I was thinking of something that was a bit easier to figure on the fly, but that works too.
Using Traveller ships and deck plans for ships with reaction drives
- Thread starter Thot
- Start date
I was thinking of something that was a bit easier to figure on the fly, but that works too.
I recall an OTU reason that X-boats were intentionally left at J-4 and a secret fast secondary system at J-6 so there could be advance notice for major events and time to prepare before the news became general.
LeperColony
Traveller Card Game Dev Team
Yeah, I think that's in Library Data or something.
Also, cost may be an issue, but more important, the number of locations that can service/repair/maintain J-6 engines may be rarer than J-4.
The problem with that is that it creates an infinite power source: Move water up using contragravity, switch off contragravity, collect the potential energy from the fall, start over.
Hm. Unless the drive doesn't actually make anything lighter or move anything, but merely holds a ship in place, as if standing on an invisible surface... then we'd have enough time to accelerate very slowly. reducing the energy requirements.
That was more or less my thought.
No. The Contragravity device would itself require power to operate, and would likewise produce waste heat as a byproduct of its operation.
Note that where electromagnetic fields are involved, you can do the exact same thing using maglev, and it does not violate conservation of energy.
Well, that might work. However, after having done a few computations, and using modern ship reactors as a reference (which seem to be in the range of 75 tons per MW of power output), I must say I will have to invent some kind of super-power source anyway if I want to stick with electric propulsion and use an exhaust velocity of 120km/s as planned.
In other words, the whole plan doesn't work even WITH contragravity, unless I am willing to ascend to orbit over the course of several years instead of hours or days.
It is probably a lot easier and more plausible to use an old-fashioned chemical rocket with an exhaust velocity in the usual 4500m/s range.
For a 1000 ton-ship (payload), that would require roughly 15,670 tons of reaction mass in order to reach the 12km/s I am aiming for.
In other words, using Traveller deckplans only works if I carry them on a gigantic rocket in the way the old space shuttles were. And that's not going to be available on a foreign, uninabited planet.
Unless.... I can find a chemical rocket fuel that has a density in the range of 155 g/cm³. That is the about eight times the density of heavy metals like gold or osmium...
Maybe a superscience method to increase a material's density?
Last edited:
I recall that as being the non-canonical explanation. I haven't seen it in canon, but there is a lot of published work out there that I've never had the opportunity to set eyes on. I do something like that in my TU: there's a base-to-base network of communications (and high priority passenger transport) parallel to the x-boat net to ensure all bases are communicating with each other and with the core at best possible speed. Military and sector government communications run along the military net, other communications run through the X-boat net or through the trade net, which is slower than the X-boat net since it relies on the network of freight ships and trade routes.
Since the bases are not all a perfect six parsecs apart, I also use an Ultra-level communications line for communications that have to go as fast as possible to the sector dukes or sector admirals of distant sectors, or from such persons to the Emperor. Basically pony express model, but the stations are at 6 parsec intervals and therefore sometimes in some difficult places, the ships hanging out at station waiting to jump are task forces consisting of a J6 light cruiser and some J6 escorts, and the tenders are correspondingly larger since they have to double as a rudimentary base. Lets them do things like transporting key individuals in relative comfort.
mike wightman
SOC-14 10K
The Traveller Adventure details the secret jump 6 courier network - in the SM it is called Imperiallines.
Everyone knows the IN uses jump 6 couriers, it is a closely guarded secret that:
This is how Norris was able to elevate himself to Archduke ahead of the plebs finding out about the assassination of Strephon.
I'll go scour MT sources and see if I can find it.
Everyone knows the IN uses jump 6 couriers, it is a closely guarded secret that:
It would be in a MT source (if anything is specifically mentioned) that details the deliberate restriction of the x-boat system to jump 4, while the secret government courier service is maintained at jump 6.
This is how Norris was able to elevate himself to Archduke ahead of the plebs finding out about the assassination of Strephon.
I'll go scour MT sources and see if I can find it.
So I guess I will just attach a really, really big chemical rocket to all ships, and give ships the means to synthesize more fuel once landed.
Gas giant refueling should also work if the process works fast enough and both hydrogen and oxygen are available in the system (which can be reasonably expected).
For a delta v of 12km/s, the total liftoff mass of the ship should consist of at least 93.1% of rocket fuel. For a Beowulf free trader (200 dtons, 1,000 mass tons), that means an additional 19,000 dtons of attached rocket - while that seems massive, it is, in the end, easier to handwave this away as "cheaper through tech progress" than to alter the laws of physics.
mike wightman
SOC-14 10K
If you are taking off from a planet with an atmosphere then use the atmosphere as reaction mass, i.e. a jet engine.
Your hull form will have to be a hypersonic lifting body.
Switch to internal reaction mass once the atmosphere thins to the point that forward velocity and intake can not get enough gas on board.
Your engine has to be able to switch from jet to rocket mode - handwave of beyond current technology.
Your hull form will have to be a hypersonic lifting body.
Switch to internal reaction mass once the atmosphere thins to the point that forward velocity and intake can not get enough gas on board.
Your engine has to be able to switch from jet to rocket mode - handwave of beyond current technology.
Actually, I linked a system like that earlier in this thread.
But the amount of Delta-V you save by that is not even half of what is required (you will not be able to go much faster than Mach 5 with that before you run out of surrounding air, I'd guess). And it's a system that won't work everywhere.
By contrast, just attaching a giant rocket to the backside of the ship will work everywhere and will be sufficient. For liftoff from an Earth-sized planet with a 200dton-ship, you'd need a rocket of 100 meters length and 60 meters diameter, but while such dimensions seem uncomfortable, if we assume that this is tried, tested and cheap technology, it is actually doable. The ship could land in vertical position, which would justify its general layout, or it could land on its tail (like SpaceX's ships) and then just move the "deck plan stage" into a vertical position near the ground fir easy planetside operation.
But the amount of Delta-V you save by that is not even half of what is required (you will not be able to go much faster than Mach 5 with that before you run out of surrounding air, I'd guess). And it's a system that won't work everywhere.
By contrast, just attaching a giant rocket to the backside of the ship will work everywhere and will be sufficient. For liftoff from an Earth-sized planet with a 200dton-ship, you'd need a rocket of 100 meters length and 60 meters diameter, but while such dimensions seem uncomfortable, if we assume that this is tried, tested and cheap technology, it is actually doable. The ship could land in vertical position, which would justify its general layout, or it could land on its tail (like SpaceX's ships) and then just move the "deck plan stage" into a vertical position near the ground fir easy planetside operation.
FF&S had an engine that could do this, but I don't remember the name.
mike wightman
SOC-14 10K
Are you allowing for a breakthrough in small fusion reactors? If so you can use a fusion steam kettle reliant on atmospheric gasses to achieve the atmospheric velocity of mach 5-12 and then switch to internal fuel for the push to orbit.
You can then go with electric/plasma propulsion for long duration in space, but keep some gas in reserve in case you need to use the rocket thrust eg combat maneuvering
You can then go with electric/plasma propulsion for long duration in space, but keep some gas in reserve in case you need to use the rocket thrust eg combat maneuvering
The speed that a transorbital ship needs to be able to do is well in excess of 11km/s.
Mach 10 (which is optimistic) would be 3.4 km/s. I would still need a giant rocket for all that remains, and I'd add a more complex and expensive engine to the bill.
A thought, though: More advanced ship might use giant force field tanks for the rockets.
Mach 10 (which is optimistic) would be 3.4 km/s. I would still need a giant rocket for all that remains, and I'd add a more complex and expensive engine to the bill.
A thought, though: More advanced ship might use giant force field tanks for the rockets.
AZHRAE - Advanced Zero to Hypersonic Regime Air-breathing Engine (IIRC).
You could always go ground-based repulsor lift like Star Wars.
OP, here is a reaction takeoff discussion I did-
http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=34502
http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=34502
Gracias, that's what I was thinking of.
