Wanted: Curmudgeony Grognards (to talk TL 5-7 Rockets)

[Grav_Moped]

The Lunar base is necessary to manufacture fuel, parts and power satellites (they have already produced a prototype made entirely from Lunar minerals).

The question is will it be cheaper for Space X to build lots of Starships on Earth or will it be cheaper for them to put the manufacturing on the Moon?

150 tons of manufacturing equipment per launch soon adds up to a Starship production facility on the Moon.

150T up. How much after landing (and taking the lander back up?) The thing about Starship is that it's easy to produce using ordinary manufacturing infrastructure here on Earth. You'd need to replicate almost that entire manufacturing infrastructure on the Moon to do it.

Not saying it's impossible, just that it's not as easy as it may appear.

 

[mike wightman]

If Musk is serious about his million people on Mars then Space X needs to manufacture a few thousand Starships and fuel production on the Moon, which will be transported to a fueling station in Earth orbit.

From what I have read it will cheaper to build a Lunar base and manufacture fuel then to ship all the fuel needed into LEO than it will be to ferry the fuel from Earth.

 

[AnotherDilbert]

150T up.

150 t to LEO, not remotely that to the Moon and back.

But with trivial cost per launch...

 

[Baroun Tardis]

150T up. How much after landing (and taking the lander back up?) The thing about Starship is that it's easy to produce using ordinary manufacturing infrastructure here on Earth. You'd need to replicate almost that entire manufacturing infrastructure on the Moon to do it.

Not saying it's impossible, just that it's not as easy as it may appear.

And suddenly this thread, much earlier than historically expected, crosses paths with the "tech level distribution" thread

"Yeah, Earth is TL8+, but the Moon is only TL2, as far as local production is concerned"

 

[mike wightman]

We can't make air/rafts or fusion power plants...
Earth is at best TL7.8

Once we put chip fabricators, metal refining and manufacture on the Moon it too will be 7.8

 

[Grav_Moped]

We can't make air/rafts or fusion power plants...
Earth is at best TL7.8

Once we put chip fabricators, metal refining and manufacture on the Moon it too will be 7.8

... and the people to run them. And places for them to live, and food, water, and air...

We can. We probably will, eventually. It's still a lot more complicated than it seems.

 

[Spinward Flow]

"Yeah, Earth is TL8+, but the Moon is only TL2, as far as local production is concerned"

Luna (current day) UWP = Y210000-0 Non-industrial.

 

[mike wightman]

What about the alien base population on the far side?

 

[Captain_Ahab]

The problem with the gun solution is barrel erosion. You can fire a couple dozen rounds, then have to totally rebuild the barrel as the tolerances aren't there any more. For example, with the WW 1 Paris Guns, barrel erosion was so severe that the shells fired were sequentially numbered and each round's driving bands increased slightly in diameter to account for barrel wear. You could get about 75 rounds out then you had to swap out the barrels and rebuild the worn one.

I also don't know if you could fire live payloads like people into space that way.

in real life, yes

in game rules, no

imagine if real life experiences were applied to all traveller tech with equal vigor...

 

[Enoki]

in real life, yes

in game rules, no

imagine if real life experiences were applied to all traveller tech with equal vigor...

I thought one of the basic design tenants of Traveller was that to the extent possible, it would be based on known engineering, physics, science, etc. Of course, some of it can't be, but to the extent possible it should be.

 

[AnotherDilbert]

I also don't know if you could fire live payloads like people into space that way.

No way?

Back of the envelope:
A howitzer accelerates a round to 300 m/s in the 5 m barrel.
With constant acceleration that is d = at², so a = d/t²

v = at, so t = v/a.

d = av²/a² = v²/a, so a = v²/d = 300²/5 = 18000 m/s² ≈ 1800 G.

Anything alive becomes a flat film of fluids...

 

[atpollard]

I also don't know if you could fire live payloads like people into space that way.

If you go with a coil gun and slow the Acceleration while extending the barrel.
People can tolerate 10 G for "minutes" with the correct orientation, so let's set that as our acceleration.
8 km/s Orbital Velocity requires a 320 km long Barrel and 10 G for 80 seconds.

You could "fire" a 20 dTon Launch into orbit as your projectile through a long series of rings.

 

[kilemall]

If you go with a coil gun and slow the Acceleration while extending the barrel.
People can tolerate 10 G for "minutes" with the correct orientation, so let's set that as our acceleration.
8 km/s Orbital Velocity requires a 320 km long Barrel and 10 G for 80 seconds.

You could "fire" a 20 dTon Launch into orbit as your projectile through a long series of rings.

Not exactly starport D infrastructure.

 

[kilemall]

Hmm, could mention a Star Wars ‘solution’ to all this- starport push tech. Think repulsor bays that help boost.

Was mentioned in the novelization of the first movie, I don’t think they kept it up.

Again, messes with the escape Mos Eisley plot points players desire.

 

[Spinward Flow]

Again, messes with the escape Mos Eisley plot points players desire.

Not at all. The "freighter that blasted out of Mos Eisley" did so on unplanned short notice under its own power, rather than relying on an assist from port infrastructure.

 

[Baroun Tardis]

Not at all. The "freighter that blasted out of Mos Eisley" did so on unplanned short notice under its own power, rather than relying on an assist from port infrastructure.

It would be logical to presume that the fastest ship in the galaxy would have sufficent thrust to do that...

 

[Condottiere]

A thought comes to me: how much would it cost me to get my spacecraft in orbit, because a repulsor catapult assist is unlikely to be free.

 

[whartung]

If the payloads are such that they can withstand the centrifugal loading during launch.

This is a solved problem for them. I saw a great video with a bunch of counterpoints to a lot of the armchair internet hand wringing of how unpossible this is. It's a really cool system.

The G problem even surprised them after some testing and some analysis in how little of a problem it actually turned out to be. Obviously it will limit payload design, but not in any practical way for the types of payloads they plan on flinging up. Essentially solid state satellites.

It's also a boost technology. The payload include rockets, motors, fuel, etc. The spin part handles the "hard" part of the initial boost, once higher up the actually booster is lit to take the payload to higher orbit.

 

[Spinward Flow]

A thought comes to me: how much would it cost me to get my spacecraft in orbit, because a repulsor catapult assist is unlikely to be free.

That's easy ... orbital interface costs Cr10 per ton of cargo (LBB2.81, p9).

200 ton Free Trader ... costs Cr2000 for a one way trip (up or down) between surface and orbit ... because the ship is "just cargo" in that respect.

The "how" of making that transit is left wide open.
Whether it means loading your Free Trader into another craft or using a "gravitic catapult" in order to make it happen is a matter of fluff text and "flavor" for the local technological base. Point being that there are different ways to achieve the same results (rockets, gravitics, thruster plates, catapults, hangar bay/cargo hold, etc.) ... but in terms of Cost Of Service, that ought to be fixed at Cr10 per ton.

 

[Condottiere]

That's an extra two kilostarbux that the freetrader captain might be loath to part with.

You'd really need a good reason to go dirtside, if you can't pull out with your boo[st]raps.