vectored thrust

[abomination]

I've been reworking the 440 ton corsair design. Is there any reason why I can't put an additional set of thruster plates on the underside of the hull as "landing gear"?

The ship has 3g maneuver, however the plate at the bottom of the hull can produce 1g which while in use reduces the main thrust to 2g.

Thoughts?

 

[samuelvss]

What system are you using?

 

[abomination]

What system are you using?

MT

 

[far-trader]

Depends on how canon and by-the-rules legal you want to be

Thrust in Traveller, MT specifically, if you take SOM (Starship Operator's Manual) as a given, is generally directed thrust. That is (most if not all) your thrust is in one direction. So if you put a 1G plate on your belly it won't add to the thrust of the 2G plates on the aft.

However...

...a few things might work.

First, I'm pretty sure MT included the idea of lifters, which negate some 99% of the local gravity. Not quite the same as your 1G of thrust but effectively very close to it.

Second, you could make it a tail lander and keep all your thrust in the aft.

Third, the same directed thrust rules in SOM allow overpowering the thrust for short periods to permit landing. From memory a 1G thrust ship (aft) can overpower by 4x to create 1G thrust down for long enough to land. Normally the off-axis thrust is 25% at 90 degrees (so your 3G ship would have 3/4G thrust down available all the time anyway, which is almost your 1G. You could easily use it to counter the gravity of a size 6 or smaller world for as long as your fuel holds out.

Fourth you could get creative and make the thrusters true vectored thrust by putting them on gimbles and just pointing them the way you want. The problem with that is there are no rules to cover it so you have to make them up.

...but.

There's always a but. In this case it looks like your looking for a way around the rules that say an unstreamlined ship can't land (at least not in atmosphere). If that is your intention you'll have a lot more rules to work around anyway so just make it so and ignore the rules that would be in the way. Nobody will break down your door and take your Traveller game away from you...

...they may however grief you to no end here on the forum

 

[HG_B]

Depends on how canon and by-the-rules legal you want to be

Thrust in Traveller, MT specifically, if you take SOM (Starship Operator's Manual) as a given, is generally directed thrust.

Yes, I believe that other than SOM, MT didn't rule that thrust wasn't omni-directional. So, if you play without that supplement, I don't think there is a problem.

 

[far-trader]

Yes, I believe that other than SOM, MT didn't rule that thrust wasn't omni-directional.

I'm pretty sure MT is still directed thrust even without the SOM elaboration. Isn't there a description complete with a nice diagram of the typical normal space trip of full thrust to midpoint - TURN ABOUT ON AXIS - and full thrust to stop?

In fact, without the SOM elaboration providing off-axis thrust to land a horizontal deck in alignment with local gravity the implication is (and maybe I'm misremembering the whole appearance of "lifters") that the maneuver drive is what keeps you flying in a gravity well. Just like in CT where you needed more thrust than local gravity to be able to land.

 

[HG_B]

I'm pretty sure MT is still directed thrust even without the SOM elaboration. Isn't there a description complete with a nice diagram of the typical normal space trip of full thrust to midpoint - TURN ABOUT ON AXIS - and full thrust to stop?

In fact, without the SOM elaboration providing off-axis thrust to land a horizontal deck in alignment with local gravity the implication is (and maybe I'm misremembering the whole appearance of "lifters") that the maneuver drive is what keeps you flying in a gravity well. Just like in CT where you needed more thrust than local gravity to be able to land.

You may be correct. I can' remember the exact wording. But, that may be the reason SOM came up with 90 degree figures.

 

[aramis]

First, I'm pretty sure MT included the idea of lifters, which negate some 99% of the local gravity. Not quite the same as your 1G of thrust but effectively very close to it.

No, it doesn't. Those didn't appear until TNE.

 

[abomination]

Depends on how canon and by-the-rules legal you want to be

Thrust in Traveller, MT specifically, if you take SOM (Starship Operator's Manual) as a given, is generally directed thrust. That is (most if not all) your thrust is in one direction. So if you put a 1G plate on your belly it won't add to the thrust of the 2G plates on the aft.

I was more thinking of having additional plates on the belly as well as the main 3g plates aft. When landing, taking off & generally flying around the planet up to 1/3 of the power is diverted from the main rear plates to the belly plate.

However...

...a few things might work.

...Second, you could make it a tail lander and keep all your thrust in the aft.

Yeah, but that just feels messy

Third, the same directed thrust rules in SOM allow overpowering the thrust for short periods to permit landing. From memory a 1G thrust ship (aft) can overpower by 4x to create 1G thrust down for long enough to land. Normally the off-axis thrust is 25% at 90 degrees (so your 3G ship would have 3/4G thrust down available all the time anyway, which is almost your 1G. You could easily use it to counter the gravity of a size 6 or smaller world for as long as your fuel holds out.

Having to routinely over run the engines seems like bad design to me.

Fourth you could get creative and make the thrusters true vectored thrust by putting them on gimbles and just pointing them the way you want. The problem with that is there are no rules to cover it so you have to make them up.

I thought about that, but they seemed waaay to big. Maybe if I went for lots of small plates, but that is nearly the same thing as having an extra smaller plate on the belly.

...but.

There's always a but. In this case it looks like your looking for a way around the rules that say an unstreamlined ship can't land (at least not in atmosphere). If that is your intention you'll have a lot more rules to work around anyway so just make it so and ignore the rules that would be in the way. Nobody will break down your door and take your Traveller game away from you...

...they may however grief you to no end here on the forum

It's not that, I've paid for streamlining, because I can't see why anyone would build a corsair that couldn't do skimming / wilderness refueling. It's mostly I hate the idea of a ship landing backwards before toppling forwards at the last minute. It's just not ...... how Han Solo would do it dammit!

 

[far-trader]

I was more thinking of having additional plates on the belly as well as the main 3g plates aft. When landing, taking off & generally flying around the planet up to 1/3 of the power is diverted from the main rear plates to the belly plate.

Ahh. Yeah that should work fine, imo, fwiw

As far as that goes, if you have the room, add a short operation power plant for it. So you have the main drives and power plant rated at 3G and 3P that can operate for weeks at a time, then have your landing drives and power plant rated at 1G and 1P that usually operate only for minutes or hours while landing or otherwise close to a gravity well. Heck, even make the landing cycle drive battery operated for stealthy approaches

 

[atpollard]

Viewing the ship as a brick ‘flying’ level, the 3G of thrust directed straight back will produce a 3G acceleration forward while the craft falls vertically at 1G (or whatever local gravity is).

Standing the ship on its tail will allow you to accelerate upward at about 2G (3G – 1G local gravity).

Pointing the nose up about 30 degrees, will provide a 1G of vertical component and 2G horizontal component to the thrust vector (without vectoring the thrust relative to the axis of the ship). On a vacuum world, this position would allow you to ‘fly’ at a constant altitude while accelerating at 2G horizontally.

On a world with an atmosphere, wind drag will slow the forward movement of the ship creating a ‘top speed’ for your craft, but flying at an angle will also convert some of the drag into lift. Adjusting the angle of the ship and the thrust should allow even a brick to fly … to climb, descend, accelerate and slow down. The poor aerodynamics of the ship will require more thrust than an aerodynamic shape, but at 3G you have power to spare. The high drag and low lift will require either a very steep angle of flight (approaching a tail lander) or a high landing speed (like the Space Shuttle).

Given your high drag and high thrust, the ship seems a good candidate for a flared landing (like a hang glider). You approach the landing spot skimming the surface at a fast speed and low angle (say nose up 20 degrees from level) and suddenly point the nose sharply upward (say 60 degrees from level) causing the ship to stall (horizontal speed falls to zero and lift falls to zero) causing the ship to hang still in the air for a moment before dropping to the ground like a stone. Voila, you just landed.

Even a small vectored thrust (and certainly 3/4 G vertical) could easily convert that to a gentler short runway or vertical landing.

FTMMV (FreeTraders Mileage May Vary)
[just kidding]

 

[HG_B]

The long and short of it is, streamlined and unstreamlined ships will land & take off on vacuum & trace worlds the same way. Whatever way that is...