Ships coming in for a landing...

[hdan]

Just had a random thought:

When picturing traffic at a starport, does anyone else imagine grav-powered ships on final approach or takeoff behaving sort of like airships?

IMTU, ships carefully don't balance on their thrust vector like a helicopter or VTOL jet. Instead, as the anti-gravity drive powers up and gravitic mass effectively drops to zero, the buoyancy of the ship's hull in the local atmosphere takes over and the ship literally begins to float. (IMTU anti-gravity cancels "gravitic mass" but not "inertial mass".)

The grav lifters can be used a lot like a submarine's ballast tanks to control the effect. And much like a submarine, ships use their drives and attitude control thrusters for any rapid altitude changes.

Once ships float clear of the pad, they "nose up" and hit the m-drives to head for space. On airless worlds or worlds with too thin atmospheres, ships still cancel local gravity but use their attitude control thrusters to "push away" from the ground just like they would away from a space station.

One upshot of this model is that a landing ship can easily hover just above ground without causing any difficulties for people or vehicles below the ship. Older or less capable ships can be "lead around" the landing pad by ropes or more elaborate measures. Sure, they can also use their thrusters, but much like real ports where tugs bring ships into port, even low-tech worlds can find some sort of animal powered way to "tug" ships into their landing hangars. (Like mules working canals, I guess.)

I dunno, just some random thoughts for a Friday afternoon.

 

[rust]

This is exactly how I handled it in those of my settings
where gravitics existed.

 

[DFW]

IMU ships grav drives create a gravity well in whatever direction and orientation they want to go in.
So, they lower themselves down and up. From the "pad" they float up until clear of traffic then reorient the grav well to in front of the ship and generally go nose up to orbit.

Unless of course the local grav is equal to or greater than the drive rating. In which case you must have wings (think space shuttle) to take off and land.

 

[apoc527]

I've always wondered: what kind of threat do high winds present to a typical m-drive using ship? Pilot checks? Is it possible to crash even?

 

[DFW]

I've always wondered: what kind of threat do high winds present to a typical m-drive using ship? Pilot checks? Is it possible to crash even?

Depends on wind speed, direction and altitude that ship is at.

 

[apoc527]

Flying through Hurricane Irene?

 

[DFW]

Flying through Hurricane Irene?

If a grav only ship with a higher M-drive rating than the planets gravity(no wings), not a problem. With an "airframe" (wings) ship, wouldn't want to try it unless Flyer-2 or better. Difficult task

 

[Reynard]

I've always wondered: what kind of threat do high winds present to a typical m-drive using ship? Pilot checks? Is it possible to crash even?

Atmospheric conditions do affect a space/starcraft.

Reading several Traveller sources the Maneuver Drive is a combination contra-grav lifter system and a reactionless 'thruster' system. Non-space/starcraft such as the air raft use the same systems. The CG system function is to neutralize gravity of the planet but has no ability to provide any vector movement. Standard thruster plates provide push in any direction. If we consiter one older source material, the plate's thrust is reduced as you aim away from aft thrust but it still allows for vertical takeoff and landings though landing and launching like a typical rocket would be faster.

Even with these systems, they don't magically maneuver a ship in an atmosphere. That's why a distributed hull, at best, will make an assisted crash landing in the best of conditions and never fly again and a standard configuation is akin to a very advanced NASA space shuttle. Streamlined craft are specifically ment to enter and fly in an atmosphere but are subject to the weather as any aircraft. The CG system allows the ship to 'float' in place but winds would push it around as if it were a hot air balloon. Thrusters allow movement but it's the pilot's skill that actually fly the craft from grav belts to starships.

 

[rust]

Flying through Hurricane Irene?

It would certainly be a very unpleasant experience. A big ship,
with a high mass and therefore a high inertia, would probably
have less problems, but a small ship and especially a small
craft could well be in serious danger. However, I doubt that it
would crash, although the buffeting [I hope that word exists]
could well injure the crew and damage the craft - sudden vec-
tor changes caused by 300 km/h winds would surely hurt.

 

[phavoc]

I've always had it where ships would move slowly through the traffic pattern. Different starports are going to have different rules. Large ships will be relegated to the outskirts to minimize risk. Smaller ships would maneuver and land in designated landing areas and/or built-in landing pads. For liftoff they would slowly lift up, then maneuver to the 'lauch area' and then engage their drives.

Larger starports are going to be more interested in minimizing risk and keeping everything flowing smoothly. A 10,000Dton freighter whose grav drives failed when coming in for a landing is gonna ruin a lot of people's days - especially if there are people or structures below. But smaller starports, think more like D and below, well, they are going to be much less rigid with things. Ships taking off are more or less going to launch as they will (think the Millenium Falcon departing Mos Eisley... it lifted off the deck, cleared the docking bay, then pointed its nose and hit full thrust. A busier starport probably would never allow that except in emergencies, and then limited to official and military craft only.

As for weather, well, even a small scoutship is going to weigh a lot. A ship under anti-grav is not going to act like a blimp. It's going to take a LOT of wind to move something like that. Anti-grav doesn't reduce mass, just weight.

Does anyone recall what a scout would weigh? I know SJG used to keep Dtons and weight separate in all their calculations, but they were really the only version of Traveller that I recall that did that.

 

[rust]

Does anyone recall what a scout would weigh? I know SJG used to keep Dtons and weight separate in all their calculations, but they were really the only version of Traveller that I recall that did that.

In GURPS Traveller 346 tons (loaded mass), in Traveller
New Era 684 tons (loaded mass).

 

[DFW]

As for weather, well, even a small scoutship is going to weigh a lot. A ship under anti-grav is not going to act like a blimp. It's going to take a LOT of wind to move something like that. Anti-grav doesn't reduce mass, just weight.

Yep, that's why prop planes that mass a LOT less and have lifting surfaces to worry about can fly through the worst hurricanes. When the wind is blowing in a known direction (like inside a hurricane) you can fly through them. Also why airliners an fly through winds as high as 300kph when you know the direction.

 

[Rick]

Has anyone looked at using an airport's air traffic control system as a basis for a spaceports air/orbit traffic control? There would probably only be a few approach lanes to the landing areas, but the incoming traffic would be stacked according to their capabilities or landing patterns.

 

[rust]

Has anyone looked at using an airport's air traffic control system as a basis for a spaceports air/orbit traffic control?

This is how it is described in GURPS Traveller Far Trader, the
system there is basically the current air traffic control system,
only expanded to cover the space out to the 100D line.

 

[AndrewW]

There is a ship designed for traffic control. The Space Control Router, Shepherd-Class. It's located in Supplement 2: Traders & Gunboats (page 8).

 

[DFW]

Has anyone looked at using an airport's air traffic control system as a basis for a spaceports air/orbit traffic control? There would probably only be a few approach lanes to the landing areas, but the incoming traffic would be stacked according to their capabilities or landing patterns.

You would have 2 basic classes. Those that land like an aircraft and those that can VTOL. So, you'd have runway traffic and what is the equivalent of helo traffic.

Also, our TL 6/7 aircraft (commercial) only see other craft if they are using transponders. Not so with high tech spacecraft. Expect control & routing to be extremely automated. You aren't going to be in voice contact unless something terrible is happening.

 

[AndrewW]

Also, our TL 6/7 aircraft (commercial) only see other craft if they are using transponders.

That could change if NexGen ever gets put in place.

 

[DFW]

Also, our TL 6/7 aircraft (commercial) only see other craft if they are using transponders.

That could change if NexGen ever gets put in place.

Really? I thought it still used transponders.

 

[Reynard]

>You aren't going to be in voice contact unless something terrible is happening.<

"Uuuh.. Ship 196-T?"

"Oh crap..."

 

[Reynard]

>As for weather, well, even a small scoutship is going to weigh a lot. A ship under anti-grav is not going to act like a blimp. It's going to take a LOT of wind to move something like that. Anti-grav doesn't reduce mass, just weight.<

A ship still has mass just as atmosphere has energy. Energy applied to a mass produces acceleration. A streamlined spacecraft operates much better in those conditions even if only to maintain position.

Bad weather grounds aircraft and makes ships avoid docking and that includes some pretty massive vessels. The space shuttle is a big mass yet it never takes off or lands in bad weather except in emergencies. It can be done but it can be an expensive blunder.

I can see spaceships and starships force to maintain orbit or be directed to other downports. One way to introduce an adventure. Then there's the thrill of making that forced or overly important landing.