[Spaceships] getting into orbit without superscience?

[Gnaskar]

Imagine a newly colonized world. They have orbital launch capability in the form of a pair of reusable two stage sea planes, maintained in a prefabricated hanger by the shores of the settlement. In orbit sits their old colony ship (without the propulsion bus, which was sold to another colony expedition). So it's basically empty storage, some stripped down habitation and a hanger bay, but it provides the colony with a basic Class II highport, and allows them to export what ever MacGuffin led them to settling the world in the first place. Lets go with some unusually hard and beautiful timber.

Another group bought rights for a 0.4G world with a 12 hour day, so find they don't need any super materials to bring along a prefabricated space elevator. It's old and worn now, looking fuzzy with frayed wires, but while they were forced to downgrade to lighter elevator cars with less capacity for safety a few years back, it's still plenty to allow for some basic trade.

An asteroid colony is split between the old quarter and the new O'Neill cylinder that lies buried at the asteroid core, with rising tensions between those who can afford gravity and the lower classes who have to do without.

It's not particularly hard to come up with backwater worlds that have minimal infrastructure, but are capable of supporting tramp freight. And, sure, that timber colony probably has a deal with a shipping company to ship out X amount of timber per month. But so what? Even when 99% of the trade is done through long term deals with megacorporations, there's always that last 1%. Maybe the players end up loading the ship full of hand made furniture or some local plants with pharmaceutical properties, while a massive liner sweeps by to load up on all the timber.

[Ulzgoroth]

Originally Posted by ericbsmith

All of them require infrastructure. Having a booster rocket stage implies a large industrial base on the planet to make and maintain them. While flying into orbit can help, it's basically impossible with a single-stage-to-orbit model, so again you need launch ships to do the initial flying which requires ground support.

And that's the main issue with realistic spaceflight - you can't really have the tramp freighter full of PCs bouncing from backwater planet to backwater planet having fun adventures. Any planet with the industrial base to launch rockets is going to have the rocket industry dominated by large corporations.

Originally Posted by RogerBW

And anything which changes that (like being able to drop a "rocket seed" nanotech package which builds a booster from local materials) will probably not support tramp freighters either.

Eh, there's multiple ways around that.

Biggest, of course, is that tramp freighters aren't about the surface-to-orbit market. So long as they can get cargoes it doesn't matter whether they're delivered by a private beanstalk, a government beanstalk, a massive disposable rocket industry, or SSTO ship's boats. A corporate dominated launch industry doesn't threaten them unless the corporate launchers refuse to provide service.

Secondly, of course, there's no reason STO has to be corporate. It probably has to be big if space trade is going to be a thing, but government-owned is certainly an option. Especially for beanstalk, launch loop, and similar systems where the fixed infrastructure is concentrated in a single collossal component.


Tangentially, you don't need superscience to be able to operate SSTOs that require little ground-side support. SS2 p19's NTR Condor Space Plane demonstrates that. It wants an airfield and a supply of hydrogen, which could be managed by a TL6 surface society! Of course it'll take a lot of flights if you're trying to ferry up a full load for an Outlander freighter (p5-6) using those.

[Fred Brackin]

Originally Posted by Gnaskar

I

Another group bought rights for a 0.4G world with a 12 hour day, so find they don't need any super materials to bring along a prefabricated space elevator.r.

Not this one. Space elevators mass a _lot_.

I'm kind of dubious about the seaplanes too. The first stage is not realy a problem but it's less help than soem people think too. The likely problem is that you seem to have the second stage/orbiter being a seaplane as well and I don't really think a hypersonically streamined shape is going to do well with a boat-shaped underside.

If you do look for space planes with rounded bottoms the first one you're likely to find is that one that made Col. Steve Austin into a secret government agent.

[ericbsmith]

Originally Posted by Ulzgoroth

Eh, there's multiple ways around that.

Biggest, of course, is that tramp freighters aren't about the surface-to-orbit market. So long as they can get cargoes it doesn't matter whether they're delivered by a private beanstalk, a government beanstalk, a massive disposable rocket industry, or SSTO ship's boats. A corporate dominated launch industry doesn't threaten them unless the corporate launchers refuse to provide service.

Secondly, of course, there's no reason STO has to be corporate. It probably has to be big if space trade is going to be a thing, but government-owned is certainly an option. Especially for beanstalk, launch loop, and similar systems where the fixed infrastructure is concentrated in a single collossal component.

Both of these still require huge infrastructure. Which means highly populated worlds. Which tends to edge out the tramp freighter for large megahaulers, whether they're corporate owned or government run or even independently run is rather beside the point - it removes the plausibility of a small ship owned/run by PCs from being able to hop from system to system.

Beanstalks or the use of orbital transfer stations also reduces the ability of PCs to have planetside adventures, which is a primary trope of the sci-fi genre.

Originally Posted by Ulzgoroth

Tangentially, you don't need superscience to be able to operate SSTOs that require little ground-side support. SS2 p19's NTR Condor Space Plane demonstrates that. It wants an airfield and a supply of hydrogen, which could be managed by a TL6 surface society! Of course it'll take a lot of flights if you're trying to ferry up a full load for an Outlander freighter (p5-6) using those.

NTR's have their own set of problems, namely radiation - both from the reactors contaminating the atmosphere in normal use and from contamination from crashed spacecraft reactor's. Any fission reactor is also going to have limited use by non-governmental agencies, since the risks are too high of them being used as a weapon of some sort.

[Ulzgoroth]

Originally Posted by ericbsmith

Both of these still require huge infrastructure. Which means highly populated worlds. Which tends to edge out the tramp freighter for large megahaulers, whether they're corporate owned or government run or even independently run is rather beside the point - it removes the plausibility of a small ship owned/run by PCs from being able to hop from system to system.

Why? That's not how real world tramp freight works. Tramp freight doesn't rely on liners not existing, it only relies on them not satisfying all demand.

While I don't see any actual reason that beanstalks imply megahaulers, if they did it would be to the advantage of the tramps - the bigger the haulers, the more likely that there isn't one covering the time and route that a customer needs.

Originally Posted by ericbsmith

Beanstalks or the use of orbital transfer stations also reduces the ability of PCs to have planetside adventures, which is a primary trope of the sci-fi genre.

Beanstalks don't reduce the ability, just the motivation. Getting a ride down the stalk shouldn't be particularly hard, but there's not a lot of reason to do so since all the business will be at the highport.

Originally Posted by ericbsmith

NTR's have their own set of problems, namely radiation - both from the reactors contaminating the atmosphere in normal use and from contamination from crashed spacecraft reactor's. Any fission reactor is also going to have limited use by non-governmental agencies, since the risks are too high of them being used as a weapon of some sort.

Who's going to say so? The governments on worlds that otherwise have no STO interface options?

If you think nobody will use nuclear reactors in space, yeah, that does limit a lot of things...

[Agemegos]

Originally Posted by ericbsmith

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Beanstalks or the use of orbital transfer stations also reduces the ability of PCs to have planetside adventures, which is a primary trope of the sci-fi genre.

If the PCs are the crew of a commercial spaceship, that is. But PCs in a sci-fi game no more need to be the crew of a tramp starship than PCs in a modern game need to be commercial aircrew. I’ve been running campaigns of planetside adventures, in a setting where starships unload their passengers and cargo to orbital ports and elevator facilities, for thirty-four years with no trouble. My trick has been to specify PCs who have a job to do on planets rather than a job to do in space, and not burden them with their own spacecraft.

Besides, superscience is another a primary trope of the sci-fi adventure genre. Few of us are ever going to run a sci-fi campaign of planetary adventure without interstellar travel, and once you’ve swallowed that camel, why balk at the gnat of ground-to-orbit lighters with fusion-powered steam rockets?

[Gnaskar]

Originally Posted by Fred Brackin

Not this one. Space elevators mass a _lot_.

The weight scales super-linearly with required length, and linearly with gravity. Length scales to the power of 1.5 with orbital period.

Space elevators on Earth might be extremely heavy, ranging from 17ktons to 1.6Mtons, depending on available tensile strength. On other worlds, they can be significantly lighter. We might be imagining very different things when we say "colony", but for me investing 10 ktons into orbital infrastructure is a sensible thing for a colony to do.

Originally Posted by Fred Brackin

I'm kind of dubious about the seaplanes too. The first stage is not realy a problem but it's less help than soem people think too. The likely problem is that you seem to have the second stage/orbiter being a seaplane as well and I don't really think a hypersonically streamined shape is going to do well with a boat-shaped underside.

I'm not assuming a launch platform first stage, like the ones we have today. I'm talking a full blown rocketplane stage with 10 times the mass of the upper stage and 70-80% propellant. Somewhere in the 3-4km/s delta V range, off the top of my head. And that's assuming methane/lox or hydox. If metallic hydrogen is available, it can do far better. Though even with methane/lox, it would be an SSTO with 10% cargo on a Mars sized world, so it's plenty capable on its own.

The second stage doesn't really need wings, to be honest; a capsule shape with side mounted engines would do. You could even mount the engines behind protective covers if you're worried about salt water. Since it doesn't need to work in atmosphere, my preference would be to give it inflatable propellant tanks. But if your suspension of disbelief can't handle extruding pontoons through a heatshield, it probably isn't going to like inflatable tanks.

Would something like this work on Earth? Probably not. It could in theory, but not with any margin, so it's probably better to reserve this concept for worlds that take about a km/s less to orbit.

Originally Posted by ericbsmith

Both of these still require huge infrastructure. Which means highly populated worlds. Which tends to edge out the tramp freighter for large megahaulers, whether they're corporate owned or government run or even independently run is rather beside the point - it removes the plausibility of a small ship owned/run by PCs from being able to hop from system to system.

I disagree. In a multiworld setting, you don't need to build everything on world. Worlds with smaller colonies can import advanced launch structures from the bigger central worlds. If there aren't at least some highly populated worlds, where are your PCs getting a cheap secondhand ship from? Also, increased automation can make it practical for smaller colonies building bigger bits of brute infrastructure, while also making ships cheaper.

Megahaulers are only useful if they can fill their holds at their target port. So you aren't going to see them visiting ports where the beanstalk can only take 10 tons per hour, since it would take that beanstalk a decade to lift up a million tons. But the 300 ton cargo bay on a tramp is just right for a day spent transferring cargo.

Originally Posted by ericbsmith

Beanstalks or the use of orbital transfer stations also reduces the ability of PCs to have planetside adventures, which is a primary trope of the sci-fi genre.

Roughly half the Traveller plots I've read start with contriving some reason to separate the PCs from their ship and leave them stranded on a planet. If the campaign starting point is that ships can't land and they're always going to have to take a transfer ride to visit the surface, that's a whole lot easier to arrange.

Realistic spaceships are cramped and often don't have gravity. Most crews are going to take shore leave whenever they have the option. Especially on short sleeve worlds.

[Fred Brackin]

Originally Posted by Gnaskar

T
Space elevators on Earth might be extremely heavy, ranging from 17ktons to 1.6Mtons, depending on available tensile strength. On other worlds, they can be significantly lighter. We might be imagining very different things when we say "colony", but for me investing 10 ktons into orbital infrastructure is a sensible thing for a colony to do.



I'm not assuming a launch platform first stage, like the ones we have today. I'm talking a full blown rocketplane stage with 10 times the mass of the upper stage and 70-80% propellant. Somewhere in the 3-4km/s delta V range, off the top of my head. And that's assuming methane/lox or hydox. If metallic hydrogen is available, it can do far better. Though even with methane/lox, it would be an SSTO with 10% cargo on a Mars sized world, so it's plenty capable on its own.

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For the space elevator it was the tramp frieghter bringing one with them that I believed the weight to be too high.

If you're actually planning a giant hypersonic rocket-powered seaplane that is the point where my suspension of disbelief fails. It'd be a _lot_ easier to build one really long runway like KSC has/had for the shuttle than it would be to build a hypersonic boathulled flying machine.

[scc]

OK guys, first of all it's SPACEplane, not SEAplane we're discussing at the moment, the two are very different things.

And the reason spaceplanes are attractive is that the booster stage can use jet engines, which use way less fuel.

Originally Posted by Agemegos

If the PCs are the crew of a commercial spaceship, that is. But PCs in a sci-fi game no more need to be the crew of a tramp starship than PCs in a modern game need to be commercial aircrew. I’ve been running campaigns of planetside adventures, in a setting where starships unload their passengers and cargo to orbital ports and elevator facilities, for thirty-four years with no trouble. My trick has been to specify PCs who have a job to do on planets rather than a job to do in space, and not burden them with their own spacecraft.

It's a sacred cow of space gaming for some reason

[Gnaskar]

Originally Posted by Fred Brackin

For the space elevator it was the tramp frieghter bringing one with them that I believed the weight to be too high.

If it wasn't clear, it was brought in with the colony ship, much like the high port in the first example. Just because we want things for the players to do, that doesn't mean they have to do everything in the setting.

Originally Posted by Fred Brackin

If you're actually planning a giant hypersonic rocket-powered seaplane that is the point where my suspension of disbelief fails. It'd be a _lot_ easier to build one really long runway like KSC has/had for the shuttle than it would be to build a hypersonic boathulled flying machine.

First, it doesn't need a boathull. Very few sea planes use them. Pontoons or hydrofoils would be plenty good enough, and those can be retracted in flight. Secondly, a runway requires effort at the colony. Designing and building a space plane that can take off and land at sea requires effort at the world that sent off the colony, which likely has a lot more resources. And a standard design that works on most garden worlds can divide the design costs out among a lot of customers.

Third, we are discussing science fiction, not what we could do today. Responsive structures that can handle both hydrofoil travel and supersonic flight aren't magical impossible machines that could never exist. They'd likely be easy compared to whatever it took to get people to set up a small colony on an uninhabited world with free oxygen in the atmosphere and liquid water. Since there are no such worlds left in our solar system, we have to assume this is a civilization that has or has had access to interstellar flight, at which point they're likely able to do a few things that would be difficult for us to replicate.

But if the seaplane part is too much, feel free to reimagine the design as a VTOL instead. Same basic concept; a fully reusable two stage vehicle capable of landing on and taking off from undeveloped terrain with somewhere around 8km/s of delta V. In either case, it's designed and built by a core world, and sold to colony expeditions. For low gravity worlds, the first stage is used as an SSTO, while heavier worlds include the kick stage, which is ejected somewhere just above the planet's Karman line and lands via heatshield and parachute.

If you want a universe where tramp freighters make sense, you definitively want to have core worlds that make cutting edge high tech colony gear that needs to be transported to worlds which don't have the infrastructure to support megafreighters or regular visits by liners.