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In My Traveller Universe Detail what parts of Traveller you do (or don't) use in your campaign.

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  #41  
Old July 26th, 2017, 12:47 PM
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Originally Posted by Thot View Post
I have considered them all. They fail, for various reasons.
I don't understand your reasons.
Skylon will be cheaper than a rocket.
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Old July 26th, 2017, 12:56 PM
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I don't understand your reasons.
Skylon will be cheaper than a rocket.
Can you point me to some numbers on the projected cost per kg of payload?

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  #43  
Old July 26th, 2017, 01:21 PM
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No probs, I've posted the wiki article at least twice - but here is the summative cost analysis from the article:
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the cost per kilogram of payload carried to low Earth orbit in this way is hoped to be reduced from the current £1,108/kg (as of December 2015), including research and development, to around £650/kg, with costs expected to fall much more over time after initial expenditures have amortised
So if rockets can be made as cheaply as you suggest, these will be even cheaper

Now for the sci-fi bit - TL 9+ with advances in material technology etc the engine can have third mode added thanks to a configurable inlet to allow hypersonic flight in atmosphere of up to mach 12, thus increasing the payload even further.

These become your interface vessels of choice, backed up by rockets for worlds without an atmosphere that would allow for the use of these engines.
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Old July 26th, 2017, 01:48 PM
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As noted Traveller fusion plants output a lot of juice, which coincidentally if the M-drive is in use, uses up most of the power.

CT High Guard has two power settings, all weapons and defenses powered and what's left for agility (evasion and/or vee), and all power to the Mdrive for escape.

So power is NOT a problem.

If you are going to insist on not having that tech too, at a certain point you aren't using Traveller tech trees at all.
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Old July 26th, 2017, 02:00 PM
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Also, if so many technologies are being bypassed because they are considered magical, how can jump drives (or any FTL drive) still be used?
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  #46  
Old July 26th, 2017, 02:15 PM
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Originally Posted by mike wightman View Post
No probs, I've posted the wiki article at least twice - but here is the summative cost analysis from the article:
Hm, that number for LEO from more conventional rockets is not correct.

Let us look at what a chemical rocket can do even today - and this is not a projection, this is a purchaseable product (though a bit outside of the range of my personal pocket money, admittedly):

http://www.spacex.com/about/capabilities

They list 62 million dollars for a single launch of the Falcon 9. That launch can carry 4 tons of payload to Mars (!) or 22.8 tons to Low Earth Orbit. That means for LEO, that's a cost of 2720 dollars (2,076 pounds Sterling) per kg for LEO, dollars per kg to Mars. 15,400 dollars (11,774 pounds) to Mars.

Using the Falcon Heavy, the numbers are 90 million per launch, 1411 dollars (10,779 pounds) per kg to LEO. Today, not in ten years if and when the SABRE is actually built. By then, even heavier chemical rocket systems will likely be available, improving the cost ratio even more.

And note that the Skylon really only shines for LEO. The usefulness of the SABRE engine vanishes beyond 50-100 km of altitude, I would guess, when no menaingful amounts of oxygen can be drawn from the air any more.

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So if rockets can be made as cheaply as you suggest, these will be even cheaper
It could certainly be cheaper, but my objection is that the system, merely saves a fraction of the launch cost (and a small one at that), if any at all, adds a lot of complexity (and thus sources of both failure and unforeseen cost) and is basically just a lower stage for an actual space craft of the type we need. And no tech progression will change the basic physics, so the performance will NOT increase as you hope. Not to mention that it isn't even built yet. Much like fusion reactors.

More complex, more specialized, that's two reasons why it is not so easily scaled up in production numbers.
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Old July 26th, 2017, 02:21 PM
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Originally Posted by kilemall View Post
As noted Traveller fusion plants output a lot of juice, which coincidentally if the M-drive is in use, uses up most of the power.

CT High Guard has two power settings, all weapons and defenses powered and what's left for agility (evasion and/or vee), and all power to the Mdrive for escape.

So power is NOT a problem.[...]
So let me do the math for you.

The 162 Megawatts are for ONE kilogram of reaction mass per second, expelled at 18,000 m/s. For a ship that has a mass of 1,000,000 kg (1,000 tons), that means our little ship will accelerate at 0.018 m/s². Double that, and you also need double the energy.

I think we can agree that this is some kind of problem worth noting.
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Old July 26th, 2017, 02:26 PM
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Originally Posted by Brandon C View Post
Also, if so many technologies are being bypassed because they are considered magical, how can jump drives (or any FTL drive) still be used?
Because you can't have an interstellar empire without interstellar travel. But you can have one without gravitic technomagic.
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  #49  
Old July 26th, 2017, 02:34 PM
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Originally Posted by Thot View Post
Instead, there is side-effect-free medication that prevents atrophy and all that.
Side-effec-free drugs? I'd rather believe in gravitics or FTL

Sorry, I had to take it out, but this is a minor issue at worst, as either drugs with bearable side-effects or centrifugal simulated grav (again, as in 2300 AD setting) may well mitigate or solve this problem.

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Indeed. That's why I wrote the battle rider concept, and starships basically staying at the jump point and do force projection via fighters and long-range weaponry from there would probably be a good guess.
And what endurance will those fighters have? what acceleration? will they have beam weapons (needing a larger PP, an so more fuel, even in not much) or missiles (needing payload for them, and if, as I understand, they are in the low-G range, needing to make long trips to reload)?

See tha twithout gravitics, those fighters are likely to be mostly crewed and armed fuel pods...

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Originally Posted by Thot View Post
As an extension of that, there'd probably be "jump ports", space stations at common jump points that allow for refuelling and changing cargo... that's actually something that might even be a worthy idea in the OTU.
If you considere that ships exit jump blindly and keeping their vectors, and the error margin is about 3000 km, setting up those "jump ports" is, IMHO, asking for a collision...

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Is that so? The technofeudal society seems like a near-perfect fit to me. Travel times and cost are, after all, largely unaffected.
That's probably the only part of 3I that will not be changed...

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Originally Posted by Thot View Post
I have reservations about catapults, beanstalks and the like - they have a vast array of problems that are commonly not addressed in the concepts. Among them: Extremely high capital investment required, extremely vulnerable to terrorist attack, warfare, and regular accidents, day-to-day operations are more complicated than many people imagine (as I wrote earlier, if you send something up the beanstalk, you have to send something of equal mass down at the same time, and if that other mass isn't available, you must wait, for just one example), and so on. Also, such installations would not have survived the Long Night.
And nuclear power plants and dams ar also extremely vulnerable to those same threats, yet we keep using them...

As for the beanstals, I guess you don't need this similar mass if you have power enough, and poser is cheap (otherwise fuel could not be, as it is obtained from water by electrolisis, I understand)

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Originally Posted by Thot View Post
Cheap fuel and cheap rockets, however, are easy to achieve, require little individual investment, are naturally redundant (because many people will have them), and allow for players to earn a buck with their own ship anywhere where they might go. Sure, a player ship will seem large compared to Traveller OTU deck plans, but in actuality, the ship they can live in will be the same size - just with a lot more (cheap) fuel attached.
But they need more ship volume fo rthe same payload, and I guess they also need quite a lot of infrastructure to be launched. Probably cheaper to set up, but quite more expensive to operate...

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Originally Posted by Thot View Post
2300 AD has been suggested already, and I have put it on my list for sure. I always found the whole concept interesting, but a deviating timeline and lack of ability made me never grab it. Thankfully, DTRPG has changed that.
I guess you'll find it interesting at least. I'd also advise you to read MT article One Small Step (from HT and also in Challenge magazine issue #45) about pre-gravitic (or no gravitic, in this case) space flight.

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Actually, that would be own concern: Given that I have removed the jump fuel requirement to not make things worse and replaced it with a 1 week cooldown, it should theoretically possible for the Zhodani to have a fleet parked in a comet cloud around Sylea just in case they need it...
What endurance will those ships have? for how long can they stay powered with thier fuel? how much endurance will they have accelerating?

Remember, fuel must include not only Hydrogen, but oxygen too, so using more volume (and weighting quite more) than traveller's fuel.

And I don't expect the ships staying still for a week when they exit jump. THey are likely to send fighters in recon role, to manyever a little, etc., and ,without the capability to recover their fuel, they will become short of it in a few jumps, if they are to have any payload for weponry or fighters.

And if caught short of fuel, they will become stting ducks for the enemy to chase, not being even able to move.

So, I keep my assertion, as you describe it, offensive opperation will be quite limited.

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Originally Posted by Thot View Post
Depends. If you are willing to forego a chance for retreat, you might even require no fuel at all, and simply fall down in drop capsules with parachutes (unless it's a vaccum world, but those are usually smaller anyway).
And who's going to forego the retreat chance? Or will all Marines be sucicide units? How will they be suplied? how will they move once on ground, without gravitics nor interface ships to bring them vehicles?

If they have to walk, taking a planet like terra will take quite a long, even in quite less defended than OTU invasión of Earth...

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Well, on the plus side, planetside combat would be more familiar to players.
There are many games for that. I guess when players want to play a science fiction battle game they are not looking for something familiar
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Old July 26th, 2017, 03:21 PM
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Side-effec-free drugs? I'd rather believe in gravitics or FTL

Sorry, I had to take it out, but this is a minor issue at worst, as either drugs with bearable side-effects or centrifugal simulated grav (again, as in 2300 AD setting) may well mitigate or solve this problem.
Well, let us agree that "side-effect-free" is what the label sais.

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And what endurance will those fighters have? what acceleration? will they have beam weapons (needing a larger PP, an so more fuel, even in not much) or missiles (needing payload for them, and if, as I understand, they are in the low-G range, needing to make long trips to reload)?
With chemical rockets, the actual acceleration isn't much of an issue, it can easily be 30m/s² without much ado. The delta vee, however, would be vital, and in the 10-20km/s range, not more. Relation from payload to fuel mass will probably be around 1:20.

Weapons should probably be standard Traveller stuff of all kinds.

Quote:
[...]
If you considere that ships exit jump blindly and keeping their vectors, and the error margin is about 3000 km, setting up those "jump ports" is, IMHO, asking for a collision...
That's true. Fortunately, for this little chemical rocket thought experiment, we can just adjust the behavior of the jump drive.

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And nuclear power plants and dams ar also extremely vulnerable to those same threats, yet we keep using them...
Well, my country doesn't. :P

But more to the point, a nuclear power plant is a minor risk compared to a beanstalk. Fukushima made a single county uninhabitable, a beanstalk disaster would at the very least kill one ore two continents when the construction collapses and is wrapped around the Earth by planetary rotation..

Quote:
As for the beanstals, I guess you don't need this similar mass if you have power enough, and poser is cheap (otherwise fuel could not be, as it is obtained from water by electrolisis, I understand)
If you don't send down equivalent mass, then the upper part of the beanstalk becomes slower when you send something up, to the point where the Earth starts to rotate faster than the upper end of the beanstalk. As a result, it will be pulled towards the surface, and collide with it disastrously. You could use some kind of thruster to compensate for that, sure. But it would have to be quite some thruster.

Quote:
But they need more ship volume fo rthe same payload, and I guess they also need quite a lot of infrastructure to be launched. Probably cheaper to set up, but quite more expensive to operate...
But that's something where higher tech levels can conceivably help.

Quote:
[...]
What endurance will those ships have? for how long can they stay powered with thier fuel? how much endurance will they have accelerating?
As long as they just keep drifting in space (or in some solar orbit, or even just falling towards the local star very slowly), they'd probably last for as long as the crew likes. But I guess food supply might become an issue, so that danger would probably be manageable.

Quote:
Remember, fuel must include not only Hydrogen, but oxygen too, so using more volume (and weighting quite more) than traveller's fuel.
Density of liquid hydrogen: About 70 kg/m³.
Density of liquid oxygen: 1,141 kg/m³.

So the oxygen is much easier to store than the hydrogen. Also, its mass is included in all the delta V calculations, so that's not a problem.

Quote:
And I don't expect the ships staying still for a week when they exit jump. THey are likely to send fighters in recon role, to manyever a little, etc., and ,without the capability to recover their fuel, they will become short of it in a few jumps, if they are to have any payload for weponry or fighters.

And if caught short of fuel, they will become stting ducks for the enemy to chase, not being even able to move.
Agreed. One thing to think about though: Launch catapults are quite an interesting thing under such circumstances, both for the carrier and the fighter.

Quote:
So, I keep my assertion, as you describe it, offensive opperation will be quite limited.
I guess that mostly depends on the new safe jump distance compared to spinal weapon ranges.

Quote:
And who's going to forego the retreat chance?
People who are sure to win or people who have no choice but to try.

I would propose that attacks on planetary systems are a thing you only do when outnumbering the defenders vastly anyway. Even in the OTU. After all, attacking with at least 3:1 is a good old and proven rule of thumb. Another one is: You don't attack when you're not sure to win, unless you are very desperate.

Quote:
[...]
How will they be suplied? how will they move once on ground, without gravitics nor interface ships to bring them vehicles?
Drop pods. If your Navy has space superiority, it can bring in more troops and vehicles (both air and ground, possibly even seagoing components) with troop transports that travel from the jump point to planetary orbit. Once the planet is secured, the relaunch rockets land, refuel and bring everything up again.

Yes, the scale of such operations is mind-boggling. But so is the size of the Imperium.

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There are many games for that. I guess when players want to play a science fiction battle game they are not looking for something familiar
I guess people who sign up for a Chemical Rocket Third Imperium game will be quite interested in it.
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