Getting a 1g ship off a >1g world

[Zenguy]

So the party has been roving the sector in a Far Trader pulling whatever cargo and jobs they can find to make their way. In the process they have been on and off worlds of all sizes and atmospheres.

Now their ship is only capable of 1g acceleration. So ...
How did they get off all those worlds that have greater than 1g surface gravity? o:

And following on from that: How can I let them continue doing so without having to:
a) fudge over what has happened in the past,
b) restrict them to worlds of 1g or less,
c) get them to hire tugs for jobs on >1g planets,
d) upgrade their ship, and/or
e) change the laws of physics?

I'm rather hoping the answer is something like: 1g acceleration applies once in space, but the ship has additional grunt when it comes to getting off-planet.

 

[mmbutter]

Err, acceleration greater than local gravity is only required when you're trying to brute force a launch directly up. Aerodynamic lift can be used to launch when there is not enough power to go straight up.

Physics allows this; after all, most commercial airplanes on Earth do not have more than 1g of acceleration yet they are able to leave the ground every day.

 

[far-trader]

I'm rather hoping the answer is something like: 1g acceleration applies once in space, but the ship has additional grunt when it comes to getting off-planet.

It's one of the possible answers

It depends a lot of which set of rules you're playing and how close to them you want to stick.

CT did count local gravity.

MegaT iirc introduced the concept of contra-grav lifters so you didn't count most of the local gravity (some 90+% negated).

MongooseT may have gone back to counting local gravity but I'm not sure having only skimmed the rules.

Now their ship is only capable of 1g acceleration. So ...
How did they get off all those worlds that have greater than 1g surface gravity? o:

And following on from that: How can I let them continue doing so without having to:
a) fudge over what has happened in the past,
b) restrict them to worlds of 1g or less,
c) get them to hire tugs for jobs on >1g planets,
d) upgrade their ship, and/or
e) change the laws of physics?

Some possible answers for the above restrictions may include:

They took on or delivered the cargo and passengers at the HighPort of any worlds with more than 1G local. And if they had any local DownPort business they hopped local shuttles to do it at minimal (petty cash) cost.

Allow them to overdrive their drives for brief periods to allow landing and takeoff. MegaT again introduced this concept for dealing with the problem. Permitting up to 4x overdrive for short periods (to allow ships to rotate from tail sitting on their drive to land on their deck plane instead). The theory being a 1G drive could get you down on a world if the drive were oriented in it's main axis of thrust (usually aft and 90deg to the deck plane), but off axis thrust dropped off significantly (to just 25%), so to land such a ship would require 4x the thrust. If you follow. Basically it permitted one to ignore the issue in a rather lame handwave that failed to see the potential for abuse.

Oh yeah, and wings or similar lifting bodies like mmbutter says If the ship is so equipped, and there is sufficient runway available then that can work to help negate local gravity as well. That will depend on the rules in use and the specifics of the ship in question.

 

[RandyT0001]

Basically one could say that the maneuver drive also negates the gravitational effects of a planet up to it's rating. So a 1 g drive can negate the 1g of Earth then the 1g thrust of the drive is what propels the ship into orbit an beyond. (A 3g drive can negate up to 3g's of a planet's gravity.) If the ship lands on a planet with 1.2g on surface gravity then it will accelerate into orbit at 0.8g since 0.2g has to offset the extra gravity. This will limit a ship with 1g maneuver drives to planets with less than 2g's of surface gravity but very, very few mainworlds will have such a high gravity.
YMMV

 

[Zenguy]

The MegaT solution looks like the one to go with: the maneuver drives counteract local gravity up to the rating of the drive.

 

[socar37]

I'm pretty sure TNE went with counter-grav lifters to negate 99% of the planet's field => what ever maneuver drive the ship had (HEPLAR...blech) was purely for accelleration.

SoCar-37

 

[Supplement Four]

There's a thread that I started on this in the CT forum with some very interesting input by different CotIers.

Early in CT, 1G ships could not make escape velocity from worlds Size 8+. This was changed in later versions of CT (as a detail that was perhaps too persnickety?).

There are some very interesting articles in White Dwarf about this, as well, with suggestions that include disposable rocket boosters that help ships with 1G M-Drives make escape velocity.

Another interesting concept introduced in those White Dwarf issues are the thought that a ship's M-Drive is tied into the ship's inertial compensation, and the ship's captain can only change the interior artificial gravity by lowering the M-Drive rating. Thus, a ship with a 1G drive has the crew sit in zero G as the 1G drive is operating. When the ship is "coasting", after having built up a vector, the 1G rating can be transferred to the ship's compensator allowing for a 1G gravity field.

I think that's extremely interesting and puts a very neat spin on Traveller starships--that a 1G vessel has to have everybody strap down in zero G when the 1G drive is using all its power to accelerate the ship. Once a vector is reached, the power can be transferred to the ship's G-Field, keeping the crew comfortable during most of the trip.

Note that the ship isn't constantly accelerating when this is done, so different travel formulae must be used. And, when it is necessary for the ship to enter combat, the crew must go into zero G.

A ship with a M-Drive rated for 2Gs can have a one G gravity field and constant acceleration at 1G. Or a 2G field with no acceleration. Or 2G accleration while the crew floats in 0G.

See how it works.

I think that's neat.



In the MT Starship Operator's Manual, this topic is mentioned with ships having an "overdrive" capability. Thus a ship rated with a 1G drive can escape worlds of Size 8+.



Me? I prefer the "texture" this type of thinking adds to the game. I like the early CT take on it. It adds a lot to tactics--something to consider for multi-system space combat between fleets. If you're the captain of a vessel with a 1G drive, it can make things interesting.

And, "interesting" leads to roleplaying opportunities.

A Size 8+ world may be accessible by a ship with a 1G drive if it has a high port. The players can take the shuttle down to the planet's surface, if needed. There may be a entire ferry system serving 1G capable starships.

If the world is low tech, then maybe the ship's boat can be used as the 1G vessel orbits the world.

I like the "problems" this poses to the players, and I like how it gives some star systems some character.



Other people just think it is persnickety and therefore also a pain in the arse. Those types can go with MT definition of T-Plates or some other handwave.

 

[shaunhilburn]

e) change the laws of physics?

No change is necessary, just lighten your load.

The existing laws say F=ma, and a=F/m. Say I have a trader massing 200 mtons, with 82 mtons of payload capacity and rated @ F=282 tons of thrust.

With a full payload bay, I have 1 G acceleration. With an empty payload bay, I can pull 1.4 G, even more if I lighten the load with half-full tanks.

The existing laws of physics also say that escape velocity is a scalar value independent of direction.

As long as thrust is applied, an M-drive ship can reach high altitude, and will eventually reach escape velocity (from any world) along any path that doesn't intersect the ground, even in horizontal flight.

A streamlined ship can achieve horizontal flight, even with a thrust-weight ratio < 1. Modern aircraft do it all the time.

 

[far-trader]

Just to clarify...

A streamlined ship can achieve horizontal flight, even with a thrust-weight ratio < 1. Modern aircraft do it all the time.

Streamlined does not always equal Airframe

Modern aircraft employ lifting surfaces and thrust to move air over the lifting surfaces to get airborne. Many streamlined shapes do not have lifting surfaces (or insufficient lifting surfaces) and could not get airborne short of having sufficient thrust to overcome gravity directly. Modern rockets are good examples. Very streamlined shapes, even with fins for control, but no lifting surfaces and totally reliant on producing in excess of 1G thrust to get off the ground.

 

[shaunhilburn]

Streamlined does not always equal Airframe

Even semi-streamlined shapes generate lift, given the right speed.

But my main point was that 1 G ships can land and depart most any world with acceleration to spare, if they go easy on the fuel and cargo.

The type S scout can do even better - with tanks nearly empty and only 10 tons of PP fuel, it should make 2.6 G.

 

[far-trader]

...my main point was that 1 G ships can land and depart most any world with acceleration to spare, if they go easy on the fuel and cargo.

Worth QFTing An excellent point, if the players can manage to employ it

Even semi-streamlined shapes generate lift, given the right speed.

More of a "right shape" (a lifting shape) and/or "correct angle" (of attack) than a "right speed". No amount of speed is going to make a flat square edged surface produce lift edge on.

 

[shaunhilburn]

More of a "right shape" (a lifting shape) and/or "correct angle" (of attack) than a "right speed". No amount of speed is going to make a flat square edged surface produce lift edge on.

Somewhat off-topic, but what is your take on fuel skimming by un-streamlined or semi-streamlined ships? Per CT canon, only fully streamlined ships can skim gas giants.

The rule seems to imply skimming in the denser GG layers, perhaps the troposphere.

 

[aramis]

There are a bunch of solutions across the editions.
Solution 1: Airframe then up. Get up to 1kps, at several dozen km altitude, and then use airframes to redirect most of that up, whilst continuing to thrust. Implied in CT and MT, semi-explicit in TNE/T4, explicit in T20

Solution 2: Gravitics. Presume some form of gravitic technology disconnects local gravity. Explicit in TNE and T4.

Solution 3: overthrust. Explicit in MT "forbidden canon" SSOM, strongly implied in the tables for MT.

Solution 4: boosters. Explicit in MT canon (Hard Times). Strap on extra thrust and blast your way out.

Solution 5: ground based repulsors. Canonical devices in CT (B5), MT, MGT, and T20. Non-canonical application. Ground side throws you at orbit, usually with your assistance.

Solution 6: beanstalk. Run a cable car system from ground to orbit. Beyond OTU tech, per the tables.

There are others.

 

[far-trader]

Somewhat off-topic, but what is your take on fuel skimming by un-streamlined or semi-streamlined ships? Per CT canon, only fully streamlined ships can skim gas giants.

The rule seems to imply skimming in the denser GG layers, perhaps the troposphere.

Only Partially Streamlined (introduced in HG) or Fully Streamlined ships can skim gas giants. In Book 2 only (Fully) Streamlined ships could. Never Un-Streamlined.

My take from the inference is GG skimming is cloud top only in the thinner parts of the atmosphere. To go deeper, such as for lurking below the clouds, or to enter a standard atmosphere would require a Fully Streamlined hull.

Which raises a related caveat for lifting surfaces, you gotta have an atmosphere So they won't help on vacuum or thin atmo worlds. Fortunately the heavy gravity vacuum worlds are rare.

 

[aramis]

High-gravity vacuum worlds are impossible under Traveller rules; no world size 6+ will be sans atmosphere

For non-Mongoose editions...
Size Min Max
_ 0 _ 0 _ 5 _ Vacuum to Thin
_ 1 _ 0 _ 6 _ Vacuum to Standard
_ 2 _ 0 _ 7 _ Vacuum to Standard
_ 3 _ 0 _ 8 _ Vacuum to Dense
_ 4 _ 0 _ 9 _ Vacuum to Dense
_ 5 _ 0 _ A _ Vacuum to Exotic
_ 6 _ 1 _ B _ Trace to Corrosive
_ 7 _ 2 _ C _ VThin to Insidious
_ 8 _ 3 _ D _ VThin to ???
_ 9 _ 4 _ E _ Thin to ???
_ A _ 5 _ F _ Thin to ???

But since 1G is size 8... you have flyable atmosphere, guaranteed, for size 9+

 

[Blue Ghost]

So the party has been roving the sector in a Far Trader pulling whatever cargo and jobs they can find to make their way. In the process they have been on and off worlds of all sizes and atmospheres.

Now their ship is only capable of 1g acceleration. So ...
How did they get off all those worlds that have greater than 1g surface gravity? o:

And following on from that: How can I let them continue doing so without having to:
a) fudge over what has happened in the past,
b) restrict them to worlds of 1g or less,
c) get them to hire tugs for jobs on >1g planets,
d) upgrade their ship, and/or
e) change the laws of physics?

I'm rather hoping the answer is something like: 1g acceleration applies once in space, but the ship has additional grunt when it comes to getting off-planet.

I haven't read the whole thread, so someone else probably answered this already, but 1G refers to the ship's acceleration, it doesn't refer to the force it exerts against a world with a 1G pull. If the later were the case, then you'd have issues

Otherwise you players just accelerate at 9.8m/s^2 regardless of the world (a loophole in the Traveller starship rules).

 

[aramis]

I haven't read the whole thread, so someone else probably answered this already, but 1G refers to the ship's acceleration, it doesn't refer to the force it exerts against a world with a 1G pull. If the later were the case, then you'd have issues

Otherwise you players just accelerate at 9.8m/s^2 regardless of the world (a loophole in the Traveller starship rules).

10m/s², actually, since the traveller G is 10, not 9.8somethingsomething. done that way for math simplicity.