# Mission to Mars



## J-Sun (Dec 4, 2014)

"...half a loaf with a side of bacon..."





(BTW, the mission which was scheduled for this morning was scrubbed and rescheduled for tomorrow.)


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## J-Sun (Dec 6, 2014)

C'mon, people! Space! 

Success!

(I don't know why the board won't let me embed time-indexed youtube links but the above link will take you to the c.1 minute report from five-some to six-some of the news summary.)

There was no human in it, of course, but there is something cool about it being the farthest we've gone since 1972 with a vehicle that hopefully *will* have a human in it. The jobs numbers show us clawing out of the hole in the economy and hopefully we can claw out of the hole in our space program as well. (When I say "our" in stuff like this, I'm of course mostly referring to the US but referring to everyone with any similarities, especially when it comes to space.)


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## Parson (Dec 6, 2014)

It was great to see a major rocket blast off again, and with a really appealing long term goal. But my opinion is that if we want to be really serious about interplanetary travel, we are going to have build the ship in space so that it can used and re-used over and over again. Lifting a really serious payload out of our gravity well is just not a long term solution.


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## Ray McCarthy (Dec 6, 2014)

We need a Space Dock as replacement for ISS. It can do the ISS stuff too.  Perhaps also a final fit out dock in a Sun Synchronous orbit (un-interupted solar power, but much "higher" orbit).

It will be interesting to see what  Indians and Chinese do. Currently ESA is maybe a little ahead of NASA and the US independents, and they warn that the Chinese are only "ten years behind".

A joint Russian, European  & USA Mars mission isn't impossible, despite the current tension with Russia (someone suggested the Russian difficulties are caused by lack of understanding about Geography). USA is depending for a few more years on Russian Soyuz, the Russian's main space port is now inconveniently in Kazakhstan, which may be why they have a pad now in the European Space Port. 

Only the Chinese and Russians currently have vehicles they use confidently to put people in space. But Europe, Japan and India could if there was a budget. US looks like it will in a couple of years.

The current Orion capsule test used an  old US launcher. A new US launcher will be used. The Ariane  five isn't rated for people, I don't know about Ariane six (just approved for development). Soyuz uses a Russian launcher. The Russians also sometimes use Ariane for satellites and  ESA / Arianespace sometimes use Russian launches.

CNES is French version of NASA. No-one has anything like ESA (Canada is associate member, EU funds a little more than 20% and the actual members are a mix of EU and non EU, i.e. includes Switzerland and Norway). Arianespace is a separate company mainly created by ESA as world's first (and most successful Space Launch organisation), if SpaceX, Virgin Galactic, Boeing etc put Arianespace out of business by under cutting prices, ESA would still exist. The vast majority of Arianespace shares are owned by French and German companies. French companies and organisations combined are largest shareholders.

http://en.wikipedia.org/wiki/CNES
http://en.wikipedia.org/wiki/European_Space_Agency
http://en.wikipedia.org/wiki/Arianespace

Most non-techicnical people are unaware of CNES, ESA and Arianespace. The European space organisations are major contributors to ISS and Orion and building the only civilian GPS system (The US & Russian Presidents can disable civilian use of their systems in a instant. Most Mobile phone base stations, Digital TV and Digital Radio Transmitters as well as personal navigation products in the West depend today on the US GPS, which is a Military system).


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## mosaix (Dec 6, 2014)

Great to them back in the 'manned space flight' business again.


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## Nick B (Dec 7, 2014)

As the parson says - rockets are not the way forward, they are a step sideways. Maybe thats better than no step at all but it isnt going to make us a truly spacefaring race. 
To get serious we need, as Ray says, a permanet station that can serve as a dock and shipyard. 
Surely building a craft that is only designed for space, with no requirement for getting off or on planets would be easier, from an engineering point of view.
 At least from that point on you have a base to work from.


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## BAYLOR (Dec 7, 2014)

Im glad the we're back in space and Orion was a success. But I think we're still a few years away from a manned Mars mission.


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## J-Sun (Dec 8, 2014)

Here's a more detailed writeup of the test flight.

I agree with everyone that we need permanent stations (and asteroid mining and all sorts of space infrastructure to not just handle Mars but, ultimately, the stars) but right now, I'll just settle for not having to hitch rides with the Psoviets and for at least pretending to aim at something outside of Near Earth Orbit.

Like the guy in the first clip said, going off half-cocked with a bad plan can waste a lot of money but hopefully we can fake it 'til we make it. Doing nothing obviously just does nothing.

As far as the timing, Baylor, they're not even pretending this will get done until the 2030s. If we really said "this nation should commit itself to achieving the goal, before this decade is out[1], of landing men and women on Mars and establishing a permanent presence there" then we probably could but, otherwise, I think even the 2030s is optimistic the way this seems to be going.

[1] Meaning 2024 since there isn't as much decade left as there was in 1961 when the original of my paraphrase was uttered.


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## markpud (Dec 9, 2014)

I'm hopeful that a manned Mars mission is possible, but the radiation, not to mention the boredom of such a journey and the one-way factor don't make for an appealing process. People liken it to the risks taken to explore the "new world" across the Atlantic, but at least those guys could breathe unaided and find things to eat. 

But there will be some intrepid souls prepared to make this long journey and plant that flag in the ground, then those who follow will know what's in store at least.

For now, I'm just waiting for commercial space flights to become established and hopefully affordable in my lifetime! I think any permanent presence on Mars is still a Century away.


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## scientia (Dec 25, 2014)

Parson said:


> But my opinion is that if we want to be really serious about interplanetary travel, we are going to have build the ship in space so that it can used and re-used over and over again. Lifting a really serious payload out of our gravity well is just not a long term solution.


I'll ask the obvious question. Where exactly would you get the materials to build this spaceship without lifting them out of Earth's gravity well?


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## Abernovo (Dec 25, 2014)

I believe Parson is thinking in the long term, scientia: that we need to establish bases and colonies off Earth, where the materials can be mined.

So, to answer your question, from asteroids, from the Moon, and from Mars. The last two would still need the materials to be lifted from the surface into orbit, but the delta-v and costs would be significantly less than from Earth.

Yes, it would be expensive to establish these off-Earth bases, but the _long_-term returns should justify the costs. Once the first few were built, later ones (and any long distance spaceships) would be built outwards from them. And, considering the recent successes on Mars and landing on comets, there's a good argument that some of the mining (and transport) could be handled remotely, with robots doing a lot of the manual labour.


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## scientia (Dec 25, 2014)

Ray McCarthy said:


> We need a Space Dock as replacement for ISS. It can do the ISS stuff too.  Perhaps also a final fit out dock in a Sun Synchronous orbit (un-interupted solar power, but much "higher" orbit).


Where are your numbers for vehicle mass, transfer fuel, the Mars lander and its fuel weight? Your description is essentially the plan that Von Braun had for a Lunar mission. It wasn't practical so it was rejected in favor of a single launch vehicle. I know where Von Braun's numbers came from. They were based on the lifting capability of a rocket in the Saturn 1B class which was 1.3 million lbs and 46,000 lbs to LEO. With that kind of lift, you would have needed one for the lunar module, one for the service module, and another to lift the third stage



> It will be interesting to see what  Indians and Chinese do. Currently ESA is maybe a little ahead of NASA and the US independents, and they warn that the Chinese are only "ten years behind".


That's a fantasy if I ever heard one. Let's get the basics down. The vehicles that currently exist that can do 40,000-60,000 lbs to LEO are the Atlas V, Ariane 5, Titan IV, Delta IV Heavy, and Proton. India just reached this goal about a week ago with the first launch of LVM3. China might match this capability next year with Long March 5.

So, that sounds roughly equal if China delivers Long March 5 next year. The problem is that next year, the US will test Falcon Heavy which doubles this to 117,000 lbs LEO. This will then become the heaviest launch vehicle. The ESA has plans for an Ariane 6 some time in 2021. However, by 2018, the US will have SLS with a design lift capability 150,000 lbs and then SLS 2 in 2021 with of 290,000 lbs. There is nothing else currently in development.

The older designs are obviously Saturn V and Energia. We would have no reason to duplicate Saturn V since it is surpassed by SLS. I suppose the Soviets could create another lift vehicle heavier than Proton if they wanted to since they do have the RD-170 engine.



> A joint Russian, European  & USA Mars mission isn't impossible, despite the current tension with Russia (someone suggested the Russian difficulties are caused by lack of understanding about Geography). USA is depending for a few more years on Russian Soyuz, the Russian's main space port is now inconveniently in Kazakhstan, which may be why they have a pad now in the European Space Port.


It looks like the earliest for a manned US replacement would probably be 2017 with CST-100. However, Dragon V2 could possibly be ready in 2016. The main reason the US has chosen to Soyuz is the cost. And this cost probably won't get much less for US launch until they are using Falcon 9 (which would need CST-100). For unmanned missions, the US already has the Dragon resupply vehicle.



> Only the Chinese and Russians currently have vehicles they use confidently to put people in space. But Europe, Japan and India could if there was a budget. US looks like it will in a couple of years.


That depends if you are talking about the lifting rocket or the crew module. The US has lifting rockets but no current crew module. There are seven different US manned crew vehicles being talked about now. I only mentioned CST-100 and Dragon V2 since these seem to be on track. There is no current demand for Orion which is a long duration vehicle. The nearest term mission has been the lunar asteroid mission in 2021. But let's put this in perspective. China has a grand total 6 manned flights with Shenzhou which is what the US had in 1963. The Russians in contrast are on their fourth generation of Soyuz. Theoretically, Shenzhou is good for 20 days and Soyuz for 30 days. This is a little better than the 14 days for the 40 year old Apollo Command/Service Module.



> The current Orion capsule test used an  old US launcher. A new US launcher will be used. The Ariane  five isn't rated for people, I don't know about Ariane six (just approved for development). Soyuz uses a Russian launcher. The Russians also sometimes use Ariane for satellites and  ESA / Arianespace sometimes use Russian launches.


Delta IV Heavy has been around since 2004. It is currently the heaviest lift launcher in existence with over 63,000 lbs to LEO. Russia's heaviest lift is Proton with 49,000 lbs but it isn't man-rated.



> Most non-techicnical people are unaware of CNES, ESA and Arianespace. The European space organisations are major contributors to ISS and Orion


That depends on what you mean. The original Apollo vehicle had a Command Module and a Service Module. What was tested would be equivalent to both of these. The part that holds people is now called the Crew Module so it still has the same initials. But, it's about 50% larger in volume and mass than the Apollo CM. It was developed by NASA.

The ESA developed the Service Module for Orion which is somewhat equivalent to the Apollo Service Module. The Orion SM has solar panels and can supply twice as much power as Apollo SM. The Orion SM is also capable of recycling water which is something Apollo didn't do. However, the big difference is weight. Orion SM is only half the mass of Apollo SM. This is because Apollo had a 91,000 Newton engine with 40,000 lbs of fuel. Orion SM only has 2,000 Newtons of thrust and 18,000 lbs of fuel.


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## scientia (Dec 25, 2014)

Abernovo said:


> I believe Parson is thinking in the long term, scientia: that we need to establish bases and colonies off Earth, where the materials can be mined.


Really? You plan to mine iron and aluminum on the moon?



> So, to answer your question, from asteroids, from the Moon, and from Mars. The last two would still need the materials to be lifted from the surface into orbit, but the delta-v and costs would be significantly less than from Earth.


You are going to go to Mars to try to set up a mine to get materials to build a spaceship to go to Mars? I think there is a step missing in there somewhere. Also, the delta-v needed to get materials from an asteroid is a lot more than it takes to lift them from Earth. And, that would be assuming that you had somehow built refinery, processing, and manufacturing facilities for these materials.



> Yes, it would be expensive to establish these off-Earth bases, but the _long_-term returns should justify the costs. Once the first few were built, later ones (and any long distance spaceships) would be built outwards from them. And, considering the recent successes on Mars and landing on comets, there's a good argument that some of the mining (and transport) could be handled remotely, with robots doing a lot of the manual labour.


Okay. Let's say that you have somehow set up a base on Mars. Where would you get fuel to provide heat and electricity?


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## Abernovo (Dec 25, 2014)

scientia, I don't have all the answers. I also don't think there's any need for sarcasm.

As you seem from your words to be looking for a fight, and I'm not interested, I'll bow out of this.


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## BAYLOR (Dec 25, 2014)

scientia said:


> Okay. Let's say that you have somehow set up a base on Mars. Where would you get fuel to provide heat and electricity?



Putting the base underground would be helpful, That would insulate it from the cold and lessen the amount of energy needed for heat . It would also provide protection from solar radiation. 

Solar panels could provide some of the heat energy and yes Im well aware that Mars gets about half the sunlight earth gets but we can come up with solar  panels that can do more with less.

Portable hydrogen fuel cells could do it as well.


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## chrispenycate (Dec 25, 2014)

I'm in favour of a spaceplane solution, style Skylon. The advantage of asteroid material is that the ∂v can be applied over a long period of time, and if you really do want high accelerations nobody complains about you mucking up the environment with a fusion explosion - out of an atmosphere you have to get your first lumps up to orbital speed, if not escape speed (Why do people use the vector term, escape velocity? The direction's pretty well irrelevant, unless it intercepts the planet/star/oh, all right moon/planetoid in question.) before friction undoes all your good work - very inefficient. 

Perhaps we could crash a few comets onto the surface of Mars, increasing scarce volatiles and adding energy at the same time. Preferably before the colonists arrive.

For a smallish population in sealed habitats, domes or tunnels, there is plenty of energy available. No petrolium, obviously, nor logs - none of the simple sources our ancestors relied on. But, for a few hundred inhabitants, quite adequate. It's when we get hundreds of thousands, millions that we need fusion power or something, just to grow the plants. And we need at least one orbital station round Earth (a serious one, hundreds of crew) and a permanent one round Mars, too, before transfer becomes practical. And likely a string of satellites so they have permanent contact with Earth, and continuous internet.


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## Parson (Dec 26, 2014)

I was thinking in the long term, but not that long term. I was thinking of assembling a true space ship in earth orbit. The mining and raw materials are lifted out (unfortunately) of the earth's gravity well. It could then be powered by something more in the line of an ion drive which could be refueled when necessary at far smaller penalties.


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## BAYLOR (Dec 26, 2014)

Parson said:


> I was thinking in the long term, but not that long term. I was thinking of assembling a true space ship in earth orbit. The mining and raw materials are lifted out (unfortunately) of the earth's gravity well. It could then be powered by something more in the line of an ion drive which could be refueled when necessary at far smaller penalties.




It could take close to a year to get there . You'd have to build a substantially big craft that could hold enough food, water and air for the journey.  You'd also need a life support system that could recycle both the air and water . Then there the issue of lack of gravity on the human body , this could cause some problems  like loss of bone mass and muscle atrophy.  And how safe would the ship and its crew be from radiation and micro-meteorite fragments.?


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## Parson (Dec 27, 2014)

I don't have the math to figure this out precisely, but if we could achieve a consistent .1 gravity for thrust, I believe that a flight to Mars would only take a few weeks, not nearly a year. But there would still be all kinds of difficulty with radiation even when on Mars. The only safe place would be under the ground.


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## Vertigo (Dec 27, 2014)

I may be wrong about this and have only found limited support for my 'belief' online but...

I'm sure I heard that the planned manned mission to Mars _will _be assembled in orbit and not launched complete from the surface. The confusion comes, I think, from the use and testing of the Orion capsule. Orion is not solely intended for a mission to Mars. It is designed for any missions beyond Earth orbit including near Earth asteroids, possibly even the moon, possibly even serving the ISS, _and eventually _Mars. However the capsule has only 2.25 cubic meters living space per crew member and for longer missions more is needed. So for deep space missions a DSH (Deep Space Habitat) will be used in addition to the Orion Capsule. Current plans are for this capsule to have in the order of 70 cubic metres of living space per crew member (stop and think for a minute just how much bigger this makes the DSH compared to Orion) and the Orion capsule would effectively just be the command module. There is no way something that big is going to be launched from the surface along with the Orion Module in one operation; it will have to be assembled in orbit and launched from there. And my understanding from, I think, an Horizon documentary a few months back is that that is what is planned.


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## chrispenycate (Dec 27, 2014)

If gravity is a major problem you could build it in two bits held together with string, rotating round their common centre of gravity, simulating it. And leave the entire setup in Mars orbit, minimally inhabited, for an emergency evacuation potential. 

Parson, unless we are going for atmospheric braking most of the propulsion would not be in getting there, but matching speeds, which explains the extra time. Yours was for getting to where Mars was when you arrived, not to be travelling on the same vector. (Of course, atmospheric braking is an option, even achieving a stable orbit, but I do have to wind in the string between the halves of my ungainly craft {and store the spin on a gyroscope; I'm going to need it for the orbital.} Unless one of the two segments was the lander, in which case, give me a few minutes to work it out…)

Outside the Earth orbital region, where the junk is concentrated, micrometeorites can be more or less ignored - statistically too unlikely to make a fuss about except in SF films - but solar flares are unpredictable, and carrying enough mass to make up shielding, even if said mass is reaction fuel, slows us right down.


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## Parson (Dec 28, 2014)

chrispenycate said:


> If gravity is a major problem you could build it in two bits held together with string, rotating round their common centre of gravity, simulating it. And leave the entire setup in Mars orbit, minimally inhabited, for an emergency evacuation potential.
> 
> Parson, unless we are going for atmospheric braking most of the propulsion would not be in getting there, but matching speeds, which explains the extra time. Yours was for getting to where Mars was when you arrived, not to be travelling on the same vector. (Of course, atmospheric braking is an option, even achieving a stable orbit, but I do have to wind in the string between the halves of my ungainly craft {and store the spin on a gyroscope; I'm going to need it for the orbital.} Unless one of the two segments was the lander, in which case, give me a few minutes to work it out…)
> 
> Outside the Earth orbital region, where the junk is concentrated, micrometeorites can be more or less ignored - statistically too unlikely to make a fuss about except in SF films - but solar flares are unpredictable, and carrying enough mass to make up shielding, even if said mass is reaction fuel, slows us right down.



Which makes it clear that I had absolutely no advanced Physics in school. But does that added time add up to a year in transit at a steady .1 gravity acceleration? Would the fastest transit time then include a gravity assist from an orbit around the sun? (Don't strain yourself if this takes some really involved calculations. I'm interested but not interested in making you do something you don't really want to do.)


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## Dennis E. Taylor (Dec 29, 2014)

Parson said:


> Which makes it clear that I had absolutely no advanced Physics in school. But does that added time add up to a year in transit at a steady .1 gravity acceleration? Would the fastest transit time then include a gravity assist from an orbit around the sun? (Don't strain yourself if this takes some really involved calculations. I'm interested but not interested in making you do something you don't really want to do.)



You'd be amazed at how quickly you can get somewhere at constant acceleration. Let's work it out.

The formula for distance traveled for a given acceleration and time is D=.5*a*(t^2) .
You can solve for time and you get t=(2d/a)^.5
The closest the Earth and Mars ever get is 35,000,000 miles. It's an oversimplification, but let's work out how long it would take to travel that distance.
First, divide the total distance by 2, since you accelerate for the first half and decelerate for the second half.
17,500,000 miles.
Everything has to be in the same units. 1 G is 32 feet per second squared, so .1 G is 3.2 ft/s^2
17,500,000 miles is 92,400,000,000 feet. So using the formula t=(2d/a)^.5 you get 240,312 seconds or 66 hours. Double that for the entire trip, and it's 132 hours door to door. 5.5 days. At midpoint, you'd be travelling about 145 miles per second.

The thing is, there's so much variation in the starting and ending points, velocities, positions in orbit, etc, that you could claim a total trip time anywhere between a week and maybe a month as long as you didn't get specific.


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## Mirannan (Dec 29, 2014)

Regarding the building of stuff in orbit (and fuelling it, which is far from trivial) one of the problems IMHO with the current approach is the blanket safety obsession of NASA.

To explain further: While great attention to safety is obviously reasonable in the case of astronauts and high-value cargo (spaceprobes and comsats come to mind) there are two problems with it. The first is that, arguably and I have seen the argument made, too much attention is being paid to safety in the case of astronauts. After all, all pioneers throughout history have had their casualties and the death rate in the early days of aviation was horrific. And one of the best ways, in the long run, of making any activity safer is to do more of it.

The second, and much less controversial, point is that all cargoes are being treated the same. A large part of the cost of a rocket launch is related to the obsessive safety standards. I think it's reasonable to use less comprehensive standards when lifting cheap, easy to replace stuff - things like food, fuel, water and structural beams. Cost analysis ought to be applied, and maybe some of the checks omitted, when lifting such cargoes; how much does it really matter if one tank of LOX in twenty is lost at launch, when eliminating that possibility doubles the cost?


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## Ray McCarthy (Dec 29, 2014)

Mirannan said:


> Regarding the building of stuff in orbit (and fuelling it, which is far from trivial) one of the problems IMHO with the current approach is the blanket safety obsession of NASA.


I don't know that "safety concerns" add a lot or anything to cost. Bureaucracy and poor procurement, US Defence Industry structure perhaps.

Regarding in Orbit construction there are four aspects:
1) Building something larger than can be launched on a single reliable rocket
2) Launches fail. So having 20 to 400 launches means when a launch fails you lose less.
3) The final structure can be too large for single launch.
4) The structure need not withstand the stresses of high G launch.
5) The big advantage is for a Spacecraft that does multiple round trips as you then only lift the parts once.

Orbital assembly has no lift cost saving advantage for single use craft. All Spacecraft beyond Earth Orbit so far have been single use.

The cost of a Launch to resupply ISS is far more than the materials. It's only high end communications satellites that are worth more than a Launch.
I have an out-of-date list of Satellite and Launch costs someplace.



Mirannan said:


> The second, and much less controversial, point is that all cargoes are being treated the same.


They are not. Humans and Cargo use different launchers for ISS.
Newer unproven Launchers were used for non-critical ISS materials.
They also have reserves in case a launch fails.

A really decent reusable Nuclear* powered high thrust Ion Drive Spaceship would need 50 to 400 launches depending on the amount of power, reaction mass (water instead of Xenon) and length of Linear Accelerator to "juice up" the power of the Ion Drive. Sadly other than a Generation Ship (which would have to be about x10 more launches) we have no idea how to build a Starship. Oxygen, food, recycling are all solved on stealth submarines and also verified on ISS.

(*i.e. like current submarines, not even Fusion power, which need not surface over a year and use the Nuclear reactor to make oxygen from water)


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## Ray McCarthy (Dec 29, 2014)

Bizmuth said:


> You'd be amazed at how quickly you can get somewhere at constant acceleration.


I wouldn't.
All current trips are mostly coasting with no thrust. There are even very slow circuitous routes to reduce the needed initial and final thrusts more.

It turns out that even if you use Fusion power the maximum time possible on a reasonably high constant acceleration (to simulate gravity) is about 6 months (3 months accelerate, 3 months decelerate). Unless you in advance put caches of reaction mass / fuel en-route, or can pass by comets and recycle the water in them. So without a hypothetical (still fantasy) Hyper or Jump drive any interstellar travel has to be mostly coasting, so only a Generation Ship is currently possible.

With current Nuclear power and higher power than current Ion drives (which have no linear accelerator due to lack of power and space) we can certainly do Mars trip in a few weeks. But the launch cost would be crippling.

So a longer mostly unpowered trip when the solar wind is higher (to reduce Cosmic Radiation) and hope no Solar Flares are likely.


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## Mirannan (Dec 29, 2014)

I was talking about cargo, specifically meaning non-living cargo.

The real point is that even Dragon is subjected to a great number of checks which might be reduced if one was prepared to accept a few losses of low-value cargoes. Obviously, for the commercial space-launch companies (which are still very new, and NASA and its pork-barrel politician sponsors are extremely hostile to) failed launches are a PR disaster as well; but they probably shouldn't be.

You say an ISS resupply launch costs far more than the value of the cargo. You're making my point for me.


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## paranoid marvin (Dec 29, 2014)

In all likelihood with the costs involved in getting man to Mars (and back again) would far outweigh any potential returns (from a commercial perspective). The hazards are great, but possibly not as great as sending man to the Moon in the 60s. Even so, any scientific knowledge from man (opposed to a machine) being sent to Mars don't warrant such a risk. 

At best I could see the possibility a spacestation similar to ISS being buit to orbit the planet, with shuttles used to ferry scientists to labs on the planet's surface when it was safe to do so. Personally I think we will see a manned mission to show that we can do it, but not much more than that. We simply don't have the will (or the money) to do so. And arguably without the scientific advances of WWII technology we may not have been able to get to the Moon until the 80s or beyond.


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## Ray McCarthy (Dec 29, 2014)

Unless you are going somewhere to stay, I think sending semi-autonomous robotic like devices makes more sense.


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## paranoid marvin (Dec 29, 2014)

Far safer ,easier and cheaper to develop machines to go to Mars. In ww2 the technology was developed and in the 50s-80s the cold war ensured there was competition to 'conquer' space. It is only in times of need or conflict (or where there is financial interest) that the required funds are made available to advance technology sufficiently and quickly enough to match ambition.

To send people to Mars and to upkeep any base there would be prohibitively expensive and a constant drain on the economy. With nothing coming back in return, no country could sustain this, especially with no financial recompense. Sure it would be great to see what life may have been like on that planet 5000 years ago, but if it is at the expense of hospitals and schools being built and maintained then there is only one way that an elected government can go.


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## Parson (Dec 30, 2014)

So, if I understand correctly, and thank you *Bizmuth* for the physics primer, an ion drive of which we already have a working sample or two could likely be worked up to produce our one tenth gravity acceleration. This should allow us to make a trip to Mars and return within say 6 months. I making the assumption that you would not have to have a linear accelerator to get the ship in motion. Wouldn't a steady .1 g acceleration overcome inertia? If that's so then we could begin to explore and mine the solar system. The second ship would be simpler and cheaper, as would the next and pretty soon there would be a fleet. And the first wave of human expansion beyond the atmosphere of earth would be on the way. 

Star travel -- Now that would take some very serious advances. And unless the speed of light can be defeated some how, human travel to the stars might always be in the realm of fiction rather than reality.


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## Ray McCarthy (Dec 30, 2014)

You only add Linear Accelerator to an ion drive if you have a massive power source such as the kind of Nuclear Reactor on a submarine, it then reduces the amount of stuff you need to throw out (reaction mass, Xenon on low power ion Drives today) and lets you use plasma from water instead (as well as oxygen for crew).
Current Nuclear powered "robots" and satellites use thermoelectric, not a full sized reactor so are very limited power.

Current Ion drives are very low power as they use Xenon and Solar power, but it's far better than chemical propulsion or compressed gas. 

Any acceleration overcomes inertia. Even 0.01 G acceleration done long enough will drive a spacecraft awesomely fast. There is no air resistance or rolling friction such as limits the speed of a car. 

At the minute a Generation Ship is technically feasible, if financially impossible, unless some physics and maths is discovered, that's as good as it gets. It can't accelerate all the time unfortunately as that would use up all the "reaction mass". Even if 100% conversion of Fusion power to Microwave / Laser propulsion can't run continuously for an Interstellar flight. You'd run out of hydrogen / water. Bigger tanks doesn't solve issue as then you need more thrust for the weight.


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## oorang (Dec 30, 2014)

Ray McCarthy said:


> The European space organisations are major contributors to ISS and Orion and building the only civilian GPS system (The US & Russian Presidents can disable civilian use of their systems in a instant. Most Mobile phone base stations, Digital TV and Digital Radio Transmitters as well as personal navigation products in the West depend today on the US GPS, which is a Military system).



That is absolutely true and probably a good reason to build a private alternative system.  But, realistically, the US could never actually shut off public access to the GPS.  At this point, way too much of our infrastructure depends on it.  Agriculture, for example, relies on it so much that our food production would drastically drop if it shut off.  Shipping is basically GPS-driven these days.  Plus all kinds of random commercial and personal uses.  They'd certainly have to have an awfully good reason at least...


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## Parson (Dec 31, 2014)

oorang said:


> Agriculture, for example, relies on it so much that our food production would drastically drop if it shut off. Shipping is basically GPS-driven these days.



Living as I do in the middle of the Midwestern United States I can say that this is an overstatement. It is true that GPS is used more and more in agriculture, but mostly it tweaks what is already done. Food production would drop, but not drastically, at least not yet.


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## Ray McCarthy (Dec 31, 2014)

oorang said:


> our food production would drastically drop if it shut off. Shipping is basically GPS-driven these days.


Agriculture would hardly be affected.
The GPS issue on ships is overstated and there is an updated LORAN now.
Unexpected things are dependent: Mobile Phone Network, Most  Digital TV (USA, Japan and Brazil possibly not) and perhaps DAB (Not USA HD Radio). These all use GPS as cheap alternative to a local atomic clock, not for positioning at all.

Any major conflict or trade dispute the USA or Russian President can turn off the civilian aspect without any reference to the rest of Government. Only USA 3G /4G would be affected, I think the CDMA the USA has instead of GSM isn't affected and I'm nearly sure USA Digital Radio & TV isn't affected (different system to everyone else). So a likely enough scenario that Europe has started deployment of Galileo as an alternative. Galileo being much newer design gives much greater accuracy too.


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