Terra, Luna, and Ceres - Triangle Trade

Terraformer · 2020-04-07 11:46:18

tahanson43206 wrote:

Is there a natural trading relationship between Mars and Ceres?

Nothing immediately springs to mind. Orbital mechanics permitting, there is a far more obvious trading relationship between Ceres and Luna, since they both have in abundance what the other lacks, and the prospect of putting cargo into orbit very cheaply (tethers for Ceres, mass drivers and possibly space elevators for Luna). Ceres has a *lot* of water, which is lacking on Luna, as well as (probably) a lot of carbon and possibly some nitrogen, but its rocky material is mostly clay. Luna, on the other hand, has plenty of basalt, and the energy available to supply aluminium, and maybe free iron, but aside from the cold traps at the poles it doesn't have much in the way of volatiles.

Together, though, they complement what is lacking in each, and with Terra would form a triangle trade. Volatiles (mostly, water) from Ceres; construction material from Luna, for ships and habitats; and from Terra, humans and high tech goods. The vast bulk of goods by mass would be coming from the first two, so even if we don't get costs <<<$100/kg from Terra we will be able to afford big projects in space.

Which means I need to get down to work. If I can monopolise the equator of Ceres through paraterraforming, I can control all elevators, and so undercut anyone else who tries to also operate there. This will give me time to complete the Great Work of paraterraforming the entire planet...

SpaceNut · 2020-04-07 11:59:19

There has been a few trade studies for triad locations (MIT was one) of like you indicated are based on what you have and have not for economics of building and sustaining. Its not a cash system but equitable trade as rockets and fuel are at stake for the cargo and they are setup for a oneway commerce as the container to hold water is not the same that you would use to move gasses or other materials.

louis · 2020-04-07 12:27:57

I can't think of one apart from tourism. Once Mars is settled and the population is significant then I expect some of them will want to explore Ceres. Why not? They would be adventure holidays.

Anyone know how long the journey from Mars to Ceres might take?

tahanson43206 · 2020-04-07 12:55:16

For Terraformer re topic ... I think ** this ** one should have legs! Congratulations on your insight, and best wishes for the topic.

For SpaceNut ... Thanks for the reminder of the MIT study on triangle trading relationships. I thought immediately of the famous one from the colonial period, but look forward to seeing the historical record for others.

For SpaceNut ... Sometimes you say things that leave me baffled ... what did you mean by:

as the container to hold water is not the same that you would use to move gasses or other materials.

On Earth, the ubiquitous shipping container is used to move anything and everything. In space that concept will repeat, since even though it took humans centuries of ocean shipping before anyone thought of the "universal" container, surely humans transitioning to space business will employ the concept from the beginning. Recently (I'm pretty sure right here is this forum) someone suggested Elon's concept of a one-size-fits-all rocket vehicle will perform that same function.

For Louis ... It remains to be seen, but it might prove competitive to ship water from Ceres to Mars (Phobos) than to ship water from Mars to Phobos.

It might even be competitive to ship water from Ceres to Mars surface compared to mining it on Mars itself.

The capitalist system will insure that the most economical process will enjoy the greatest returns.

(th)

SpaceNut · 2020-04-07 14:34:12

The shipping container for cargo on earth is a connex box that holds that actual containers that hold the water and other things, sort of a box in a box where you must make the packaging of you item fit the connex box.
You are not filling the connex box with dirt or water without the internal packaging.

Terraformer · 2020-04-07 15:44:29

louis wrote:

I can't think of one apart from tourism.

I... just gave it. Ceres has lots of volatiles, and prospect of shipping them cheaply using tethers. Luna has very little volatiles, but it does have basalt and metals, which could be launched via railgun at low cost, as well as abundant solar power. Terra has, and will have, high shipping costs, but it has plenty of people and high tech goods which it will be difficult for Luna or Ceres to manufacture on their own for quite a while. Hence trade.

louis wrote:

Anyone know how long the journey from Mars to Ceres might take?

Depends on your ship. At their closest conjunction, Ceres and Mars are still thrice as distant as Terra and Mars. But if you have a fast ship, maybe using beamed power, you could still do it in a few weeks. With chemfuel, though... no, you're talking about quite a long distance to travel.

SpaceNut · 2020-04-07 16:17:42

To save on weight, a detour to the moon is the best route to Mars

For a piloted mission to Mars, fueling up on the moon could streamline cargo by 68 percent.

http://strategic.mit.edu/spacelogistics/

louis · 2020-04-07 19:59:03

I think you are confusing geology with economics. Lots of places have lots of things on our planet but people don't dig them up, harvest them or collect them with a view to transporting them somewhere else - because the economics don't make sense. Ceres may have volatiles but under any imaginable solar system economy, as you envisage, then travel from Earth to Moon would be relatively easy. Which begs the question why you would bring volatiles from Ceres to the Moon when you can bring them from Earth to the Moon - a mere 250,000 miles away.

Terraformer wrote:

louis wrote:
I can't think of one apart from tourism.
I... just gave it. Ceres has lots of volatiles, and prospect of shipping them cheaply using tethers. Luna has very little volatiles, but it does have basalt and metals, which could be launched via railgun at low cost, as well as abundant solar power. Terra has, and will have, high shipping costs, but it has plenty of people and high tech goods which it will be difficult for Luna or Ceres to manufacture on their own for quite a while. Hence trade.

louis wrote:
Anyone know how long the journey from Mars to Ceres might take?
Depends on your ship. At their closest conjunction, Ceres and Mars are still thrice as distant as Terra and Mars. But if you have a fast ship, maybe using beamed power, you could still do it in a few weeks. With chemfuel, though... no, you're talking about quite a long distance to travel.

Last edited by louis (2020-04-07 19:59:31)

Terraformer · 2020-04-08 02:34:59

louis,

Because launching them from Terra to Luna requires a stonking great big rocket ship and is very expensive, that's why. *You* are the one here confusing geography and economics.

What is cheaper, helicopter air freight from a few hundred miles away, or cargo ship sea freight from half the world away?

If Ceres can fling ice very cheaply back to Luna, then it doesn't matter if it takes a year to arrive, it can still out-compete importations of hydrogen from Terra. Even if launch costs are as low as $10/kg, launching 110,000 tonnes of hydrogen (to make 1,000,000 tonnes of water) would cost $1.1 B. If we want to do big projects in space, we need to be getting our volatiles from elsewhere, and Luna only has enough for getting started.

tahanson43206 · 2020-04-08 06:54:33

For Terraformer re #9

Your idea of building a space elevator for Ceres commerce seems worth developing further.

Depending upon your skill set, it would not be unreasonable to ask for help from someone who has specialized knowledge about design of such a system.

You can start by posting a message or two showing the physical parameters that must be included in your design.

No doubt you are aware that a counter weight is needed to sustain tension along the cable.

A moon around Ceres would be nice, but (I gather) there are none.

You could start your project by bringing a small asteroid into orbit around Ceres, and extend your cable from there.

Since there is a very small talent pool in the active membership of this forum, you could (presumably) write letters-to-the-editor enlisting folks to help you with the project from your local community. After all, they are all (or most are) at home, looking for something to do over the Internet.

(th)

Last edited by tahanson43206 (2020-04-08 06:55:00)

Terraformer · 2020-04-08 07:40:22

A large counterweight is only needed if the cable stops in synchronous orbit. A Cererean tether would extend past it, to enable cargo to be launched into interplanetary space using the rotational energy of Ceres. In any case, it would be trivial to bring up mass from Ceres itself to use as a counterweight.

With a circumference of 3000km, there is plenty of room on the equator for elevators.

tahanson43206 · 2020-04-08 07:57:11

For Terraformer re #11

The cable ** cannot ** stop in synchronous orbit!

If you pulled a cable to synchronous orbit, it would fall back down.

For those forum readers who may be interested in this discussion, there is a nicely written article on the subject:

https://en.wikipedia.org/wiki/Lunar_space_elevator

There are entire books available on the subject of space elevators.

(th)

Terraformer · 2020-04-08 08:45:21

If the counterweight is heavy enough, you pretty much can (okay, so it will be slightly further out than synchronous, but there isn't much in it). But if you extend a cable further out far enough, the tip will be moving faster than escape velocity, and you can drop payloads off into (or catch them from) interplanetary trajectories without any propellent.

If we can develop long distance microwave beaming, though, we could move stuff around anyway with high Isp, low thrust propulsion anyway, so it's less of a benefit. But we still need them to get off bodies - Cererean gravity is high enough that a ship with 0.1 m/s^2 acceleration, capable of adding 8.5 km/s per day (far higher thrust than anything built so far), would be unable to lift off. But it could be loaded up at an elevator station and sent on its way. I definitely think microwave beaming is a technology we need for serious colonisation.

SpaceNut · 2020-04-08 08:52:55

The counter weigh is use to counter the mass that ascends the cable to the launch location as we are using momemtum to make it not fall back down. The mass weigh of materials are low on cere's and a simple tower works as well.

A moon is possible if you can make it settle into a circle orbit that can be maintained from any pick of rocks in the belt.

An EML launcher seems very reasonable from a high place platform to control shipping of mass towards the moon.

tahanson43206 · 2020-04-08 09:07:26

For SpaceNut re #14

Thanks for your interesting contributions to Terraformer's vision for commerce from Ceres!

To clarify something, and build on your post .... the FIRST and ESSENTIAL role of the counterweight is to hold the cable against the gravity of the rotating body to which it is attached at the bottom. The entire mass of the cable will be constantly drawn toward the center of the body. The counter weight is placed far enough from the center of mass of the structure, and it has enough mass itself, to support the cable. A rule of thumb is to allocate as much cable to the counterweight as you allocate to the descending leg of the elevator, but (of course) that is adjustable depending upon numerous factors.

However, to the specific point you made ... the counterweight will be a repository of stored momentum. As you lift an object from the surface of whatever body you are working with, the mass of that object will have to be accelerated until it possesses the momentum needed to keep it in orbit at the synchronous location.

Where does that momentum come from?

The momentum comes (primarily) from the counterweight, which (of course) shifts West (anti-spinward) as the payload ascends the cable.

That momentum has to be made up.

At the moment, as Terraformer is developing his mental model of a space elevator at Ceres, he has NOT provided for how to replenish the momentum he had previously stored in the counterweight.

Without a means of recovering that momentum, the entire structure is at risk of falling down.

Fortunately, Terraformer has shown a willingness to learn. In a person of Terraformer's (presumed) advanced age, that is really saying something!

Accordingly, in the weeks ahead, as Terraformer confronts the physics of his concept, it is to be hoped he will share his unfolding understanding with the forum, and thus help those millions of (potential) readers who know nothing at all about the subject.

It is said that it takes 10 Earth years for someone to become an expert on a subject.

We can hope that Terraformer will resolutely set out to become an expert, and we should see the results as we go along here, if he remains willing to share his progress.

(th)

Last edited by tahanson43206 (2020-04-08 09:08:03)

SpaceNut · 2020-04-08 11:15:15

Space elevators is physics extreme and material science for sure with a dash optimism.

Lets continue the elevator physics in one those other topics.

Like how to use an Inflatable towers in Venus topic for cere's instead.
Inflatable space elevator gets a lift

Space Elevators and Pipelines

Space Elevators.....How Soon?

Space elevator - breaktroughs predicted

Space Elevator pilot program?

Space elevator in the media - dÃ©jÃ vu?

Terraformer · 2020-04-08 12:08:06

th,

I'm less than six Ceres years old. I wouldn't quite call that advanced...

I know about the angular momentum issue. Usually, the proposed solution is to use an ion drive to keep reboosting the counterweight, though trading mass down the gravity well also works.

It's a shame Hop doesn't post here any more. He's very big on tethers.

EDIT: Hop's blog results re. a Cererean tether.

Last edited by Terraformer (2020-04-08 12:10:13)

tahanson43206 · 2020-04-08 13:51:22

For Terraformer re #17

Glad to know you're just a youngster (On Ceres << grin >>)

Glad you know about angular momentum. Your earlier post content was what led me astray. Probably just limitations of text as a communications medium.

An ion drive is an interesting solution, which I had not heard offered before. Perhaps it has become more significant as a possible solution as more powerful ion drives have become feasible.

For someone who has time on their hands AND the math skills to bring to bear, please develop a post that shows how much thrust an ion engine would need to develop for how long, if it is going to compensate for the angular momentum that would be lost by a counterweight for a space elevator at Ceres.

For simplicity, please perform the calculation for a payload mass of one metric ton, delivered to the synchronous orbit way station. Again for simplicity, please assume NO mass for the lifting mechanism. Finally, since the time of travel is a factor, let that be 7 Earth days of 24 Earth hours.

SpaceNut, I'm looking for someone new, or someone who has not posted in a while, to take this on.

For Terraformer ... thank you for bringing the forum member name of Hop back into view, and specifically the blog to which you provided a link.

I was ** impressed ** by the quality of the blog series, and look forward to going back to study it more carefully.

Finally .... I've opened a new Physics topic. If you think that Hop's postings or blog are suitable for that new topic, please consider adding links there.

Had it not been for your bringing Hop's ID forward, I'd not have learned about his high quality work.

(th)

Terraformer · 2020-04-09 03:26:52

Actually, thinking about it more, we should be able to recover the angular momentum by releasing payloads at the tether tip, 2000km from the surface. The energy for launching the payloads will be taken from the rotation of Ceres itself, but with a fast (9 hour) rotation period and very large mass, that's not a problem.

Above the counterweight in equatorial orbit, the tether will be moving faster than orbital speed, so any payload on it would be pulled towards the end of the tether. This will have the effect of raising the counterweight. We could even use it to generate power to raise cargo from the surface, if it's long enough, allowing us to export water and carbon for free in energy terms (again, by stealing from the rotational energy of Ceres).

That said, it's still a multi-year flight time if we just use the speed available from tethers. Beamed microwave propulsion would get that down to months.

tahanson43206 · 2020-04-09 09:50:02

Edit #1 ... this post was offered in hopes Terraformer might clarify a point he had made in the previous post.

The clarification was made, so the request was removed.

(th)

Last edited by tahanson43206 (2020-04-09 15:25:22)

Terraformer · 2020-04-09 13:54:23

Ah, I see my error here. Moving a payload from the surface *to* the tether tip should be doable without the counterweight changing altitude - the force of the payload 'dropping' (as from it's perspective, the end is down) to the tip would counterbalance the force required to raise it to the counterweight in synchronous orbit. The same principle that enables a siphon to raise water against gravity.

The problem comes when the payload is released, since it's no longer a closed system. The loss of tension in the upper tether will cause the counterweight to drop again. This could be countered by either receiving an equal amount of mass going down the elevator, or more likely, by using some high efficiency means such as an ion engine to raise the altitude again.

Unless we can make a compressive structure, in which case we *could* export stuff for free using the rotational energy of the planet... steel has a compressive strength of 250 MPa (depending on the steel), and a density of 8 tonnes per cubic metre, so a non-tapering tower made out of solid steel could go up to 300m on Terra. On Ceres, only 12 km. Not good enough. On the other hand, we could use an inflatable tower...

But I digress. The important thing is that an elevator on Ceres is (if we're at the point of going there) practical and useful, and this is the economics subforum.

tahanson43206 · 2020-04-11 12:10:26

For Terraformer re topic ...

I'm hoping to encourage you to develop this topic. I agree that worrying about the details of a space elevator can be relegated to another topic, and we have done that. I'm hoping to find time to get back to the HOP references you provided, because the work done appears to be first rate and worth serious study.

However, the **purpose** of this topic (as I understand it) is to forecast and (perhaps) to influence early thinking about how a Solar system economy can be made to work to the benefit of not only the investor Job Creators, but the millions of Job Holders who are now and always will be dependent upon Job Creators.

By identifying promising trade opportunities as you have already started to do, you will be (hopefully) inspiring forum readers for years to come.

(th)

louis · 2020-04-11 13:49:42

Good attempt but in this case the mode of transport is the same for Earth-Moon and Ceres-Moon: big stonking rockets.

Just setting up a spaceport on the Moon with full rocket maintenance facilities is going to way more expensive than setting one up on Earth. You've still got to dig up your ice on Ceres, pack it and all the rest - using robots by the sound of what you are proposing.

Meanwhile on Earth thngs couldn't be easier if you were loading a rocket with water or ice.

I think it's much more likely that facilities on the Moon will just use very efficient water recycling. I don't see the Moon as a huge original water user. It's not going to be a big base for industry and manufacture. It's much more likely to be a tourist destination with 10s of thousands taking a holiday there every year, getting married there, honeymooning there, visiting the iconic Apollo landing sites, playing lunar golf and messing around in lunar rovers.

Terraformer wrote:

louis,
Because launching them from Terra to Luna requires a stonking great big rocket ship and is very expensive, that's why. *You* are the one here confusing geography and economics.
What is cheaper, helicopter air freight from a few hundred miles away, or cargo ship sea freight from half the world away?
If Ceres can fling ice very cheaply back to Luna, then it doesn't matter if it takes a year to arrive, it can still out-compete importations of hydrogen from Terra. Even if launch costs are as low as $10/kg, launching 110,000 tonnes of hydrogen (to make 1,000,000 tonnes of water) would cost $1.1 B. If we want to do big projects in space, we need to be getting our volatiles from elsewhere, and Luna only has enough for getting started.

Terraformer · 2020-04-11 14:05:44

louis,

Why would we use big stonking rockets, when we don't have to? Tethers, mass drivers, electric thrusters... in space, these are options, and superior ones to rockets in most cases.

Unless we're willing to use nuclear rockets, transport from the Terran surface is always going to be very expensive compared to transport in space itself. You can't just "load a rocket with water", and more than you can transport oil by air freight. An oil tanker takes far longer, but unlike trying to fly the oil, it's actually possible to make a profit on it.

tahanson43206 · 2020-04-11 16:29:09

For Terraformer re #24

This topic has a theme with historical parallels.

I am interested in seeing a development of your basic idea.

(th)

Last edited by tahanson43206 (2020-04-11 18:24:59)

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#1 2020-04-07 11:46:18

Terra, Luna, and Ceres - Triangle Trade

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#3 2020-04-07 12:27:57

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#6 2020-04-07 15:44:29

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#7 2020-04-07 16:17:42

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#8 2020-04-07 19:59:03

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#9 2020-04-08 02:34:59

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#10 2020-04-08 06:54:33

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#11 2020-04-08 07:40:22

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#12 2020-04-08 07:57:11

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#13 2020-04-08 08:45:21

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#14 2020-04-08 08:52:55

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#15 2020-04-08 09:07:26

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#16 2020-04-08 11:15:15

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#17 2020-04-08 12:08:06

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#18 2020-04-08 13:51:22

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#19 2020-04-09 03:26:52

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#20 2020-04-09 09:50:02

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#21 2020-04-09 13:54:23

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#22 2020-04-11 12:10:26

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#23 2020-04-11 13:49:42

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