cargo - just an idea

soph · 2002-12-02 17:45:33

i was on vacation for the past few days, re-reading zubrin, and i thought of something. what if we could have permanently cycling ships delivering cargo between Earth and Mars? I pictured 2 cargo points, and later 3 to 12 (bear with me).

1) A cargo point in Earth orbit and one in Mars orbit. A lift vehicle brings cargo to orbit, deposits it at the "warehouse" and goes back. I pictured Zubrin's rocketplane in this role (I was reading his books, remember). An SSTO would be perfect in this role, especially a scramjet. It could even deliver the cargo while en route to another location on the globe. Several of these deliveries could occur, and a tanker could pick it up, do a throwaround Earth back towards Mars, and vice versa. I pictured an NTR or fusion ship in this role - low fuel needs, and fast travel.

2) Same concept, except cargo points are also put in locations between Earth and Mars, maybe one for each seasonal location (i.e. 3/21, 6/21, etc). This way, the "tankers" could drop off loads of cargo (it's half the distance), and they wouldn't have to wait for the 2 year cycle to occur- they could just drop it off at the most convenient point, and Mars could pick it up within a few months. More loads could be delivered, and relatively small ships are needed (each only needs a minimal fuel content). Since atmospheric launches arent needed, the tankers could be HUGE. Maybe assembled in orbit? (NOT huge orbital hangars, just parts assembled like the ISS).

Ideas, comments, criticism?

Shaun Barrett · 2002-12-02 18:27:26

Hi Soph!

I'm not sure I fully understand all the details of your plan, but the concept of relaying stuff between here and Mars sounds feasible. (To me at least! )

I imagine cargo-carriers from Mars orbit could deposit fuel, mined from Phobos and Deimos, at the 'intermediate' points you mention and return with materials left there by the last Earth vessel. In turn, cargo-carriers from Earth, having deposited their export materials, could load up with that fuel and take it back to Earth orbit to power future trips.

The fuel from the Martian moons, as others here at New Mars have been advocating for months, could make the whole thing much more economically attainable.

It's all a long way off at this stage, I guess, but, as my mathematics teacher always said: "Time spent in reconnaissance is seldom wasted."
It's good to think ahead and speculate a little bit.
Nice one, Soph!!

soph · 2002-12-02 19:00:52

I was wondering-is there any completely safe way to store nuclear fuel through atmospheric delivery (not use, store)? If this could be done, nuclear vessels could be used between planets, since they wouldnt have to be launched from Earth (at least, they wouldnt have to launch themselves), avoiding the environmental and political arguments against nuclear fuel.

Phobos · 2002-12-02 22:26:06

If you mean "completely safe" as in absolutely 100% certain that no failure could ever occur the answer would have to be no. But I think the risk can be brought acceptably low. RTGs for instance are highly durable and have a lot of redundancy as far as safety goes. Not only is the shell harder than hell to crack but the fuel itself is encapsulated in such a way that if the plutonium were released to the environment it would fall in large, insoluable chunks that wouldn't pose a grave respiratory threat and would make cleaning up the released plutonium a lot easier. But of course nothing is fail safe. It just depends on how much risk you can tolerate. Nuclear fuel that isn't intended for immediate use could probably be stored in a fashion similiar to that of plutonium in RTGs.

RobertDyck · 2002-12-03 02:49:18

The Nerva engine was developed specifically as a Trans-Mars Injection stage for a manned mission to Mars. Ground tests were completed to the point where the next test would have been in Earth orbit. That engine was a Nuclear Thermal Rocket. It encapsulated the uranium in ceramic so strong that in the case of catastrophic failure the uranium fuel could fall all the way from space and impact the ground without splitting open. That would leave chunks of nuclear fuel all over the debris field, but each chunk of uranium would be sealed. As for radiation, I have seen video of nuclear reactor workers wearing the same plastic gloves as you get with oven cleaner to poke urnanium oxide powder into steel fuel rods. They just poked the powder in with their fingers. When nuclear fuel comes out of the reactor you don't want to be in the same room, you want a couple feet of lead between you and it, but before it goes in it is relatively safe. Since Nerva would only be turned on after it was safely in orbit, it was already as safe as any other rocket. Nerva was developed from 1950-1974. Timberwind was developed in 1990 and had a slightly higher Isp.

However, environmental and political arguments have little to do with reality.

Tyr · 2002-12-03 07:49:43

I think you have missed the point of cycling stations. To rendesouz with the cycler takes just as much energy and rocket fuel as going there, however, the cycling station is big and roomy, has greenhouses aboard, etc. So all we have to do is take a small fuel efficient rocket to the cycler then travel in comfort. When nearing the destination we board another small taxi and enter orbit while the cycler flies on. The only reason this saves us anything is because the large mass of the cycler doesn't have to be accelerated or decelerated. Cycling stations are no good for cargo-no savings. The best thing would be to use ion drives or solar sails to move cargo from orbit to orbit or Lagrange pt. to Lagrange pt.

TJohn · 2002-12-03 12:41:30

Ion drives is an excellent point. It's been proven and does not cause the environmentalists to worry about doing any damage to the Earth.
That's very interesting post you have RobertDyck! If we could only go back in time and convince the government and NASA to continue with NERVA, imagine where we would be!

soph · 2002-12-03 14:03:37

wouldnt you save energy by avoiding the necessary escape velocity from earth or mars?

Tyr · 2002-12-08 13:32:51

To rendesvouz with the cycler you will still need to reach escape velocity. As the cycler passes Earth it will be moving faster than the Earth is in its orbit around the Sun. You will have to rocket out of orbit at a bit more than escape velocity to match velocities with the cycler. I really wish I knew of a good website about orbital mechanics that would explain this to you.

Austin Stanley · 2002-12-08 17:33:43

Tyr's right.

To do what you propose the spacecraft would have to carry twice as much fuel as it would it need to simply go and stop at mars (using it's engines, not aero-breaking) and much more than to simply get there and come back via a free return orbit. When ever you got to the stopping place, it would have spend essentialy the same amount of energy it has spent to get there to stop, and then spend that amount again to get back.

Here's a good in-depth lesson on orbital mechanics.
http://www.marsacademy.com/orbmect/orbles1.htm

soph · 2002-12-20 18:23:00

alright, ive rethought the idea after reading about the orion ships.

say we've got an orion class mining ship out in the asteroid belt, running on nuclear pulse engines. could we build ships with huge cargo capabilities to dock with the mining ships every few months, and deliver cargo back and forth between mars and the asteroid belt? or would the ship have to come back every time it had to deliver payloads?

soph · 2003-02-28 21:45:59

What about for asteroid belt->Mars/Earth ships? Would cargo points make sense? Refuel in orbit, and go back out to the belt?

John_Frazer · 2003-04-21 18:40:17

Cyclers have been looked at for a long time. The problem is that Orbits of the planets don't line up conveniently. Unless the station/cycler has a lot of Delta-V to burn every orbit, it won't meet a planet every time is comes to the planet's orbit around the Sun.
Any rocket uses lots of propellant to push the station (expecially if it's shielded), and ion drive just doesn't have the thrust to do the job.

One way around this which has been suggested is the Magnetic Sail. It uses solar power for energy, and requires no propellant to be used for maneuvers.

Another comment about this is that the cycler follows Hohman transfer orbits, taking many months on each leg of a trip. Granted, the crews get shuttled to the cycler on cheap taxis, and they spend the trip in full gravity (spin the habs) and full shielding (~hundreds of tons per passenger if using mass shielding, or magnetic sails protect against solar radiation but not cosmic rays).
They're still sitting in a can, waiting for months between destinations.

If we have a fuel production infrastructure in place, to make nuclear pulse rocket thrust-bombs, then it's a few weeks to Mars, 3 months to Jupiter in huge luxury liners.
Either old fashioned fission bomb Orion, or maybe Daedalus or ICAN or the newer "Mini-Orion" if possible.

soph · 2003-04-21 19:15:57

John: I wasn't so much talking about cyclers as freighters, that carry cargo back and forth, never descending lower than orbit.

They refuel on-orbit, so they don't need to stop, and can use a gravity assist to place themselves onto a trajectory for the destination. Orbital rendezvous with a fuel tanker can be timed either prior or during the mission.

I realize that this type of vessel might need to wait for more advanced propulsion systems (perhaps fusion) for application, and that the launch windows would be limited to a ~3-6 month range, but the concept is heavy freighters that can refuel and turn around.

Tyr · 2003-04-21 19:27:54

In space, a freighter could be 95% cargo. A space freighter is much different from an ocean going vessel that must be strong enough to resist the high seas, and the heavier the cargo the heavier the ship. You still need to fire retro rockets or aerobrake to get the cargo into orbit. Now, you could let the 5% that's freighter ship proper just fly on by while the cargo modules fire retros and then aerobrake. I guess that would amount to some efficiency. Solar sails would be great for cargos to and from Mars. A good article is in last month's Moon Miner's Manifesto about that. But why freighters at all? Doesn't Mars have everthing it needs? Or are you planning on selling light elements to lunar colonists?

soph · 2003-04-21 19:37:17

Freighters for people, new supplies, seed factories, power reactors, deuterium transfer, etc.

I was thinking fusion in terms of the speed it could get, probably far surpassing solar in the distance between Earth and Mars.

MarsGuy2012 · 2003-04-22 09:27:29

I would definitely advocate using fusion to power the freighters, but I would still use a Hohmann transfer. You will be able to move much more cargo. They say time is money, but a few months savings probably won't outweigh the extra cargo you can carry with a slower trajectory.

If you're moving colonists to Mars I'd still suggest the six month trip because you can move many more people and it will cost less per person. A long boring one way trip for a colonist will be forgotten after living decades on Mars.

I would only use a fast transit for executives, politicians, rich turists, etc. who wouldn't be staying at their destination for the rest of their life.

prometheusunbound · 2003-07-04 15:06:47

I agree with you. The transaltanic trip would take a month in 1820 (start of the industrial revolution) and most of the people on ships would be staying in america (or europe) for at least 1-2 yrs or settle.

SpaceNut · 2005-06-03 09:41:53

We have been inter mixing the talk of cargo and transportation in many threads for a while for lack of any effort by Nasa seemingly willfully not seperating the two.
But will this concept work on the long haul to mars?

Aerojet lands NASA contract

Aerojet of Rancho Cordova has received a two-phase contract from NASA's Exploration Systems Mission Directorate to design, build, test and deliver a scaled-down version of an electric propulsion direct drive system that may someday be used by cargo transport vehicles on Mars and the moon.
Aerojet's direct drive system will deliver high-voltage power directly from space vehicle solar panels, to electric propulsion thrusters. This, Aerojet said, "will eliminate costly and heavy primary power converters and reduce solar panel size." Aerojet projects that its system will save 2,205 pounds of propellant during the vehicles' launches from Earth.

SpaceNut · 2005-06-03 11:42:29

CSI Applauds NASA's Agreement with GAO Report Reiterates readiness to deliver cargo to ISS in 2 years or less

Using off the shelf available systems..

Dook · 2005-06-06 18:54:24

You resurrect a two year old thread?

srmeaney · 2005-06-07 05:52:00

In space, a freighter could be 95% cargo. A space freighter is much different from an ocean going vessel that must be strong enough to resist the high seas, and the heavier the cargo the heavier the ship. You still need to fire retro rockets or aerobrake to get the cargo into orbit. Now, you could let the 5% that's freighter ship proper just fly on by while the cargo modules fire retros and then aerobrake. I guess that would amount to some efficiency. Solar sails would be great for cargos to and from Mars. A good article is in last month's Moon Miner's Manifesto about that. But why freighters at all? Doesn't Mars have everthing it needs? Or are you planning on selling light elements to lunar colonists?

Dont need to aerobrake in this situation. Cargo modules can do that as they penetrate atmosphere of Mars. All the modules need is a standard entry system to handle the Gforces and temperatures. The Megatonnes of food annualy that will need to be brought in will be most of it. The other is spare parts and unavailable resources such as nitrogen (unless we find that hidden subterranean sea of Ammonia, no one is gonna be able to gas up on Nitrous Oxide at giggle and squeek parties).

srmeaney · 2005-06-07 05:53:04

In space, a freighter could be 95% cargo. A space freighter is much different from an ocean going vessel that must be strong enough to resist the high seas, and the heavier the cargo the heavier the ship. You still need to fire retro rockets or aerobrake to get the cargo into orbit. Now, you could let the 5% that's freighter ship proper just fly on by while the cargo modules fire retros and then aerobrake. I guess that would amount to some efficiency. Solar sails would be great for cargos to and from Mars. A good article is in last month's Moon Miner's Manifesto about that. But why freighters at all? Doesn't Mars have everthing it needs? Or are you planning on selling light elements to lunar colonists?

Dont need to aerobrake in this situation. Cargo modules can do that as they penetrate atmosphere of Mars. All the modules need is a standard entry system to handle the Gforces and temperatures. The Megatonnes of food annualy that will need to be brought in will be most of it. The other is spare parts and unavailable resources such as nitrogen (unless we find that hidden subterranean sea of Ammonia, no one is gonna be able to gas up at giggle and squeek parties at your nearest spaceport fleshpit).

Fledi · 2005-06-07 10:38:33

There are really lots of different ways to get the cargo down to the ground. Either you send them in capsules with interplanetary maneuvering capabilities, or the mentioned interplanetary freighter with landing capsules, or even just containers coupled with a reusable martian shuttle, that would be little more than a big heat shield with landing rockets for transferring them from the freighter to the surface.
Will be interesting to find out which concept will prove to be the most efficient.

For the nitrogen, there is some in the Martian atmposphere that should be enough for the beginning, given it is recycled with high efficiency, but we will need much more if we choose to go for terraforming.

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