Paying For Propellant By The Gallon?

[Spacescifi]

Here Is The Scenario: SSTO's are common because everyone of them is networked via a portal network that links them to propellant stations on industrialized worlds.

Here is the catch: Portals tend to pulverize and or liquify solids that pass through. Not EVER used for passengers. For example if you throw an ice cube into a portal, it will become liquid on the other side. If you throw a rock or a piece of wood through it will blast into a cloud of debris. Liquid propellant is not effected and therefore is pumped through by shooting it across portals into a ready pipe on the other side.

Main Question: Say you want to be able to burn propellant for an hour at 1g in interplanetary space? Obviously heavier ships get billed more heavily.

What kind of price would a propellant station charge?

Is 1k (thousand dollars/credits) per hour of 1g sound reasonable?

Incidentally if you do something crazy they can also refuse to feed you any more propellant. Leaving you stuck with classic NASA scenarios and the tyranny of the rocket equation.

Question 2: Would not some propellants be cheaper or pricier? Obviously doing higher accelerations for hours will be plenty costly too.

What would be the dirt cheap propellant? Saltwater? Not even processed...but does require onboard ship machines to separate the LOX and LH out. Or a nuclear reactor to just use it straight as propellant.

Mid-price propellant?

Expensive propellant?

Probably the toxic high thrust stuff like mercu-LOX (liquid mercury and liquid oxygen). Or just burning liquid fluorine with a nuclear reactor.

Why is RP-1 propellant considered to be so good?

Hilarious question, but what would RP-101 look like or be?

 

Thanks.

Edited April 17, 2021 by Spacescifi

[kerbiloid]

Hang it under a balloon and let it float on Saturn.

[Shpaget]

5 hours ago, Spacescifi said:

For example if you throw an ice cube into a portal, it will become liquid on the other side. If you throw a rock or a piece of wood through it will blast into a cloud of debris.

Why it doesn't pulverize ice? Or if it melts ice, why it doesn't melt rock?

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Liquid propellant is not effected and therefore is pumped through by shooting it across portals into a ready pipe on the other side.

How does the ship request fuel?

Quote

What kind of price would a propellant station charge?

Is 1k (thousand dollars/credits) per hour of 1g sound reasonable?

How much yoghurt can you buy with 1k credits?

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Question 2: Would not some propellants be cheaper or pricier? Obviously doing higher accelerations for hours will be plenty costly too.

Sure. Why would you have the same price for every propellant, unless the cost of the propellant itself is insignificant compared to the cost of portal services.

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Why is RP-1 propellant considered to be so good?

It's cheap and burns well, doesn't explode if you look at it wrong, is liquid at room temperature, is much denser than (even liquid) hydrogen, and doesn't immediately give you cancer if you spill some of it.

Quote

Hilarious question, but what would RP-101 look like or be?

Do you think it has a "1" in its name because it's the crappiest of all the RPs?

Edited April 17, 2021 by Shpaget

[KSK]

Impossible to say what a reasonable price for propellant would be.  Taking the obvious point first (as alluded to by @Shpaget) - what is $1000 or 1000 credits worth in any of today's currencies? 

I'm not an economist, so at the risk of looking dumb, I would think that the cost of propellant will reflect the supply of propellant and the demand for propellant. Both of which can depend on many factors. Supply, for example will be influenced by the cost of the portal system, the cost of whatever mining and refining gear used to extract the propellant and, possibly the physical quantities of propellant available for extraction.

Then you get into the whole political situation. Is there a free market in propellant portals, with multiple companies in competition? That might lower prices but,  at first sight, it seems unlikely, given that the portal  system would appear to be a significant strategic asset, which suggests government oversight and maybe outright control. How benign is that government? How many governments are there? Each government will probably want its own portal/propellant network or at least to have guaranteed access to one, in much the same way that present day governments want access to a satellite navigation system.

On a somewhat related note, what sort of flow rates can you get through a portal and is there any temperature limit for matter transmitted through a portal? Because I was wondering if it would be possible to effectively have remote spacecraft engines. Build the engine next to the propellant depot and then literally fire it into one end of the portal. Hot gases get transmitted across to the spacecraft and out through the other end of the portal. Maybe have the portal exit in the nozzle throat of the spacecraft engine and then have the nozzle function as normal to direct and accelerate the outgoing gas.

Couple of interesting follow up thoughts. Depending on how the portal network is set up (can it be reconfigured on the fly?) it might be possible to have multiple spacecraft 'timesharing' on the same engine.

Also, this might solve a problem that you've previously brought up here - how to have personal spaceships when each spaceship can be a dangerous weapon. Remote engines effectively cede control of your ship to the portal network operator, so you're not going anywhere significant in your personal ship unless you have authorization.

 

 

[magnemoe]

Well the cheapest would be methane and oxygen, might even air. 
Or as KSK proposed use an remote engine.  This offers some interesting options like simply putting portals in the depths of the sea.

However to make this a bit more realistic: the sender portal will require the power like the difference in kinetic energy between the rocket and the sender station. 
Its not an totally free lunch you just don't need the fuel tanks and to lift them with rocket engines. 
Therefore you will want high performance fuel, one problem with pre burning the fuel is that you can not use this to cool the engine on the rocket. 
I probably use methane and oxygen to get to orbit and hydrogen and oxygen in space. 

[kerbiloid]

Skype, tram, maglev. No need in chemical fuel outside the powerplants.

[Gargamel]

6 hours ago, Spacescifi said:

Why is RP-1 propellant considered to be so good?

 

1 hour ago, Shpaget said:

It's cheap and burns well, doesn't explode if you look at it wrong, is liquid at room temperature, is much denser than (even liquid) hydrogen, and doesn't immediately give you cancer if you spill some of it.

Once of the reasons is that it's easy to obtain (refinery).   It's petroleum based though, and that's a finite resource.  It requires a planet that has had a substantial amount of biomass to decay into crude oil over the eons.  Not many of those in our solar system, and if you're setting this in the future, then the availability of crude oil to make such stuff is probably going to be very very limited.   RP-1, as we know it,  should then be very expensive to obtain. 

[Shpaget]

9 minutes ago, magnemoe said:

However to make this a bit more realistic: the sender portal will require the power like the difference in kinetic energy between the rocket and the sender station. 

An potential energy as well, otherwise you could just teleport water up a gravity well and run a turbine to generate power. Instant perpetuum mobile, and we can't have that.

Fixing that will result in optimal places to establish fuel depots to be in as high orbits around the Sun as possible. Using the fuel in the inner system will come with some extra "free" energy, but going outside the system will require additional input. If you go interstellar, you will need to account for galactic gravitational potential energy as well.

[Gargamel]

1 minute ago, Shpaget said:

An potential energy as well, otherwise you could just teleport water up a gravity well and run a turbine to generate power. Instant perpetuum mobile, and we can't have that.

As Glados put it, speedy thing in, speedy thing out.    The fine print is that speedy must equal speedy.    Can't have added energy can we?

[kerbiloid]

If put the portal close to an event horizon, we can be mining strange things.

[KSK]

2 hours ago, Gargamel said:

Once of the reasons is that it's easy to obtain (refinery).   It's petroleum based though, and that's a finite resource.  It requires a planet that has had a substantial amount of biomass to decay into crude oil over the eons.  Not many of those in our solar system, and if you're setting this in the future, then the availability of crude oil to make such stuff is probably going to be very very limited.   RP-1, as we know it,  should then be very expensive to obtain. 

Couldn't you synthesize it, or something close to it? Water plus a carbon source would give you the raw materials for Fischer-Tropsch synthesis and neither of those are terribly hard to find in space. More speculatively, it might be possible to distill something out of tholins, which are rarer but not super rare either. Titan, I'm looking at you, or (according to a podcast I just listened to), Kuiper belt objects might be a more reliable source.

Admittedly, Fischer-Tropsch or rendering down tholins seems likely to be more expensive than methane for methalox engines or, if nuclear-thermal is an option, just plain old water, hydrogen (as per @kerbiloid's suggestion to go to Saturn), ammonia or pretty much anything else that you can scrape up off the ground and which doesn't gunk up the motor too badly, would be fine. 

With what amounts to an infinite fuel hack available, I'm not so sure that raw engine performance is a priority compared to keeping it simple, rugged and cheap.

[Gargamel]

2 minutes ago, KSK said:

Couldn't you synthesize it, or something close to it?

You could, but I said "as we know it".   It wouldn't be the same as RP-1, it'd be RP-1a or some such. 

[YNM]

Price is determined by how much money went into procuring/producing and distributing said product. A while ago gas price on different islands in this country varies by like 10% on a 'further' island.

So it really depends on your scenario.

Say that fuel is automagically transported everywhere. Then you don't include transportation price in your system at all, it only goes to maintaining the facility itself, as well as the fuel production itself (both consumables and non-consumables).

Say if fuel has to be transported with a cost. Then most likely the further out you are from their source the more expensive they are.

But it doesn't stop only with distance... There's time as well, in times of scarcity it'll be more expensive, in times of plenty (or low demand/desirability) then it'll be cheap.

 

As for expensive vs. cheap fuel... Well you have three aspect :

1. What material is in it

2. How was it produced

3. How desirable is it

The first two is obvious - the price for oil, peat, coal and wood is different because they're different things and they're produced differently - but the last one isn't that obvious. Take for example octane and cetane rating. It doesn't have anything to do with the materials inside of it, but almost always you're going to see that fuels with higher octane rating is sold more expensively. Does it actually take more money to produce ? Not necessarily. Is it actually better to use ? Not necessarily.

I will say that purity is still in point 1 however, so paying for 70% ethanol and 100% ethanol is going to be different since you're buying different things inside.

Edited April 17, 2021 by YNM

[Codraroll]

Pair up two portals. Mount one at the back of your ship (which preferably should be in orbit already and, this is important, quite a bit distant from any local police force). 

Then throw the other portal into the sea.

[YNM]

11 minutes ago, Codraroll said:

Pair up two portals. Mount one at the back of your ship ... throw the other portal into the sea.

The Dutch plan for world domination.

[kerbiloid]

Put one above a pulsar and get a shower of high energies for free.

[Spacescifi]

7 hours ago, Gargamel said:

As Glados put it, speedy thing in, speedy thing out.    The fine print is that speedy must equal speedy.    Can't have added energy can we?

 

Are you saying that if I throw am item to a portal in LEO, it WON'T pass through UNLESS it is going at orbital velocity?

 

If that is the case propellant depots will be massive to accelerate stuff.

Make a water cannon that sprays at orbital velocity much?

 

Neither do I LOL.

 

High tech requires high tech!

[Gargamel]

8 minutes ago, Spacescifi said:

Are you saying that if I throw am item to a portal in LEO, it WON'T pass through UNLESS it is going at orbital velocity?

No... I'm saying if you pass an ice cube through a portal, and it comes out as water.. You've added energy to the ice.   Where did this energy come from?    It came from the portal, either one.  How is the portal generating this energy?

Why doesn't liquid get this energy increase?

Edited April 17, 2021 by Gargamel

[Spacescifi]

7 hours ago, magnemoe said:

Well the cheapest would be methane and oxygen, might even air. 
Or as KSK proposed use an remote engine.  This offers some interesting options like simply putting portals in the depths of the sea.

However to make this a bit more realistic: the sender portal will require the power like the difference in kinetic energy between the rocket and the sender station. 
Its not an totally free lunch you just don't need the fuel tanks and to lift them with rocket engines. 
Therefore you will want high performance fuel, one problem with pre burning the fuel is that you can not use this to cool the engine on the rocket. 
I probably use methane and oxygen to get to orbit and hydrogen and oxygen in space. 

 

Oh I get it.

 

Just using a nozzle is more efficient for a portal system because shooting propellant orbital velocities to match portal speed is harder.

You can still cool ship with onboard LH tanks and use radiators to slowly cool them down.

It also means you probably cannot thrust indefinitely...even with portals.

 

Unless you have one where the speed between portals is a lot closer and you are spraying propellant between portals in directly to your ship tanks.

 

2 minutes ago, Gargamel said:

No... I'm saying if you pass an ice cube through a portal, and it comes out as water.. You've added energy to the ice.   Where did this energy come from?    It came from the portal, either one.  How is the portal generating this energy?

Why doesn't liquid get this energy increase?

Real reason? It's cool for how I can use it for eliminating certain...stuff. Cool effects

Heh heh....arbitrary plot man...don't think about it...don't think about it.

I actually prefer clasdic portals where speedy thing goesin speedy thing goes out and that speed is ADDED on top of exit portal speed as opposed to having a speed budget have to reach before you can even go through an exit portal.

[Spacescifi]

10 minutes ago, Spacescifi said:

 

Oh I get it.

 

Just using a nozzle is more efficient for a portal system because shooting propellant orbital velocities to match portal speed is harder.

You can still cool ship with onboard LH tanks and use radiators to slowly cool them down.

It also means you probably cannot thrust indefinitely...even with portals.

 

Unless you have one where the speed between portals is a lot closer and you are spraying propellant between portals in directly to your ship tanks.

 

Real reason? It's cool for how I can use it for eliminating certain...stuff. Cool effects

Heh heh....arbitrary plot man...don't think about it...don't think about it.

I actually prefer clasdic portals where speedy thing goesin speedy thing goes out and that speed is ADDED on top of exit portal speed as opposed to having a speed budget have to reach before you can even go through an exit portal.

 

In that case portals would actually slow stuff down.

 

Anything in orbit cannot send anything to. Earth without slowing it down Doubt they can do that on an orbitng ship already going that fast.

 

So you really cannot afford to think about the why too much to enjoy the story.

[wumpus]

On 4/17/2021 at 3:35 AM, Shpaget said:

It's cheap and burns well, doesn't explode if you look at it wrong, is liquid at room temperature, is much denser than (even liquid) hydrogen, and doesn't immediately give you cancer if you spill some of it.

I'm wondering why kerosene was preferred over methane at the start of the space race.  I'd guess that the pressure vessels were too heavy, and that cooling two tanks wasn't worth it (presumably to lower the pressure).  You have to refine kerosene into RP-1, and the volume is so low that I'm sure it is a relatively expensive thing to do.  After that, existing designs made RP-1 the preferred fuel until spacex decided that even RP-1 had too much coking, and that hydrolox wasn't an option.

Back to the original question, propellant costs will presumably vary locally depending on how hard it is to maintain supply. And expect to buy it by the kg, as the volume can vary over temperature (spacex makes a big deal out of this).

A fairly busy gas station can require multiple trucks filling it up daily (this makes hydrogen cars sound even more like a pipe dream than without said tidbit), and you'd have to ask yourself how are the propellents brought to the depot.  Ion or other electric thrusters (using either argon or hydrogen) should be the cheapest means to high delta-v depots, while other places might have "moon rock" based propellents (I've heard you can make stuff with a relatively bad Isp, but the location might make it worth it), Mars made propellants (metholox), and elsewhere.  The classic "skim a gas giant" trope is likely  way too far in a gravity well to be useful, but some of these others might work.

So the real question comes down to competition and price fixing.  Assuming one "celestial body" = "one government" (a classic SF trope), expect that the price of Earth-based fuels (moved by ions or similar), Mars based fuels, and Lunar based fuels are all roughly based on what a another planet (or moon) could supply to said location.  The local product either slightly undercuts this, or perhaps happily goes over it assuming a price war would be too costly to maintain .

[Spacescifi]

 

Since reaching altitude anf velocity can take all of eight minutes IRL, I think 100 credits a minute is a reasonable price.

 

Keeps folks, unless they are rich, from burning around at 1g all the time. Also allows for kilometer long tether pod rotation for graviyty to be cheap...or what average space folk do. Burn and coast.

[K^2]

Even if you can't transport people through it, the moment you have ability to create portal networks, the concept of fuel for propulsion becomes meaningless. Drop a portal at the bottom of an ocean and just pump sea water through it at adequate pressure. Your SSTO's propulsion system can be literally a hose with a nozzle. I mean, we literally have jetpacks/hoverboards based on that principle that run off a jetski. The only downside is the really long hose you need, which you entirely circumvent with a portal. And this is without getting high-tech about it, which is a pretty big rabbit hole.

Seriously, ability to transport mass across vast distances without it having to travel anywhere in between is the end game. You figure out that, and the rest is just an engineering problem.

[Jacke]

Of course, there's still Emmy Noether's Theorem, so the way space looks and acts, that means there's conversation laws.  And a glibly designed Portal system ain't going to work.

https://en.wikipedia.org/wiki/Noether's_theorem

(Fun fact: the whole universe can break those conversation laws because there's no way when considering the whole universe to do the things that lead to them.  'Course, there's no way to leverage that.)

Larry Niven for his teleportation system in his SF stories imagined a huge compensation mass floating in the Great Lakes to prevent breaking the conservation laws.  Something similar would have to be done.

[Codraroll]

10 hours ago, Spacescifi said:

Since reaching altitude anf velocity can take all of eight minutes IRL, I think 100 credits a minute is a reasonable price.

That depends entirely on the value of the credit.