Engineering!

[Woas]

Just like the little guy from the old Command & Conquer game who would yell that out when you selected him, I'm here to pick some brains around here about the stuff that is under a spaceship's hood.


Well, I understand that the power-plant of a ship is a fusion reactor that runs on whatever form of hydrogen isotope you care to use. The energy created with this power-plant is then run off the various electrical equipment of the vessel (computers, lights, life-support, sensors, etc.). The other important piece of ship equipment, and the one I am really asking about is of course these so called "thrusters". Here in the real world, seafaring ships have power-plants (sometimes nuclear ones even) and propellers or waterjets in place of thrusters. I may have slept through high-school physics class but I know that spinning propellers are obviously not going to push a spaceship in outer space!

So then, in your Traveller game what are thrusters? What real world or sci-fi sources do you pull from to explain how space vehicles move about in vacuum? Or perhaps there was an older Traveller book that gave it some explanation you could share with me.


Another topic I'd like to discuss is the functionality of tail-landing starships. I understand what it means, that when the ship is landing on a surface, it effectively is sitting on it's 'tail' instead of 'belly' but how does this effect the people/cargo inside? What do tail-landing ships look like and how do they come in from vacuum to an atmosphere/gravity? I gather the Mercenary Cruiser from the core book is supposed to be a tail-sitter but the deckplans are kind of confusing as it seems that, in space the ship would always be flying 'up'.


Well that's all my questions for now. I look forward to reading your responses.

 

[rust]

As for the maneuver drive, the "canonical" explanation is this one:
http://traveller.wikia.com/wiki/Maneuver_Drive

While the decks of "belly lander" ships are oriented according to the ship's
axis of thrust, the decks of "tail sitter" ships are at a right angle to the
axis of thrust (well, the sentence seemed to make sense in German ...),
and this is about the only real difference.

 

[GypsyComet]

Another topic I'd like to discuss is the functionality of tail-landing starships. I understand what it means, that when the ship is landing on a surface, it effectively is sitting on it's 'tail' instead of 'belly' but how does this effect the people/cargo inside? What do tail-landing ships look like and how do they come in from vacuum to an atmosphere/gravity? I gather the Mercenary Cruiser from the core book is supposed to be a tail-sitter but the deckplans are kind of confusing as it seems that, in space the ship would always be flying 'up'.

Exactly the case. Sitting on the ground is really no different, as the decks are still parallel to the ground, but it takes off like a rocket instead of like a plane (or the rotorless helicopter feel that Star Wars grav gives).

As for entering atmosphere and landing, see if the web will cough up any footage of the Delta Clipper.

 

[Rikki Tikki Traveller]

My personal opinion is that Traveller doesn't have enough Tailsitter designs.

If the gravitics go out on most Traveller ships, people are going to be walking on the walls, not the floor. At least a tailsitter would allow minimal thrust without Inertial Dampers that would keep the ship from falling into a planet or star.

The Azhanti High Lightning design is the exception. A wonderful tailsitter design.

Starships seem to be built like airplanes, right or wrong. Gravitics must be VERY reliable.

 

[GypsyComet]

The Azhanti High Lightning design is the exception. A wonderful tailsitter design.

If you have a Lightning class Cruiser sitting on its tail, you've probably done something wrong...

Starships seem to be built like airplanes, right or wrong. Gravitics must be VERY reliable.

The Vilani have been using grav tech for five thousand years. By the standards on modern Earth, that's about what the wheel is to us.

Reliability is a pretty safe assumption.

 

[Alexander Cecil]

For MTU, I take lots of ideas I originally found in Fire, Fusion, and Steel and then modified.

All of my ships have three types of "thrusters". For maneuvering within atmosphere at reasonable pressures, the ship uses ducted jets combined with "contra-grav" technology to negate the pull of gravity. This let the ship fly carefully in-starport and even engage in some atmospheric maneuvers.

In upper atmosphere and when near other ships, the craft uses plasma rockets. These are needed to leave the atmosphere and for maneuvering in space combat.

When free and clear and moving in-system or gunning for the 100 diameter limit, my ships use fusion rockets. Since these fire off non-insignificant amounts of radiation, using them near other ships counts as firing a nuclear weapon when in Imperial Territory.

I enjoy this setup because it gives my players three sub-systems to worry about. More importantly, it gives me more to talk about when they are working with the maneuver systems.

"Yeah, your fusion rockets are getting stuck and not firing as precisely as you'd like, but repairing it is going to require a sealed environment and a rad-suit. You know . . . radiation protection . . . the stuff you traded out of the ship's locker at the last port. Good job."

This setup requires a bit more thought when I explain things, but the explanations are also more rich. I can get into detail about the sketchy quality of the launch catapult at a class C starport. I can have the fusion rocket's anti-rad casing get cracked, and the PCs have to deal with sealing it in a spacewalk. One vented jet can go down, requiring that the ship be towed around the starport by a grav-tug (at great expense, of course).

My method requires as much scientific hand waving as many others, but it gives me something to play with besides clearly reactionless (magic) thruster plates.

 

[Jeff Hopper]

Not Traveller, but a good website to help you define what is NOT canon engineering in Traveller is the Atomic Rocket Website. Link below.

http://www.projectrho.com/rocket/index.html

 

[AndrewW]

If the gravitics go out on most Traveller ships, people are going to be walking on the walls, not the floor. At least a tailsitter would allow minimal thrust without Inertial Dampers that would keep the ship from falling into a planet or star.

Who's to say the walls are walls? Without gravity or even in a microgravity environment there aren't walls/floors/ceilings. One could use any of the surfaces but unless your using magnetic boots or something it's hard to walk one could just float through pushing off walls and such.

 

[Infojunky]

Ok, this has got me thinking. Are Starships self starters? In the real world many large ships and airplanes need an external power source to turn on their power plants?

Some of this question is how efficient are batteries?

Or do most ships use smaller batteries and a smaller gen-set to bootstrap up to full power?

In general I like the concept of low efficiency plasma thrusters for planetary and station approach and high efficiency fusion drives for transit. Though the idea of also including low speed reaction-less drives has flitted through my universe as well....

I like a certain level of complexity in my systems design. This is more like how the real world works. In that while there might be some additional overhead in having multiple drives, the resulting installation with multiple drives is easier to contend with, especially in a error free environment.

Right now my biggest point is the lack of Life-support as an internal structure. I can design for it, in that in general the cost to support a person within the hull 250 Kcr per person. (which seems high until I figure the conversion rate to the Dollar (right now my internal assumption is 10cr to the dollar)). My real question of how much of this support cost is in the fixtures for the stateroom and how much is the machinery overhead.

 

[Woas]

Thank you all for the replies so far. The link you provided Jeff Hopper is great, i'm slowly reading through it. I'm still a little confused about tailsitters. Not that you all aren't providing great responses, it's just me being dense about the issue.

Regard tailsitters. Even our own space shuttles we use come back to earth as a belly sitter. Without the seemingly 'magical' anti-grav technology extended in Traveller "down" is in the direction of whatever propulsion system is pushing the ship. So okay, a Merc Cruiser wouldn't really even need antigrav plates since the people on board are standing parallel with the thrust of the ship. Where as in a bellylander, without the mystical force of antigravity to hold the crew, they would all be thrown to the 'back' of whatever room they were in, since that is technically 'down'.

But what about Merc Cruisers when they are trying to land? If you take a Merc Cruiser and aim it at planet, the crew inside would have to look 'up' to see the planet. Once they got near the planet what then? Turn thrust off, spin the ship so it is 'flying backwards' toward the planet and then have the planet's gravity pull the ship and then use thrusters to soften the landing and keep from just falling from the sky like a big golf ball?


Ach... my brain hurts.

 

[rust]

If you take a Merc Cruiser and aim it at planet, the crew inside would have to look 'up' to see the planet. Once they got near the planet what then? Turn thrust off, spin the ship so it is 'flying backwards' toward the planet and then have the planet's gravity pull the ship and then use thrusters to soften the landing and keep from just falling from the sky like a big golf ball?

Yep, exactly.

Just take a look at all those NASA designs of manned Moon Landers and
Mars Landers, almost all of them are "tail sitters".
The real world (and pre-contragrav) reason is that a "tail sitter" does not
need any kind of a runway, only a flat spot on the ground, and that it has
a significantly smaller "footprint" than a "belly lander".

 

[Rikki Tikki Traveller]

The US Space Shuttle is a belly lander because it lands UNPOWERED. It uses it's wings to control direction and speed, not it's engines. Thus it needs a LONG runway (it also flies like a brick btw).

 

[Woas]

Oooook. It's slowly getting clearer. Now, in a fictional world where spaceships are used frequently for trade, do you think a belly lander design would be more practical? With tailsitters being designed like a skyscraper, it seems like trying to get cargo in any deck other than the lowest one (where I would imagine the engines might be as well) would seem like a pain in the butt.

 

[AndrewW]

Oooook. It's slowly getting clearer. Now, in a fictional world where spaceships are used frequently for trade, do you think a belly lander design would be more practical? With tailsitters being designed like a skyscraper, it seems like trying to get cargo in any deck other than the lowest one (where I would imagine the engines might be as well) would seem like a pain in the butt.

Tailsitters do take up less space on the landing area though. With antigrav technology the higher up decks wouldn't really be any trouble. Not that all worlds would have this available.

 

[rust]

With tailsitters being designed like a skyscraper, it seems like trying to get cargo in any deck other than the lowest one (where I would imagine the engines might be as well) would seem like a pain in the butt.

Remember, you do not have to design a "tail sitter" like a skyscraper. It
could just as well be a flattened disk or any other configuration that is mo-
re wide than high, as long as it has the engines "below" the main body in-
stead of "at one end".

This one here is a "tail sitter", too:
http://www.orionspace.de/ww/de/pub/raumsektor_terra/risszeichnung.htm

 

[Woas]

With tailsitters being designed like a skyscraper, it seems like trying to get cargo in any deck other than the lowest one (where I would imagine the engines might be as well) would seem like a pain in the butt.

Remember, you do not have to design a "tail sitter" like a skyscraper. It
could just as well be a flattened disk or any other configuration that is mo-
re wide than high, as long as it has the engines "below" the main body in-
stead of "at one end".

This one here is a "tail sitter", too:
http://www.orionspace.de/ww/de/pub/raumsektor_terra/risszeichnung.htm

OOooooohhh! Like Slave-1, Boba Fett's ship! Interesting...

 

[GypsyComet]

But what about Merc Cruisers when they are trying to land? If you take a Merc Cruiser and aim it at planet, the crew inside would have to look 'up' to see the planet. Once they got near the planet what then? Turn thrust off, spin the ship so it is 'flying backwards' toward the planet and then have the planet's gravity pull the ship and then use thrusters to soften the landing and keep from just falling from the sky like a big golf ball?


Ach... my brain hurts.

No reason it should. You seem to have the basic idea.

Power landings are not a huge deal to ships that have a month worth of powered thrust available.

Again, the Delta Clipper is worth looking at. http://www.youtube.com/watch?v=wv9n9Casp1o

 

[Woas]

Switching gears back to powerplants and M/J drives for a second. For the most part it seems that the mechanism and actual 'engines' that power a Traveller spacecraft are located 'inside' the ship. Other than the obvious bonus of being able to work on an engine in need of repairs without going into the vacuum of space, could one save dTonnage on a ship by pushing some of the engines 'out'?

Having been doing a lot of custom deckplan/ship designing in preparation for my upcoming game I have been searching far and wide for inspiration. A lot of fictional spacecraft tend to have either circular 'thruster' exhaust that pokes a little bit out of the ship. Or they tend to have large, not really "steampunk" but lets called it "spacepunk" style engines that tend to have a lot of exposed engine parts. Does it have merit or something that should be left to 'eye candy'?

Secondly an another aspect of spacepunk is asymmetrical engines placement. Is that actually feasible? Quick and simple example would like, take a candle. Put all the engines at the 'top' where the wick is, but at a 90 degree angle so it would be on the side of the candle, not the flat top (like where the wick comes out of). Would a spacecraft like that just spin end over end in space? Engines have to be either down the center of gravity or make some sort of equal pattern?

Thanks again.

 

[GypsyComet]

It's all volume, whether its inside the ship or outside. The only drive system that gets outside is the solar sail in High Guard.

 

[rust]

If you wanted a space craft with very high agility, you could probably
build it with rotating engine pods attached to the hull, thus enabling it to
create thrust in every direction you want by turning the pods accordingly.
In my opinion this would make more sense for a space fighter than the
usual configuration with the engine at one end of the craft.

However, for normal ships a symmetrical arrangement of the engines is
most probably much better to handle, especially when moving through
an atmosphere to land or take off.