mike wightman
SOC-14 10K
I don't understand your reasons.
Skylon will be cheaper than a rocket.
The Chemical Rocket Third Imperium
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Skylon will be cheaper than a rocket.
mike wightman
SOC-14 10K
No probs, I've posted the wiki article at least twice - but here is the summative cost analysis from the article:
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.
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.
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.
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.
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.
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.
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.
Because you can't have an interstellar empire without interstellar travel. But you can have one without gravitic technomagic.
Side-effec-free drugs? I'd rather believe in gravitics or FTL :devil:
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.
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...
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 probably the only part of 3I that will not be changed...
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)
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...
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.
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.
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...
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 :CoW:
Well, let us agree that "side-effect-free" is what the label sais. :rofl: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.
That's true. Fortunately, for this little chemical rocket thought experiment, we can just adjust the behavior of the jump drive.
Well, my country doesn't.
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..
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.
But that's something where higher tech levels can conceivably help.
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.
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.
Agreed. One thing to think about though: Launch catapults are quite an interesting thing under such circumstances, both for the carrier and the fighter.
I guess that mostly depends on the new safe jump distance compared to spinal weapon ranges.
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.
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.
I guess people who sign up for a Chemical Rocket Third Imperium game will be quite interested in it.
[FONT=arial,helvetica]A 1000 ton vessel by HG that is at Power Plant 2, anemic by many standards, would work out to 20 EP, which is 5 GW.
So accepting your numbers as sacrosanct for the purposes of this demonstration, that means I can move 30.8 kg with that power plant.
30.8 x [FONT=arial,helvetica]0.018 m/s² gets us [/FONT][FONT=arial,helvetica].5544 [/FONT][FONT=arial,helvetica]m/s². Not spectacular, but not useless either.[/FONT][/FONT]
The other part is I don't quite how 4x impulse thrust output translates to having to have an ion drive. Metallic Hydrogen would be used as a chemical impulse, not as ion mass, it's just an exotic with greater cost, but possibly greater rewards for military or special purpose ships.
So accepting your numbers as sacrosanct for the purposes of this demonstration, that means I can move 30.8 kg with that power plant.
30.8 x [FONT=arial,helvetica]0.018 m/s² gets us [/FONT][FONT=arial,helvetica].5544 [/FONT][FONT=arial,helvetica]m/s². Not spectacular, but not useless either.[/FONT][/FONT]
The other part is I don't quite how 4x impulse thrust output translates to having to have an ion drive. Metallic Hydrogen would be used as a chemical impulse, not as ion mass, it's just an exotic with greater cost, but possibly greater rewards for military or special purpose ships.
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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.
When 2300AD was first written, it wasn't a deviating timeline; the Soviet Union still existed.
(Oddly, I've seen some T2K grognards who now have to make changes to the backstory to play the game. They just can't handle alternate history, something I have issues with as long as it's either plausible or fun)
OTOH, the stutterwarp drive might be an issue for you. Inside a slight gravity well it becomes a STL drive not needing reaction mass but in a strong to moderate gravity well -- hmm, if you get to close to a world, it stops working.
Are we talking dtons or mtons?
But anyway: It is simply insufficient, unless you are already in an orbit. And we are assuming a 100% efficiency of the drive here, which is likely illusionary.
If you want your ship to launch as an airplane, you will at least need 1 m/s² and a long runway (for atmospheric takeoff, in a vaccuum, you are out of luck anyway - this ship couldn't even take off from the moon). That would translate to almost 10 GW., which even with Traveller's standard assumptions, is quite a number that eats away a lot of payload.
In order to keep your hydrogen metallic, you need more than 100 GPA of pressure. (I just found a document stating 300 GPa were not sufficent in experiments) A regular atmosphere has 100 kPa, so the pressure you need keep your MH2 at is at least 4 million (!) atmospheres, for an energy release of (apparently) 216 MJ/kg, which would translate to an exhaust velocity of just under 21000 m/s.
If you can build a light tank that can carry metallic hydrogen (imagine the pressure...), and have the industry to produce metallic hydrogen, that might be an option. But honestly, I don't see how that should be possible, and especially not when landing with your ship on a distant planet, be it as a military expeditionary force, a merchant, or an explorer.
I am all for considering alternative chemical fuels, but they need to be manageable. And the fact remains that 4,500m/s is about the best exhaust velocity that can be done with chemical reactions.
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Pseudovelocity drives of that kind could actually be a way if there is physics to be discovered that we don't know yet. We need some kind of FTL anyway, and if you have it, you will use it whenever useful. Note how the CR3I would probably use a lot more in-system jumps than in the OTU. That'd be one compromise I'd be willing to make, though if we would want to go all the way, we'd simply assume it works everywhere, even on the ground, and explain all kinds of craft with that, from spaceships to hovering cabriolet gliders.
(BTW, I bought the 2300 AD Mongoose PDF yesterday. Fun read.)
Traveller TL's 10+ all are built upon the assumption that gravitics
- makes fusion more efficient,
- space travel much safer (in part by reducing travel times by multiple orders of magnitude, in part by use of deflectors to prevent microbody abrasion, in part by no exposure to the effects of Zero G)
- Space travel accessible
- high recoil weapons more controlable
- allows breakthroughs in jump tech
- makes what little stealth in space is physically possible impossible
- Allows neutrino detection
Your "Chemical Rocket Imperium" will look NOTHING like the 3I unless you invoke other magic.
Traveller's prices are based soundly in 1976 US dollars... bunker fuel was around $12.something per barrel, and 8.5 barrels to the metric ton (CT1E was mass based), so the unrefined fuel was roughly equivalent to bunker oil.
I suspect the refined fuel price is avgas... Note that LHyd was much more expensive... if you're reducing fuel costs below that, you've broken the economic models (which are not great to begin with, but are the foundation upon which many parts are hung)...
The costs for hulls are good fits for 1976 era shipbuilding. Marc assumed a pretty much equivalent cost to base wage progression across tech levels. Fiddle with those, and all the prices are busted; either because the other good are too expensive in proportion, or the overall cost of EVERYTHING drops proportionally (which is, really, no effect at all, other than ink wassted)...
Marc has said several times, "Follow the Money"...
If you're not looking for constructive criticism, just report your thread, and I'll close it. If you are, understand that the traveller rules are the way they are for a reason, explain what you're changing, and be prepared for the roast of your ideas that follows.
If all you want is a "What a cool idea" response set, you're on entirely the wrong forum.
Stutterwarp is strictly orbit to orbit. For surface to orbit, you need a craft with reaction drives. A couple of worlds have beanstalks.
Oh, and no gravatics technology. Best any race has is spin gravity.
You are talking about the OTU's tech levels, I presume.
Most certainly there will be major differences, that is, after all, the point of the thought experiment: To figure out what those differences will be.
I was roughly aiming for the basically same transfer cost per ton, so due to the higher consumption, my goal was to achieve about the same expenditure, without ending up with too uneven numbers. 1 Credit per ton of fuel (both LH2 and LOX) seems right to me from that point of view.
What I want is valid arguments. If I believe they are not valid, I will point that out. If that is unwelcome here, then just say so, and I'll leave for good.
mike wightman
SOC-14 10K
I'm enjoying this thought experiment - it makes for an interesting setting.
I have spent more time than I should over at atomic rockets and hunting down real world rocket info thanks to this thread (not to mention brushing up on maths).
Yes, I am reading the setting book from Mongoose (using Mongoose Traveller rules) right now. Really nicely done!
But thinking about it, for keeping a "realistic" feeling, a jump drive is probably a better fit, because it has less impact on all other forms of travel than a warp drive of any kind, even when one includes such gravity limitations to both - that way, you either move in normal space, following normal physics rules, or you do not move at all.
It's true that high pressures are involved.
In the regular Traveller tech there are fusion containment of some sort, cheap large scale power when and where needed, extensive gravitic manipulation which could be turned to that sort of pressure creation, and nuclear force manipulation, the combination of which would likely lead to materials technology and chemical process engineering that we can scarcely conceive of.
Gigapascal pressure generation will likely be trivial.
You may have missed the part about Metallic Hydrogen where the theory is once it's formed as a metal, it's metastable and will not require excessively expensive continuation of pressure.
The bigger problem might be that it is a highly energetic fuel that might be that much more explosive when struck by lasers or missiles.
As to tech level, that's generally speaking the sort of technology that has run through the whole series since the beginning without reference to the OTU, with side ventures like Fusion+ being more version/milieu dependent.
In the regular Traveller tech there are fusion containment of some sort, cheap large scale power when and where needed, extensive gravitic manipulation which could be turned to that sort of pressure creation, and nuclear force manipulation, the combination of which would likely lead to materials technology and chemical process engineering that we can scarcely conceive of.
Gigapascal pressure generation will likely be trivial.
You may have missed the part about Metallic Hydrogen where the theory is once it's formed as a metal, it's metastable and will not require excessively expensive continuation of pressure.
The bigger problem might be that it is a highly energetic fuel that might be that much more explosive when struck by lasers or missiles.
As to tech level, that's generally speaking the sort of technology that has run through the whole series since the beginning without reference to the OTU, with side ventures like Fusion+ being more version/milieu dependent.
