Agility and the CT manuever drive

[Spankstinator]

Hello,

I did a search on manuever drives in the forum's but could not find a discussion that answered this question.

What sorts of evasive manuevers would be possible with a ship's boat in the atmosphere of a planet?

Would the boat be able to use its reactionless manuever drive to direct 100% of its "thrust" (I know it's not really thrust) say perpendicular to its vector and still not loose its forward momentum (except for atmospheric friction)?

For example, what if someone shoots a conventional (TL 7 or 8) rocket powered missile at a ship's boat using it's manuever drive to go straight up from the planet.

Because of counter grav, the pilot of the boat could "sidestep" the missile fairly simply and still maintain upward momentum right?

Similarly, wouldn't it be really hard for a jet fighter to engage a ship's boat in a dogfight for the same sorts of reasons? The ship's boat would be juking all over the place using flying saucer type manuevers, while the airplane would be limited to turning.

Thanks,
-The Spankstinator

 

[robject]

Depends on what the referee allows.



I think gravitic craft with maneuver drives are much more maneuverable than conventional aircraft, and therefore are not under much threat at all from TL7 missiles or aircraft.

 

[Spankstinator]

Thanks Robject,

I was just imagining the extraction mission in your Working Passage forum, visualizing how a pilot might actually fly such a mission (or even myself if it were a computer sim game with actual point-of-view piloting rather than text-based narrative).

My confusion stems from the fact that all official Traveller pics and deckplans show rocket-like exhaust ports at the aft end of the ships. This implies that the ships must actually turn to focus their "thrust" along another vector rather than "slip" around. Since this turning would take a finite amount of time, it seems that Traveller ships can't just juke around like flying saucers.

But the m-drive is described as "reactionless"; so why the exhaust ports (besides the fact that they look cool) if there is no thrust?

Of course, I won't bog down Working Passage with all these unnecessary details.

Thanks,
-The Spankstinator

 

[far-trader]

Greetings Spankstinator,

The answers to your questions will depend on how close you or your ref want to stick to canon and just where your canon is from. Some of my thoughts for what they're worth...

The common deep space maneuver is to accelerate at full power for the first half the journey, conduct a midpoint turn-over, and then decelerate at full power for the last half of the journey. Orbital runs seem to presume that the planetary gravity is ignored (anti-gravity field being part of the maneuver drive in my opinion) and ships accelerate at full power. That goes back to CT (LBB 2).

In fact I don't believe that CT (LBB 2) maneuver drives were entirely reactionless based on the fuel use. I have interpreted the fuel requirement of the power plant as "allows routine operation and maneuver for four weeks" to be the amount used to maintain the jump bubble (the routine part) or as reaction mass (the maneuver part). The actual fuel to run the lights and such is minimal and inconsequential in most circumstances.

So in my opinion even a 1G Maneuver drive will have no problem outrunning most atmospheric craft and missiles, they will however not be highly agile. I don't allow space craft agility to work at planetary range. Think more like jet helicopter or VTOL jet plane for performance. Very quick in straight and level with the ability to go very slow and hover but subject to wind loads when doing it.

FWIW later editions of the rules (where maneuver is called reactionless) describe the "exhaust" as waste heat dump from radiators. The radiators are usually mounted aft and the heat plumes resemble exhaust in certain spectra. Those rules still limit your thrust to one direction since the plates have an orientation of most efficient thrust (though they do have some thrust off axis, negligible for most cases). If you're interested the numbers are: 90deg off axis is 25% thrust while reverse thrust is 10%. The rules allowed overdriving the maneuver plates to 400% for short periods, thus allowing standard 1G ships like the Beowulf with aft pointing thrusters and perpendicular decks to hover in a deck down attitude while landing and taking off. A solution that caused more problems than it fixed imo.

 

[mike wightman]

IMHO it isn't the maneuver drive that gives the ship's boat the main advantage, it's the acceleration compensators.
In CT these negate the effects of high maneuver and lateral G forces - thus the boat can pull off some pretty amazing dogfighting maneuvers that a TL8- fighter just couldn't match without killing the pilot.

 

[parmasson]

Just my Cr 2

The way we play it is that the “thrust” is directed aft and the grav suspension causes it to maneuver like a lighter than air vessel. We play them as floating in the air just like a blimp or dirigible.

If the small vessel has “wings” like the fighter or 95 ton shuttle then they can maneuver like regular aircraft.

 

[Andrew Boulton]

Most small craft don't have much in the way of control surfaces, and they're generally not designed for this kind of thing. They probably steer like a cow. MT limits their atmospheric speed to 1000km/h (~Mach 1). A TL 7+ jet fighter or SAM would ruin your day.

 

[robject]

I'm with Sigg, and I understand Parmasson's post.

Here's what I think about the launch.

I think it has retractable wings. The thruster plates' axis is more or less pointing aft, probably like far-trader's last paragraph. It has CG lifters that would allow it to attain orbit (in 7 hours' time, from the ground on Ruie) even if the maneuver drive was inoperable. And it has acceleration compensators. Finally, TL12 ceramic coils can store excess heat for convenient dumping at a later date; therefore most of the heat issues are gone.

So: you can shoot to the surface like a bullet. You can have aerodynamic effects (if you like) without pilot or passenger strain. You can decelerate and hover. You can juke around slightly -- enough to sidestep TL7 missiles, even at close range.

I haven't really thought it all through, either.

 

[Andrew Boulton]

It's not that simple. You need proper control surfaces for high-performance atmospheric manoeuvering and supersonic speeds, which most small craft don't have. A good pilot might manage to dodge a missile, but don't count on it.

 

[SanDragon]

In other words, an airframe configuration?

 

[Andrew Boulton]

Exactly. Some small craft are AF - shuttles, for example - and they'd be okay in a dogfight.

 

[Spankstinator]

Andrew,

I am not an aerospace engineer so please correct my ignorance. I am new here and I am not trying to be sarcastic or offensive. This is a noob request for clarification.

What is superior about an airframe configured craft subject to gravity that uses aerodynamic drag to change its pitch, yaw and roll compared to a streamlined ship's boat with thrusters (the reactionless equivalent, of course) that can change it's pitch, yaw, and roll at an equivalent (or why not superior?) rate and can also control how it is subject to gravity due to varying its antigrav intensity?

-The Spankstinator

 

[Fritz_Brown]

This is one of those gearhead things, partly, Spank. If you look too hard at things like contragrav and reactionless thrusters that point in all directions as desired, it just gets a bit over the SoD[1] threshold.

There's also the bit about how agility is measured, and very few craft (with the thrusters) have an agility anywhere near 6G, and none at 9G - where the F16 is. So, how do you account for that? It must be because [insert gearhead explanation here].

Now, if you assume that the thrusters are pointed aft, but the ship can flip around at a 6G rate, then you get a fairly manueverable craft, but still not where modern aircraft are. If you add aerodynamic surfaces, you get better agility, but you would have to assume the inertial dampeners could only handle the first 6Gs (or whatever the ship is rated). So your crew better be holding on to something and sitting down.

Personally, IMTU, there will no longer be reactionless thrusters. I just can't give up my grounding in Newtonian physics.

[1] SoD - Suspension of Disbelief

 

[Spankstinator]

Thanks Fritz88 and everyone else.

I am very interested in "how things might work." This is my first discussion here and I enjoy the responses and thinking about their implications.

I would imagine that F-16 pilots and SAM missile battery operators if faced with Traveler tech would stink at first. But people could eventually be able to devise tactics to deal with the new situations optimally, maximizing their effectiveness.

Can you imagine the "Project Blue Book" tactics for a F-16 engaging a flying saucer?

-The Spankstinator

 

[Rossoneill]

I just use the T20 Agility rules for agility
If you have extra power for agility you have agility .
Agility =AC+
If you have a good pilot who makes his evasion roll he has added AC .
Of course YMMV

 

[parmasson]

By Rossthree

I just use the T20 Agility rules for agility...

Hmmmm "T20" eh? That new-fangled citypated Traveller. (Said with a suspicious glance)

by Spankstinator

Can you imagine the "Project Blue Book" tactics for a F-16 engaging a flying saucer?

I am thinking that the x-ray lasers would give them quite a shock and anything with a stealth package would just disappear form the screens.

 

[robject]

Yeah. Well, really, Suspension of Disbelief doesn't exist in my book. I might be gullible. I've seen things in real life that used to be science fiction, and I bet there are things down the road that will surprise us. I've heard SoD used as a reason for things before [radiator fins on starships for example], but for some it could be a gearhead and/or crunchy bits issue at the core.

 

[Fritz_Brown]

Actually, robject, by your statement, SoD IS your book. As mentioned elsewhere, SciFi works well when SoD only has to operate on a few things: Traveller's is jump, gravitics, and reactionless thrusters. (And trade systems for some like Far Trader!)

For gearheads, that's sometimes too many in one pot. That's why the IMTU statement. (BTW, I'm giving up inertial compensators, too - just too much handwavium in the gravitics to accept that AND contragrav AND artificial grav AND anti-grav.) YMMV

 

[mike wightman]

You could mitigate SoD by combining jump drive, grav plates, nul grav modules, maneuver drives, and acceleration compensators all into one grav based technology.

 

[ditzie]

Hi Mister Sigg!

Yes yes um gravvie-wavvie is all the same. I used to say "no" but Unkie Hengie an the nice sparkly-warkley lab techs they let me play with with the hololab puter an an an it made some sparks an an smoke an stuff then they had to replace it.

But before it did it it it showed me grav is is it goes inwards an an then it pulls. An you pull on people an an they pull back so they don't float. But they're just flipped over an an an they're really they're just the same. So it goes outwards then then it pushes. An you just push on the planet an it pushes back because it's supposed to.

An an an the really really neat part is if you push on space it'll push back, too. An just like Newwwton said, so so it's a reaction-waction drivey wive sort of but not like throwing things, more like pushing and pulling things. But the puter didn't tell me where all the hydro-wydrogen goes before it went boom 'cause it's too much for fusion so I think there's funny things there an an I want to ask him about it but he just stares an Unkie says he doesn't exist. But it's it's sometimes you call it a module and sometimes a plate an you can say it it it's a compensator-wator but they have the same stuff.

An an an an you can um just hook two up so so that so that one pushes an an an the other it pushes just the same but the other way. So then you don't feel anything at at all. The ship I mean. Oh an an people too if you want. Because I like wavey-wavey cancewation too an an it looks like sort of like that but different.

But but Mister Sigg the jump drive is different, an an an an I told him an he says I'm right but not to tell you or Unkie about thaaat.