Practical propulsion methods for manned interplanetary travel

[Simon Ross]

@Soda

NTR doesn't change the mission time

As I have already stated, it's not about delta v. we can do that with chemicals, it's about the amount of redundancy you need to include in the mission profile to give the passengers a realistic chance of surviving the mission.

Without NTR, you are simply never going to see this mission happen

[Soda Popinski]

How do Nuclear Thermal Rockets increase redundancy?

By the way, the NASA architecture sends 2 redundant In-Situ Resource Utilization (ISRU) plants to the Mars surface ahead of the crew launch. Crew launch won't even happen until confirmation of oxygen (breathing and oxidizer), water, and buffer gasses is confirmed on the surface from the ISRUs. There's your redundancy.

[Simon Ross]

How do Nuclear Thermal Rockets increase redundancy?

By the way, the NASA architecture sends 2 redundant In-Situ Resource Utilization (ISRU) plants to the Mars surface ahead of the crew launch. Crew launch won't even happen until confirmation of oxygen (breathing and oxidizer), water, and buffer gasses is confirmed on the surface from the ISRUs. There's your redundancy.

Well, it's very simple, if all you have is chemical boosters to get mass into orbit how many launches do you need to put a Mars capable system up there ?

If you use a NTR upper stage, you reduce the launches by half

Kinda simple economics

We need NTR, simply because bugger all is going to happen otherwise

[Soda Popinski]

Well, it's very simple, if all you have is chemical boosters to get mass into orbit how many launches do you need to put a Mars capable system up there ?

If you use a NTR upper stage, you reduce the launches by half

Kinda simple economics

We need NTR, simply because bugger all is going to happen otherwise

Ah, so its merely an economic argument. 12 launches with chemical using Ares I/V versus 7 launches with NTR using Ares I/V, according to the NASA architecture.

Your first point was that chemical rockets would take 3 years minimum, and we don't have the life support capabilities to handle 3 years. You said we need better booster technology to shorten the mission. I countered either NTR or chemical rockets would take 2.5 years, and that the life support requirements would be identical with either NTR or chemical (based on the NASA architecture).

Then you said we need NTRs for life support redundancy. I countered the NASA plan has redundancy built with chemical rockets.

Now you're saying it's not feasible because it'll take too many launches if we do a chemical rocket based approach, compared to NTR.

So your argument against chemical rockets has been 1) Takes too long, 2) not redundant, 3) too expensive, due to too many launches.

We're talking 12 launches. The ISS has had 32 launches for assembly.

I'll agree we don't have the political will to get the funding for something like this, but the thread is asking about the possibility with current technology.

[Simon Ross]

Ah, so its merely an economic argument. 12 launches with chemical using Ares I/V versus 7 launches with NTR using Ares I/V, according to the NASA architecture.

Your first point was that chemical rockets would take 3 years minimum, and we don't have the life support capabilities to handle 3 years. You said we need better booster technology to shorten the mission. I countered either NTR or chemical rockets would take 2.5 years, and that the life support requirements would be identical with either NTR or chemical (based on the NASA architecture).

Then you said we need NTRs for life support redundancy. I countered the NASA plan has redundancy built with chemical rockets.

Now you're saying it's not feasible because it'll take too many launches if we do a chemical rocket based approach, compared to NTR.

So your argument against chemical rockets has been 1) Takes too long, 2) not redundant, 3) too expensive, due to too many launches.

We're talking 12 launches. The ISS has had 32 launches for assembly.

I'll agree we don't have the political will to get the funding for something like this, but the thread is asking about the possibility with current technology.

OK, so lets put this into language we can all understand

The ISS is a $100 billion 500 tonne structure that orbits above us in LEO. The ISS is self sufficient for approximately 3 months after that it is totally reliant on Earth based launches to keep it resupplied.

The ISS is the single biggest structure we have ever built in space yet it is only 250 miles away

It took over a decade to build using the technology we had

Are we capable of building a Mars capable system. No way ! Even with SLS

It's about keeping a crew alive for 3 years without earth support, it's something we cannot do with our existing technology.

TBH it's a pointless discussion. If chemical boosters are all we are ever going to have what's the point of any manned space programme? We might as well draw a map of the solar system and anything beyond a flag and footprints mission to Mars should just read ' Here be Dragons' it really is that simple.

Edited January 30, 2014 by Simon Ross

[Soda Popinski]

I get it. It's too expensive.

The proposed NASA chemical rocket based missions is 12 launches, totaling 796.2 (table 4-2). That will be assembled in LEO with 12 launches. Expensive, yes, but technologically possible (which is the point of the thread). Again, the ISS took 32 launches, also in LEO. So 12 launches seems technically possible to me.

So I'll concede it's expensive, and we'll never do it using our current technologies, due to budgetary and political reasons.

I still think it's technologically possible, as I disagree with the life support issue. The ISS needs resupply every 3 months because it's designed to be resupplied every 3 months.

3 years is a lot. But they don't need to bring all 3 years worth of supplies and life support. The In-Situ Resource Utilization plants will make the water and oxygen for their stay on the surface (and possibly the return trip). So they need to bring water, oxygen for the 400 days there and back, and food for the entire 900 days.

If you look a hundred years ago, when people first went to the North or South pole, they were outfitted with supplies for months they had to carry or pull with sleds. Hundreds of years before that, Columbus and Magellan set out to sea also with provisions for months for ships (for hundreds of crewmembers). They survived more than 3 months without re-provisioning, because they prepared expeditions that didn't require it.

The NASA study has 9.8 tons of food canisters for the 6 person crew. For 900 days, that's 1.8 kg of food per day per person (~4 pounds). Water is currently being recycled on the ISS right now. I suppose the question is shielding, but I'm pretty sure that just requires MOAR shielding. So we have food, water, oxygen for 3 years, climate control (PV powered), waste facilities, and shielding. What else is needed for life support?

[Simon Ross]

I get it. It's too expensive.

The proposed NASA chemical rocket based missions is 12 launches, totaling 796.2 (table 4-2). That will be assembled in LEO with 12 launches. Expensive, yes, but technologically possible (which is the point of the thread). Again, the ISS took 32 launches, also in LEO. So 12 launches seems technically possible to me.

So I'll concede it's expensive, and we'll never do it using our current technologies, due to budgetary and political reasons.

I still think it's technologically possible, as I disagree with the life support issue. The ISS needs resupply every 3 months because it's designed to be resupplied every 3 months.

3 years is a lot. But they don't need to bring all 3 years worth of supplies and life support. The In-Situ Resource Utilization plants will make the water and oxygen for their stay on the surface (and possibly the return trip). So they need to bring water, oxygen for the 400 days there and back, and food for the entire 900 days.

If you look a hundred years ago, when people first went to the North or South pole, they were outfitted with supplies for months they had to carry or pull with sleds. Hundreds of years before that, Columbus and Magellan set out to sea also with provisions for months for ships (for hundreds of crewmembers). They survived more than 3 months without re-provisioning, because they prepared expeditions that didn't require it.

The NASA study has 9.8 tons of food canisters for the 6 person crew. For 900 days, that's 1.8 kg of food per day per person (~4 pounds). Water is currently being recycled on the ISS right now. I suppose the question is shielding, but I'm pretty sure that just requires MOAR shielding. So we have food, water, oxygen for 3 years, climate control (PV powered), waste facilities, and shielding. What else is needed for life support?

With respect Soda, your missing the bigger picture

Do a chemical mission to Mars which is pushing the technology we currently have to the very ragged edge and then what ?

Nothing

There is nowhere else to go with that technology

That's the problem

Without NTR there is simply no future for a manned space programme

[Soda Popinski]

With respect Soda, your missing the bigger picture

Do a chemical mission to Mars which is pushing the technology we currently have to the very ragged edge and then what ?

Nothing

There is nowhere else to go with that technology

That's the problem

Without NTR there is simply no future for a manned space programme

I'm not missing the bigger picture. I'm ignoring it. The topic of the thread was whether current technologies could be used to get to Mars and the outer planets. I agree with you that's a no with the outer planets (excluding NTRs).

I'm not asking what the point is, but if it's possible.

[EpicRootHairCell]

Step.1 develop a set of self replicating robots that can mine the surface of the moon and make copies of themselves.

Step.2 deploy a few of these to the lunar surface

Step.3 once the population has increased to a set level limit reproduction to maintaining the population and get them to start building the rocket on the moon. I would be politically acceptable to make a nuclear thermal rocket or nuclear powered electric engine on the moon from fuel gathered on the moon. As you have a free access to material, fuel and construction you can build a simple massive rocket with a very large amount of delta v allowing short transit times and a centrifuge type system to keep people happy.

Step.4 launch the rocket from the moon and launch a series of rockets from the earth into lunar orbit carrying the food and crew to the rocket in orbit around the moon.

Step.5 set off and have a short transit time

Step.6 land using a chemical rocket

Step.7 return to orbit. dock with the main craft and fly home on a chemical rocket for political reason

Step.8 repeat a few times to get people happy with nuclear reactors in space and then for future missions use a nuclear rocket on the way home as well

bobs your uncle

[Top8]

Totally agreed on the Lunar infrastructure origin. Thinking beyond just doing a "mission" the only things we should be launching from Earth are people and small payloads of sophiticated hardware that can't be manufactured with the Lunar infrastructure. Though given the difficulties of getting on and off the moon automated assembly stations in lunar orbit - even a small human presence to allow for highly technical work being done efficiently - is the way.

If it helped the assemly could even be done in earth orbit. With automation keeping the other costs down then a focus on using a system like http://www.stratolaunch.com/ could provide economies of scale.

The idea is to stimulate an effective eonomy in space. You can have technology far better than is required and without an economy the "mission" approach will result in no long term presence.

EDIT: That all said, NTR or LFTR + Emag will be the rocket propulsion of choice in space.

Edited February 2, 2014 by Top8

[Nuke]

i figure once you have a base, some small scale agriculture (underground hydroponic farms), a mining operation (metals, gravel, water), a foundry, a water purification and electrolysis facility, and a nuclear reactor to power it all. you could build an entire self sustaining lunar city around just that. going to mars is just a publicity stunt, when the get back we still wont have anyone living beyond leo and we still wont have any infrastructure for going elsewhere.

EDIT: That all said, NTR or LFTR + Emag will be the rocket propulsion of choice in space.

at least till we get polywell+mpd.

Edited February 2, 2014 by Nuke

[Top8]

at least till we get polywell+mpd.

Good point - though I have not heard much at all about polywell lately. It would be great but it seems like something advertised as so striaght forward should already be out there and running

[architeuthis]

I get it. It's too expensive.

The proposed NASA chemical rocket based missions is 12 launches, totaling 796.2 (table 4-2). That will be assembled in LEO with 12 launches. Expensive, yes, but technologically possible (which is the point of the thread). Again, the ISS took 32 launches, also in LEO. So 12 launches seems technically possible to me.

So I'll concede it's expensive, and we'll never do it using our current technologies, due to budgetary and political reasons.

Simon is making a practical argument, I fully agree that we will probably never see a manned Mars mission using chemical rockets alone. For instance SLS (assuming it is built) will have less than half the payload to orbit of the Ares V, so make that 24 launches for sake of argument. Currently they plan on launching them at a rate of 1 every other year. Therefore 48 years to build the Mars fleet. And this assumes zero losses to cryogenic boil off (i.e. indefinite storage of liquid H2 in space), a technology which is as yet undeveloped.

So technologically possible, in theory perhaps. But in realty? I do not think so.

Edited February 2, 2014 by architeuthis

[Rakaydos]

It seems like the major stumbling block for a chemical mars mission is the expence of the large number of launches needed to build the craft, right?

What if the cost of a launch could be dramatically reduced? like, dollars per pound cheap?

One of the most interesting launcher proposals I've seen isnt a rocket at all- it's a chain of airships (designed for lower and lower pressures) that tranship cargo to low earth orbt over the course of about two weeks. The final stage is a multi-kilometer aerodynamic gasbag that could never survive winds near the surface, but never drops below the edge of the atmosphere. After receving cargo from the previous airship stage, it uses a high ISP low thrust system (plsma drive of some kind?) to move the airship.

As the airship speeds up, it generates aerodynamic lift, which reduces atmospheric pressure, which reduces drag, which permits a higher top speed. At a certian point, you can replace "aerodynamic lift" with "orbital velocity", as you slowly work your way up to low earth orbit.

[Nuke]

^ you got a source for that, it sounds interesting.

Good point - though I have not heard much at all about polywell lately. It would be great but it seems like something advertised as so striaght forward should already be out there and running

emcc website is back up and claims they are working on wb8, which is phase 2 of a 3 phase plan where phase 3 results in a breakeven reactor. i believe they are funded through phase 2. the problem with polywell is that the us navy is footing the bill, and they want a little bit of secrecy. as a result they dont want any papers to be published on polywells. bussard had this problem when he was still alive. but so long as the science is being funded i dont mind it being a little secret. several other science teams are testing polywells, but i dont think they are as far along as emcc (at the very least they are confirming some of bussard's findings).

Edited February 2, 2014 by Nuke

[Rakaydos]

http://jpaerospace.com/ for the Airship to Orbit program.

They're a bit slow updating, and they're early in the "learning to build edge-of-atmosphere loading docks" stage.

(while they're at it, they offer "near space experimental payload space" to thousands of students, as long as their experiments fit in pingpong balls they dump in a hopper on their lifters)\

Edit: they moved their regular updates to facebook, it looks like: https://www.facebook.com/jpaerospace?sk=wall

Edited February 2, 2014 by Rakaydos

[maccollo]

Simon is making a practical argument, I fully agree that we will probably never see a manned Mars mission using chemical rockets alone. For instance SLS (assuming it is built) will have less than half the payload to orbit of the Ares V, so make that 24 launches for sake of argument. Currently they plan on launching them at a rate of 1 every other year. Therefore 48 years to build the Mars fleet. And this assumes zero losses to cryogenic boil off (i.e. indefinite storage of liquid H2 in space), a technology which is as yet undeveloped.

So technologically possible, in theory perhaps. But in realty? I do not think so.

Or, instead of pulling a number out of the blue, we could look at the launch manifest in the design reference mission. http://www.nasa.gov/pdf/373665main_NASA-SP-2009-566.pdf

On page 27 you will find the launch manifest for NTR, and on page 29 you will find chemical.

The NTR plan uses 9 Ares V launches while the chemical plan uses 12 launches. You will notice however, that the heaviest payload is "only" 108.5 tons.

This sounds pretty doable with SLS block 2, which will come into service sometime between 2020 and 2030. In fact, with a few optimizations it might be doable with the 105 ton 1A.

SLS production rate figures appears to range between 2 per year, to once every 4 years, the later obviously making the whole thing impossible. But at 2 per year, this still poses a problem for this plan which requires one HLV launch every 30 days.

I don't think they can just stack these in the corner of the VAB until it's time for launch.

But of course this wont happen until like 2040, probably later, maybe never. A lot can change in that time. Perhaps there wont be a manned space program at all.... I am such an optimist.

Edited February 3, 2014 by maccollo

[Simon Ross]

I get it. It's too expensive.

The proposed NASA chemical rocket based missions is 12 launches, totaling 796.2 (table 4-2). That will be assembled in LEO with 12 launches. Expensive, yes, but technologically possible (which is the point of the thread). Again, the ISS took 32 launches, also in LEO. So 12 launches seems technically possible to me.

So I'll concede it's expensive, and we'll never do it using our current technologies, due to budgetary and political reasons.

I still think it's technologically possible, as I disagree with the life support issue. The ISS needs resupply every 3 months because it's designed to be resupplied every 3 months.

3 years is a lot. But they don't need to bring all 3 years worth of supplies and life support. The In-Situ Resource Utilization plants will make the water and oxygen for their stay on the surface (and possibly the return trip). So they need to bring water, oxygen for the 400 days there and back, and food for the entire 900 days.

If you look a hundred years ago, when people first went to the North or South pole, they were outfitted with supplies for months they had to carry or pull with sleds. Hundreds of years before that, Columbus and Magellan set out to sea also with provisions for months for ships (for hundreds of crewmembers). They survived more than 3 months without re-provisioning, because they prepared expeditions that didn't require it.

The NASA study has 9.8 tons of food canisters for the 6 person crew. For 900 days, that's 1.8 kg of food per day per person (~4 pounds). Water is currently being recycled on the ISS right now. I suppose the question is shielding, but I'm pretty sure that just requires MOAR shielding. So we have food, water, oxygen for 3 years, climate control (PV powered), waste facilities, and shielding. What else is needed for life support?

With respect Soda, but the whole point of the ISS was to test extended human habitation in space.

Given that you would have at the very least expected the station to replicate an extended flight mission in terms of life support, generating an artificial gravity environment etc...

None of that happened

As I have already stated, if we cannot build a life support system capable of 3 years independent operation 250 miles above our heads, how in heck can we have any confidence that we can build one for a Mars mission ?

[Ralathon]

With respect Soda, but the whole point of the ISS was to test extended human habitation in space.

Given that you would have at the very least expected the station to replicate an extended flight mission in terms of life support, generating an artificial gravity environment etc...

None of that happened

As I have already stated, if we cannot build a life support system capable of 3 years independent operation 250 miles above our heads, how in heck can we have any confidence that we can build one for a Mars mission ?

Can't the ISS last for 6 months or so without resupply runs? It isn't as if the Life support system catastrophically fails after that either, it just runs out of supplies. If you had a bigger supply it should last for 3 years. Launching the life support supplies in bigger tanks is a rather pointless exercise, since you're sending up new experiments all the time anyway.

This is like saying that you drink a bottle of water per 5 kilometers of running. This doesn't mean you cant run 10 kilometers, it just means you need more bottles.

[Simon Ross]

Can't the ISS last for 6 months or so without resupply runs? It isn't as if the Life support system catastrophically fails after that either, it just runs out of supplies. If you had a bigger supply it should last for 3 years. Launching the life support supplies in bigger tanks is a rather pointless exercise, since you're sending up new experiments all the time anyway.

This is like saying that you drink a bottle of water per 5 kilometers of running. This doesn't mean you cant run 10 kilometers, it just means you need more bottles.

That would be very true if it was only a bulk supply issue.

Unfortunately an awful lot of LS hardware has also had to be swapped out over the years.

Again, you run into the issue of redundancy on any extended flight, something we really have not solved yet

[Soda Popinski]

Can't the ISS last for 6 months or so without resupply runs? It isn't as if the Life support system catastrophically fails after that either, it just runs out of supplies. If you had a bigger supply it should last for 3 years. Launching the life support supplies in bigger tanks is a rather pointless exercise, since you're sending up new experiments all the time anyway.

This is like saying that you drink a bottle of water per 5 kilometers of running. This doesn't mean you cant run 10 kilometers, it just means you need more bottles.

Exactly my point. The ISS isn't designed for 3 years unassisted survival. So Simon is arguing a false premise. As Ralathon suggests, bring more supplies. And as I keep saying, the current Mars plan involves having 2 years worth of water and oxygen already there before the crew even leaves Earth orbit.

Edited February 5, 2014 by Soda Popinski

[Kryten]

Exactly my point. The ISS isn't designed for 3 years unassisted survival. So Simon is arguing a false premise. As Ralathion suggests, bring more supplies. And as I keep saying, the current Mars plan involves having 2 years worth of water and oxygen already there before the crew even leaves Earth orbit.

Enough water and oxygen for a trip for that length would be practically impossible to launch; even the ISS has to generate oxygen and recycle water. Both systems have failed severely enough to require replacement of major parts, along with the thermal control system.

[Simon Ross]

Enough water and oxygen for a trip for that length would be practically impossible to launch; even the ISS has to generate oxygen and recycle water. Both systems have failed severely enough to require replacement of major parts, along with the thermal control system.

Kryten

Your 100% correct.

NASA is actually pretty closed mouthed about the number of in situ repairs and replacements that have had to be conducted to the ISS, we only hear about the major ones.

So, seriously, does NASA have the experience to launch a 3 year unsupported mission to Mars ?

Does it heck !

If we cannot build a closed system to support a structure 250 miles up we have no chance of doing it 35 million miles away

[Soda Popinski]

Enough water and oxygen for a trip for that length would be practically impossible to launch; even the ISS has to generate oxygen and recycle water. Both systems have failed severely enough to require replacement of major parts, along with the thermal control system.

Which is why they won't launch 2 years of oxygen and water. The plan is to launch the In-Situ Resource Utilization Plant , a nuclear or solar powered system to extract oxygen from the Mars atmosphere to make oxidizer for the ascent fuel (methane brought from Earth), breathing oxygen, and water (I think combined with Earth sourced hydrogen).

Geez, it's almost as if nobody is bothering to read the 384 page NASA Mars Reference Architecture 5.0 link I keep mentioning.

Note, I accidentally linked to the shorter 100 page version originally.

[Soda Popinski]

If we cannot build a closed system to support a structure 250 miles up we have no chance of doing it 35 million miles away

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.