Rule for grav vehicles?

[sideranautae]

Is there any MGT rule regarding how Grav cars (air/rafts) and the like work as far as altitude limitations, deep space operation, etc?

 

[sideranautae]

I didn't think I saw MGT rules for this.

More to create and write...

 

[dmccoy1693]

Overtly written rules: to the best of my knowledge, none. However. I would say it is safe to infer that a grav vehicle can operate in the vacuum of space up to an altitude as high as you want to go since it is the same kind of drive system as space craft, only alot smaller. Plus there is the option for vacuum crew protection as a vehicle option. IMO, the only limit to a grav vehicle's operation is fuel, environmental protection, and not going underwater since no depth limitation is listed.

 

[phavoc]

Can't say where I got this (as I don't recall) but grav vehicles (like air raft, G Carrier, etc) can only operate near a planet or moon. So they have sufficient capabilities to get to low orbit only. Ships designed to travel between planets have a different type of grav drive and they don't have that limit.

That's how I've always played Traveller.

 

[sideranautae]

Overtly written rules: to the best of my knowledge, none. However. I would say it is safe to infer that a grav vehicle can operate in the vacuum of space up to an altitude as high as you want to go since it is the same kind of drive system as space craft, only alot smaller. Plus there is the option for vacuum crew protection as a vehicle option. IMO, the only limit to a grav vehicle's operation is fuel, environmental protection, and not going underwater since no depth limitation is listed.

Hmm. I thought that the minimum size for a Space Grav drive was listed in the HG as .5 Tons. But you're right. The TL 14 Spacesuit Thruster pack says that it uses the same grav drive type as space ships. That one gives 1/10 G thrust using Spacecraft fuel (L-hyd). I can spec its volume vs. the size of a person to create specs for G-rating of vehicles. Also, that tells me that at TL 14 there is man portable fusion reactors.

Thanks!

 

[sideranautae]

Can't say where I got this (as I don't recall) but grav vehicles (like air raft, G Carrier, etc) can only operate near a planet or moon. So they have sufficient capabilities to get to low orbit only. Ships designed to travel between planets have a different type of grav drive and they don't have that limit.

That's how I've always played Traveller.

I remember something about that in MT design rules. I distinctly remember the Low Orbit part you mention.

 

[Tom Kalbfus]

Is there any MGT rule regarding how Grav cars (air/rafts) and the like work as far as altitude limitations, deep space operation, etc?

I have an idea. Antigravity vehicles don't negate Newton's laws of motion, that is for every action there is an equal and opposite reaction. So lets say a grav vehicle exerts a negative gravitational force, that is it pushes all matter away from it. It pushes on the ground and it pushes on the air, Gravity also obeys the inverse square law, so if for instance the grav vehicle pushes away all matter with 1g of force at 1 meter, then at 2 meters radius it pushes away at 1/4 g of force, so on a 1 g planet, the grav vehicle hovers at 1 meter above the ground and no more if there is no atmosphere. If you increase the gravitational repulsion, it pushes away the air surrounding the vehicle, if I pushes away enough air, it creates a virtual balloon of lower air density around it and buoyancy causes the grav vehicle to rise. Now one has to remember that the gravity of a planet diminishes more slowly with distance than does the gravity field of a grav vehicle. Making a small antigrav field is one thing, but producing one that equals the magnitude of the gravity of a planet is something entirely different, and if you could do that, the planet would blow up! I don't think any of the grav vehicles on the equipment come close to this however. What they can do is push off the ground in vacuum worlds and rise to an altitude where the antigravity equals thje gravity at the surface of the planet, and that would be the maximum altitude. On a planet with an atmosphere the maximum is probably somewhere near the top of the atmosphere, about the maximum altitudes achievable by balloon flights.

 

[sideranautae]

Is there any MGT rule regarding how Grav cars (air/rafts) and the like work as far as altitude limitations, deep space operation, etc?

I have an idea. Antigravity vehicles don't negate Newton's laws of motion, that is for every action there is an equal and opposite reaction.

I already took care of that in my rules long ago. The Grav drives create a 2D grav well that surrounds the ship and causes it to free fall in whatever direction and violates no known 'laws'.

I too disliked violating fundamental physical laws. That's why I eschewed MT's reactionless Plate drives...

 

[atpollard]

I already took care of that in my rules long ago. The Grav drives create a 2D grav well that surrounds the ship and causes it to free fall in whatever direction and violates no known 'laws'.

I too disliked violating fundamental physical laws. That's why I eschewed MT's reactionless Plate drives...

So if. I am sitting in my grav car, waiting for a traffic light to change, am I in danger of having my coffee float out of the cup because the car, the coffee and me all experience weightlessness from the pull of the 2D gravity well above us?

 

[dragoner]

Can't say where I got this (as I don't recall) but grav vehicles (like air raft, G Carrier, etc) can only operate near a planet or moon. So they have sufficient capabilities to get to low orbit only. Ships designed to travel between planets have a different type of grav drive and they don't have that limit.

That's how I've always played Traveller.

I use a sort of "negative mass emulation" http://en.wikipedia.org/wiki/Negative_mass so yes, it has that same effect, but there is the question of how grav plates and thrusters work where there is no mass to work off of.

 

[sideranautae]

So if. I am sitting in my grav car, waiting for a traffic light to change, am I in danger of having my coffee float out of the cup because the car, the coffee and me all experience weightlessness from the pull of the 2D gravity well above us?

Yep. Without compensatory internal g-field. All early (pre-TL 11) grav vehicles had that as a "feature". On the plus side, you never feel acceleration.

In a grav belt you are always in free fall. (IMTU)

 

[Reynard]

Looking over various editions from CT to MgT, all state that grav vehicles are limited to planetary orbit. I can say it seems obvious that vehicle power and drive systems are very inefficient compared to more massive scaled space units. This is the cost for having such miniaturization.

It used to be noted spaceships and planetary grav vehicles both utilized grav lifters for maneuvering within the boundaries of a planetary body. What gave spaceships extra-planetary capability is the maneuver drive allowing much greater gravitic 'push' against vastly reduced gravity wells in deep space. I think this is also why you don't see examples of grav vehicles travelling between starships in deep space.

Just so I don't insert foot firmly in mouth I checked drones in both the Core and High Guard. Drones with anti-grav operate in grav wells while those meant to operate in space are either crawlers, equipped with thrusters or are drone ships.

 

[sideranautae]

Looking over various editions from CT to MgT, all state that grav vehicles are limited to planetary orbit.

I know that before MGT it was thus. But, that changed with MGT. See MGT reference I found above for Man sized Deep space grav propulsion. Also, MGT doesn't state that vehicle sized AG is limited to orbit.

 

[Reynard]

Check the air/raft description which is the icon of planetary grav vehicles. Once again, Mongoose simplifies Traveller and doesn't include all the minutia from the other canon editions. The Air/raft descriptor has always mentioned no space flight and other vehicles have followed suit in various locations.

Probably in the book I don't have but I'd like to know about the Man Sized Deep Space Thingie. What is the source and how do they explain its function and purpose? Even non-ship space accessible drones don't use anti-grav.

 

[sideranautae]

Check the air/raft description which is the icon of planetary grav vehicles.

I did (for Mgt). It doesn't state that it is LIMITED to only orbit. That coupled with the fact that there is a vehicle sized deep space vehicle that uses grav as propulsion causes a problem. :wink:

Plus, "orbit" isn't an altitude. If on a flat, airless world, "orbit" can be as low as a kilometer off the ground. It needs an actual rule that works for all planets.

Could need errata. I wish that MGT would do that when needed.

 

[Reynard]

"...can even reach orbit...". That simple.

"Plus, "orbit" isn't an altitude. If on a flat, airless world, "orbit" can be as low as a kilometer off the ground. It needs an actual rule that works for all planets."

Oh don't do that. An orbit is the point a object's energy allows it to move sideways to the central gravity source without falling toward or flying away. It IS altitude. You'll often hear how a vehicle needs tremendous energy to break free of Earth's gravity while still able to achieve orbit.

Traveller grav vehicles and their power/drive sources are too small, too inefficient to use a world's gravity to break free. Mongoose didn't go into the minutia (THANK YOU) and just says keep it simple and don't do it.

 

[sideranautae]

"

Oh don't do that. An orbit is the point a object's energy allows it to move sideways to the central gravity source without falling toward or flying away. It IS altitude. .

:?: :?: :?: :?: No. There is no specific altitude required for an orbit. You can learn more about it here: http://en.wikipedia.org/wiki/Orbit

The canon ball example in particular will help you visualize it. On an AIRLESS body as long as the object moves tangentially, it falls toward the central body. However, it has enough tangential velocity to miss the orbited object, and will continue falling indefinitely. This can occur at ANY altitude (as long as you clear ground protuberances) on an airless body.

 

[Reynard]

First off, where did I state a specific altitude? By the way, thank you for repeating everything I said in my last post. Now, you need to not only read but understand what was said by both of us. I don't have the space to teach a course. Simply, there is a wonderful formula out there showing gravity pulling in you in while your energy tries to send you away. When the energy is vectored properly you achieve an orbit, a circular motion about the point at a certain distance (altitude). As with any mathematical equation, whatever happens to one side has an equal effect on the other. When the opposing energies change, the vector velocity and/or the altitude changes. Altitude is variable.

God help us if Mongoose had to explain every rule in the book!

 

[sideranautae]

An orbit is the point a object's energy allows it to move sideways to the central gravity source without falling toward or flying away. It IS altitude

In argument AGAINST me stating that a rule defining the altitude of "orbit" vis-a-vis grav vehicles is needed.

So, once again, what is your proposed rule in MGT for the SPECIFIC ALTITUDE limit for grav vehicles based on planetary size? Since MGT has vehicles using grav drives in deep space currently as opposed to limiting them FROM deep space operations. You are proposing a Dimensionless quantity (orbit) as the rule. But, that doesn't work as a game rule as that can mean from 10 meters to tens of thousands of meters in ALTITUDE on the same planet.

 

[Reynard]

Mongoose and all the other editions kept it simple, very simple. Well, maybe not MegaTraveller - the Minutia Edition. Grav vehicles can reach orbit meaning they do not leave the planet beyond what most ships determine to be a simplistic, vague boundary. Air/rafts do not fly to the moon or Jupiter. They are simply planetary vessels. Never in the history has there been grav tanks battling starships.