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The Rocketry Implications Of Portal Assisted Rocketry


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The premise for discussion involves portal gates that have a range of 7 lightyears. Spaceships using them use rocketry to reach orbit and are usually SSTO types because they have access to more propellant than their ships actually weigh via the portal gates carried on board.

Portal radius: Portal ship carried circular gates have a portal radius of 3 meters usually. Which is large enough to push an oblong propellant tank through.

Warping is used to reach other star systems in a reasonable amount of time.

Because of the 7 LY portal gate limit, spaceships carrying them will deposit spare gates every 7 LY of travel and use them as links with other gates every 7 LY.


The Main Question:

Just because spaceships can now  accelerate indefinitely in the home system won't mean they will. And I mean purely from an economic standpoint. Why?

Because the dirty litle secret of efficient high thrust rockets thrusting in space is that it is resourcefully wasteful.

What I mean is, for every 20 tons of LH you burn for a spaceship accelerating around the solar system, that's 20 tons of hydrogen from Earth you ARE NOT getting back (as it is likely exhaust at escape velocity anyway).

Possible solutions: Off world propellant refineries. Likely from icy moons no one is using. Why use Earth hydrogen when you can mine Europa and portal it off to fuel your growing portal equipped space fleet? Just drop a few portals off on a moon with equipment and workers, let them at it, and send them back to waiting ships at regular intervals.

Unexpected solutions: Artificial gravity is no longer a need, since crew can effectively hop from ship to ship through linked portals within the 7 LY range all the way back to the homeworld. Barring that they could also hop between portal satelites in deep space, but they need space suits for that to reach the next gate. You could go to a world 44 LY away and be back home for dinner if you wanted LOL. Assuming all the portal satelites were already laid in advance.

Any place actually interesting will already have linked portal satelites if it was previously explored, likely in an orbit high enough that it can be maintained without having a need for any boosting to counter atmospheric friction.

Additional questions: In such a setting will there still be a need for AM rockets? Or will NTR rockets rule just fine? Which engines will become obsolete? My guess? Solid propellant rockets, also kind of ion rockets.

What do you think? And bear with me, I already recognize that mixing tech levels may seem absurd...however it also uses things we ACTUALLY can grasp which puts at least SOME limits on activity that are based on known physics and not mere plot devices. That is why.

Edited by Spacescifi
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I think NTR, or potentially even plain old hydrolox will do just fine in this kind of setting.  If we have warp to handle exploratory travel to other star systems and build out that portal network, and the portals themselves to handle most other long distance space travel, then arguably we just need actual rocket engines for short-distance shuttling between portals. At which point, safe and cheap are probably our watchwords rather than high-powered and efficient. If we can get away with not using antimatter with its attendant storage problems, or nuclear anything with its attendant radiation hazards, then why wouldn't we?

And actually, this kind of tech level mixing works quite well to my mind. Whilst we're capable (in-setting) of producing and controlling vast amounts of energy for FTL travel and the portals, the reactors needed to generate that much energy are big and complicated and therefore either need a fixed installation to hold them (portal stations) or are relatively rare (FTL exploration ships. Either way, they don't lend themselves well to standard spacecraft, which are therefore made at the lowest possible tech level for cost, safety and robustness reasons. The 'if it aint broke, don't fix it' mentality if you like.

Going one step further (and taking a literal leaf out of Peter F Hamilton's books), do we need actual spacecraft at all, except possibly for portal building? Is there any reason why a portal needs to be built in space, or could we just put them planetside and literally drive from planet to planet at our leisure?

Oh - and a quick dig around on Google finds an estimated mass for Earth's oceans as 1.35 x1018 tons of water. Hydrogen makes up 11% of that by mass, so approximately 1.35x1017 tons of hydrogen. So yeah, chemical propulsion is kind of wasteful for the reasons you mention but on the other hand, we have an awful lot of mass to waste, particularly once we take off-world sources into account. :) 

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12 minutes ago, KSK said:

I think NTR, or potentially even plain old hydrolox will do just fine in this kind of setting.  If we have warp to handle exploratory travel to other star systems and build out that portal network, and the portals themselves to handle most other long distance space travel, then arguably we just need actual rocket engines for short-distance shuttling between portals. At which point, safe and cheap are probably our watchwords rather than high-powered and efficient. If we can get away with not using antimatter with its attendant storage problems, or nuclear anything with its attendant radiation hazards, then why wouldn't we?

And actually, this kind of tech level mixing works quite well to my mind. Whilst we're capable (in-setting) of producing and controlling vast amounts of energy for FTL travel and the portals, the reactors needed to generate that much energy are big and complicated and therefore either need a fixed installation to hold them (portal stations) or are relatively rare (FTL exploration ships. Either way, they don't lend themselves well to standard spacecraft, which are therefore made at the lowest possible tech level for cost, safety and robustness reasons. The 'if it aint broke, don't fix it' mentality if you like.

Going one step further (and taking a literal leaf out of Peter F Hamilton's books), do we need actual spacecraft at all, except possibly for portal building? Is there any reason why a portal needs to be built in space, or could we just put them planetside and literally drive from planet to planet at our leisure?

Oh - and a quick dig around on Google finds an estimated mass for Earth's oceans as 1.35 x1018 tons of water. Hydrogen makes up 11% of that by mass, so approximately 1.35x1017 tons of hydrogen. So yeah, chemical propulsion is kind of wasteful for the reasons you mention but on the other hand, we have an awful lot of mass to waste, particularly once we take off-world sources into account. :) 

 

Good points...I unknowingly broke the setting without even trying LOL.

You are right though. If portals are this good, then spaceships become mere portal gate shippers.

Since lets be honest...what's easier? Warping and adjusting speed and trajectory, surviving reentry, and doing a powered thrust landing...or just walking through a portal?

I forgot that humans will always take the path of least resistance unless they have a strong reason not to.

 

So now the only way to make spaceships still relavent would be to change the setting so much that spaceships ARE needed.

How? Portal gates still have a 7 LY range but only work in outer space vacuum...and I mean literally outside a spacecraft.

How does this change the setting? Now you NEED a spaceship to warp and lay portal gates. It also makes refueling propellant an EVA affair everytime you do, so max efficiency designed NTR LH will grant longer burns for that. Otherwise crew would be doing EVA every 5 min LOL using hydrolox.

Also spaceships use inertial guidance computer data to lay in a course for previously laid portal gates LY away.

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1 hour ago, Spacescifi said:

 

Good points...I unknowingly broke the setting without even trying LOL.

You are right though. If portals are this good, then spaceships become mere portal gate shippers.

Since lets be honest...what's easier? Warping and adjusting speed and trajectory, surviving reentry, and doing a powered thrust landing...or just walking through a portal?

I forgot that humans will always take the path of least resistance unless they have a strong reason not to.

 

So now the only way to make spaceships still relavent would be to change the setting so much that spaceships ARE needed.

How? Portal gates still have a 7 LY range but only work in outer space vacuum...and I mean literally outside a spacecraft.

How does this change the setting? Now you NEED a spaceship to warp and lay portal gates. It also makes refueling propellant an EVA affair everytime you do, so max efficiency designed NTR LH will grant longer burns for that. Otherwise crew would be doing EVA every 5 min LOL using hydrolox.

Also spaceships use inertial guidance computer data to lay in a course for previously laid portal gates LY away.

Ever played Mass Effect?

You're basically describing a nerfed Mass Relay for all intents and purposes, sure the mechanics are different (Relays make a "Corridor of massless space" which never made sense to me, since the ship still has inertial mass and thus wouldn't benefit. But i guess that's why they use their own ME effect devices to null out their mass, then again what's the relay for at that point....anyway this shouldn't be a spoiler filled breakdown of plot holes in ME's fictional tech).

But the gist is that for a ship to use a Relay to get to a planet, it still needs to at least be capable of interplanetary flight (Well above, Earth's relay was out at Charon). And it needs to have it's own propulsion, as the relay itself provides no motive force. It just minimizes the amount of energy needed to get from one destination to another. And the Relay can only go from one destination to another (In the case of "Primary" relays) but these can connect longer distances, while "Minor" relays can connect several hundred destinations. And computers are used to plot the course, because significant amounts of drift from the intended destination on the order of multiples of thousands of LY can be encountered even with the best efforts, so the ship also needs to be able to travel back to it's destination if needed. And the calculations need to account for the drift,  making sure the ship won't just smack into a planet or other obstacle.

And ofc these things aren't built by their discoverers, they're remnants of some long, long lost civilization. So they can't just make them, they use the ones they find. Oh and are paranoid AF about "Activating" dormant ones they haven't mapped the opposite "Pair" to, another good reason for having standard and FTL capable ships.

Really, if you want a fantastic example of how to merge "Conventional" and science fantasy elements/propulsion then I'd highly recommend at least looking into the first and second games.  Warning though, there's plenty of technobabble. Don't expect hard sci-fi from it.

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Also, there will be remote places for which having a portal might not be worth it (how much does those costs ?) Or in too much political tension that having one there might get people angry (and then, you have a fleet of angry people through your portal right on top of your home sector, sure you can do the same but it's weird, right ?). So there will be place for which you'll need a spaceship.

And portal builder ships. Like in The Long Way to a Small, Angry Planet. You need actual ship to send the portal building stuff at the newest portal destination. And it's going to take time to get there.

Basically, exploration (and war I guess) requires spaceships, even with portals.

For everything else ? Freight carriers and spaceliner, slow, reliable, mass produced, owned by cartels of companies to carry stuff through the portals and from the portals to the ground.

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If atmosphere does not spill out of a space suit during transit, and a fuel tank does not spill during transit, then why not just run a pipe through the portal?

Just pipe the hydrolox straight into the engine with powerful earth-mounted electrical pumps, no need for anything but a combustion chamber and engine bell.

Even just high-pressure steam would work fine, you would not even need actual combustion on your 'rockets'

If you don't want the pumps on earth, you need to switch to a 'transporter pad' type of arrangement, where you have distinct 'beaming' events.

(or go with the 'existing network of precursor gates' as suggested above.  'Magic' technology that is not properly understood is often a good reason why the technology has not been optimized for human use)

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42 minutes ago, Terwin said:

If atmosphere does not spill out of a space suit during transit, and a fuel tank does not spill during transit, then why not just run a pipe through the portal?

Just pipe the hydrolox straight into the engine with powerful earth-mounted electrical pumps, no need for anything but a combustion chamber and engine bell.

Even just high-pressure steam would work fine, you would not even need actual combustion on your 'rockets'

If you don't want the pumps on earth, you need to switch to a 'transporter pad' type of arrangement, where you have distinct 'beaming' events.

(or go with the 'existing network of precursor gates' as suggested above.  'Magic' technology that is not properly understood is often a good reason why the technology has not been optimized for human use)

 

Well...that I already knew. Thing is...it is still good to have a reserve tank for when one is out of portal range. Or if the portals only work in vaccuum, then that means Earth stations supplying propellant would be impossible (since no vacuum on Earth is quite as vaccuous as space vaccuum).

That means that moons without atmosphere would be prime real estate, and the best Earth could ever do is boost giant propellant tanks to orbit, and portal network them to moons that are being mined for ice for propellant...in order to refill their tanks regularly.

 

Wow...who knew ice would be so valuable? Without it, you can kiss your portal linked spacefleet goodbye.

I can even see scifi wars being fought over ice resources in systems...probably by imperialists who host vast fleets or even by trade empires which do the same but for reasons of profit rather than conquest.

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46 minutes ago, kerbiloid said:

If teleportally connect a moon without atmosphere to an atmosphere, it becomes a moon with atmosphere.

 

A through vacuum only portal.

Atmosphere won't apply.

Which makes refueling a tank affair through a portal.

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7 hours ago, Spacescifi said:

A through vacuum only portal.

Atmosphere won't apply.

Which makes refueling a tank affair through a portal.

If a full tank can pass through a vacuum portal, then a pipe passing through vacuum can also pass through a vacuum portal.

Even if our current industrial vacuums are not up to snuff, I expect the cost incentives would ensure a solution is quickly found to allow a portal to be created in a terrestrial vacuum chamber which can have a pipe run through the portal.

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14 hours ago, Terwin said:

If a full tank can pass through a vacuum portal, then a pipe passing through vacuum can also pass through a vacuum portal.

Even if our current industrial vacuums are not up to snuff, I expect the cost incentives would ensure a solution is quickly found to allow a portal to be created in a terrestrial vacuum chamber which can have a pipe run through the portal.

 

True...yet I meant that the portal gate must LITERALLY be surounded by the vacuum of open outer space.

Making an artficial one deeply within Earth and surrounded by Earth's deep atmosphere would not work.

Nonetheless....it's a throwaway concept I won't use for MC and main plot...mainly because I am not doing a space program story.

 

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Ian M Bank's Algebraist has portals that only work in flat areas of spacetime so any nearby mass, e.g. a planet causes the portal to explode. That leads to ships being used to get around inside a system and get to and from the portals which are in distant orbits. It isn't very compatible with portal based fuel transfer though.

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5 hours ago, tomf said:

Ian M Bank's Algebraist has portals that only work in flat areas of spacetime so any nearby mass, e.g. a planet causes the portal to explode. That leads to ships being used to get around inside a system and get to and from the portals which are in distant orbits. It isn't very compatible with portal based fuel transfer though.

 

Which means you need 'slow spaceboats' KSP style to reach them. Anything else is not practical.

I take issue when scifi uses space program era tech be the basis for spaceships that can do wayyy more than space programs can really do.

For example, rogue traders in space is totally not practical with fledgling space programs.

Such engines do not allow for unplanned deviations off couse either.

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12 hours ago, kerbiloid said:

We have gas giants.

True - but we know of no moon with enough gravity to become a gas giant, even if we use a portal to connect it to an atmosphere.  Absent sufficient gravity (and perhaps a magnetosphere) the portalled air will be stripped by the solar wind in time 

 

Nicht wahr? 

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