it better

Edited February 6, 2014 by Nuke

[KASASpace]

Guys, the Space Act says you can't put anything nuclear in space. Not a NERVA, not an Orion, no nuclear reactions. Nadda, zip. You would have to wait till AT LEAST 2038 till you can get enough people to accept that it's okay to launch NERVA, but, wait, deadline! So, I would use LH2/Fluorine, but only in space. Of course it's expensive, but I wouldn't need a HUGE base/colony. And I would use Falcon Heavy Launch Vehicle, as well. Coupled with Angara.

[Kryten]

Guys, the Space Act says you can't put anything nuclear in space. Not a NERVA, not an Orion, no nuclear reactions. Nadda, zip.

Prove it. Find one actual piece of ratified legislation that bans anything other than nuclear weapons in space.

[KASASpace]

Prove it. Find one actual piece of ratified legislation that bans anything other than nuclear weapons in space.

http://history.nasa.gov/1967treaty.html

Article IV

It says weapons, but anything that undergoes a nuclear reaction can be used as a weapon.

And Orion uses actual Nukes, and NERVA could "accidentally" go critical. And let-alone the political reasons, if it goes critical then the USA, if the USA launched it, would be responsible. I would do it if other countries didn't mention this treaty and say, "It can be used as a weapon!"

Edited February 6, 2014 by KASASpace

[Kryten]

Article IV

It says weapons, but anything that undergoes a nuclear reaction can be used as a weapon.

That's complete nonsense. 'Nuclear weapons' has a very specific definition, and it doesn't include reactors. The USSR launched no less than 35 nuclear reactors into orbit after signing that treaty, and the UN didn't say a word.

EDIT:

NERVA could "accidentally" go critical

I'd go further than that; I'd say a NERVA would definitely and deliberately go critical. Why? Because that's what a nuclear reactor is supposed to do.

Edited February 6, 2014 by Kryten

[KASASpace]

That's complete nonsense. 'Nuclear weapons' has a very specific definition, and it doesn't include reactors. The USSR launched no less than 35 nuclear reactors into orbit after signing that treaty, and the UN didn't say a word.

Launch Dates? Before 1967, when the agreement was signed, the USA detonated a nuke in space.

And it doesn't matter the "definition" of Nuclear Weapons. Reactors or not, it handles nuclear material and has the possibilty to "go critical" and what if the Nerva stayed on after aburn, no coolant, and BOOM. And "weapon" could mean anything, "nuclear" denotes to it involving nuclear forces. So, if I put a "reactor" into space and it exploded, then I would get blamed, and it would violate the Space Act. Other countries might assume it was intentional, and that it was a weapon, of the nuclear type. Thus violating the Space Act and getting me into serious trouble.

And if you want to go into solid nuclear terms, than replace "critical" in this post with "super-critical"

Edited February 6, 2014 by KASASpace

[Kryten]

Launch Dates? Before 1967, when the agreement was signed, the USA detonated a nuke in space.

Interestingly enough, that's not banned by this treaty, as a quick glance at it would tell you. It only bans the placing of nuclear weapons in orbit. As for the dates, 1967-1988.

And it doesn't matter the "definition" of Nuclear Weapons. Reactors or not, it handles nuclear material and has the possibilty to "go critical

I would hope it would, given being able to 'go critical' is literally the definition of what a nuclear reactor is. With regards to the definition, feel free to petition the UN if you think they should be using yours.

what if the Nerva stayed on after aburn, no coolant, and BOOM.

There's nothing in the design even capable of 'going boom'; at most, it'd melt. Do you get all of your physics from bad films? Having 'nuclear' in the name≠will go off like little boy.

And "weapon" could mean anything, "nuclear" denotes to it involving nuclear forces.

By that definition, you're a nuclear weapon; you're fundamentally held together by nuclear forces, and you're capable of inflicting suffering on people. I really shouldn't have to say this isn't actually how international treaties work.