CT Only: GRAVITY! ...And the M-Drive...and Man...and Worlds.

[Supplement Four]

This topic has been controversial in the past. After I had written THIS POST ABOUT SOLDIERS AND CHARACTERS FROM PYSADI, I started thinking about this old (interesting, I think) discussion.



GRAVITY, SHIPS, AND THE M-DRIVE - TOPIC RESURRECTED

Some Traveller players and some White Dwarf Traveller articles (maybe it was just one article--I can't remember) from back in the 70's support the idea that ships with 1G M-Drives cannot make escape velocity from worlds Size 9+.

For easy reference, check out Standard Worlds Template Chart on page 79 of TTB.

The White Dwarf article is interesting because it suggests that disposable boosters can be purchased from a Starport and used to give the ship the extra punch it needs to escape a world with a G field that is over 1G standard.

I've always liked that idea. Many reject it.

I also like the idea that players will have to deal with these types of problems when operating a ship. If you're on the 1G March Harrier, and you call at Reacher, then you've got to make orbit and ferry cargo down to the world using the ship's launch, 13 tons on a trip.

The Harrier makes parking orbit. The side cargo doors are opened. The crew that serve as cargo hands suit up in Vacc Suits and go outside to line up the cargo for easy pick up by the launch on its next return trip. A character or two is on the ground waiting to unload the launch. Everybody has their job.

Aramis (Wil, the CotI member, not the world) has argued in the past that ships like the Harrier, with 1G drives that are also streamlined should be able to use aerodynamic lift to get the ship to escape velocity on Size 9+ worlds. And, I think that's a good idea--but you have to decide which atmo types it can be used. Reacher has an Exotic atmo. I'd say it's up to the Ref as to whether Streamlined ships make a difference on that world for ships with 1G drives.

Note that the rules say that non-streamlined ships cannot enter atmospheres in any case. See page 78 of TTB. So, right there, we've got several classes of ships that cannot land no mater what M-Drive they are using.

Another idea comes from MT's SOM--the idea that M-Drives are capable of "overdrive", where, for a short amount of time (say, while leaving a world, heading for orbit or beyond), a ship's M-Drive can exceed its 1G specification enough to make escape velocity.

I've waffled on that idea over the years, and today, I'd say use it if that's the type of game you want to play. Don't use it if you are like me and want to see some advantages to streamlining...to having a ship's boat...encouragement to high ports, orbital activity, PCs and NPC crews using Vacc Suit skill to load cargo in zero G orbit, and see expenses like starport rented interface cargo craft (not to mention the booster idea, if you like that idea from above).





CANON!

I've wondered how canon this idea is, considering the CT materials. It was a White Dwarf article that first alerted me to the idea--which is hardly canon. But, it all makes a lot of sense to me.

Then, today, I stumbled upon some canon supporting the idea--

Page 16 of Adventure 12 speaks to operations inside a gas giant's gravity well. Ships can operate there if they have 3G M-Drives, which, according to the pg. 79 TTB table, is what is needed to make escape velocity from the Gas Giants listed there.

 

[Supplement Four]

Gravity and Adventure 12

LOCAL GRAVITY AND ADVENTURING



How many of you consider local gravity when playing Traveller? I know that, in the past, I gave it some thought if the PCs were on a low G moon or in Zero G space, but not much outside of those circumstances. I've had encounters where the PCs or the NPC play with the settings on the g-plates inside the ship, too.

I never really bothered with how a character's personal load changes with local gravity. That's one of the uses of the Standard Worlds table on page 79 of TTB. Different Gravity is discussed on page 37 of TTB.

In my Traveller gaming, with regards to local gravity, I didn't want to mess with the effects of gravity on all the PCs and all the NPCs. If the PCs go to Pysadi, it was just like a Star Wars or Star Trek planet--I considered it 1G.

But, I shouldn't do that. And, I won't do that anymore. Pysadi has a local gravity of 0.5 Gs, and that's real important. PCs from a standard 1G environment will be like supermen in certain respects when on Pysadi. Conversely, Pysadians who leave the world will have a real hard time of it when in standard 1G fields.

Spoiler

In TTA, animals from Pysadi (anoloas) are likely stolen from the world, but no thought is given to how living in a 1G standard field would effect the animals.

How long would it take a person to adapt to a new G field? This is something I know little about. If you live your entire life on Pysadi, in that 0.5 G field, then, if you left the world, how long would it take you to adapt to living in a 1 G field? A few months? A few years? A lifetime? Never?

Also: What can the G field say about the people living there? If you are born in a 0.5 G local field, the Ref should describe the Pysadians as then and tall, yes? With weak (comparatively) muscles.

What about lifespan? How would living in a 0.5 G field effect a person's life?





MORE CANON - GRAV BELTS!

Page 16 of Adventure 12 also addresses men in high G fields. The answer is Grav Belts.

I've always thought of Grav Belts as a movement device. You strap them on, and it basically allows you to fly around. It's like a rocket pack, but it operates differently.

But, this page in Adventure 12 opened my eyes as a Referee (to steal a description from Whipsnade) in that its primary use may be to equalize local G fields for characters.

If you're from Pysadi, and you leave that world, you'll have a hard time of it unless you wear a Grav Belt! It is pretty clear from the Adventure that, if you wear a Grav Belt that can handle the local G field, then you can act normally.

Now, I've seen pics of Grav Belts that look like bicycle seats with a hand grip sticking out for control. And, I've seen one that looks like a parachute harness sans the parachute. And, I've seen one that looks like a diver's weight belt, where the weights are replaced with small grav modules. I'm picturing the latter for this instance. You slap on the belt, and you operate normally in a 1G field for as long as the belt operates, even if you were born in, and live your entire life on a world where the local gravity is 0.5G.

 

[AnotherDilbert]

The idea is not farfetched. The starship movement rules on LBB'81 p27-28 explicitly says so. At the surface of a large world you cannot generate a vector away from the planet.

Besides, there are often orbital shuttles available (LBB2'81, p9)

TRADE CUSTOMS
Goods taken on in orbit are delivered when placed in orbit around the destination. Goods taken on on a planetary surface are delivered when off-loaded on the surface of the destination. This custom applies to cargo, passengers, and mail.
At any location with a class A, B, or C starport, shuttles routinely operate between orbit and world surface. Typical shuttle price is Cr10 per ton and Cr20 to Cr120 per passenger.

 

[whulorigan]

Keep in mind that CT'77 and HG1 both presupposed an unspecified Reaction Drive Rocket (Plasma, Fusion, etc) as the standard M-Drive, whereas in later versions of Traveller the presupposition is normally a Gravitic (or Strong-Nuclear Force in MT/DGP) based "reactionless" style drive. That is why in CT'77 burn times were given for small craft and nearly all small craft (except the Launch) have high-G reaction drives for planetary interface, if nothing else.

A gravitic M-Drive may or may not have the limitations mentioned above, depending upon your conception and the ruleset being used.

 

[mike wightman]

Traveller ships do not fly like rockets, they are closer to space planes.

You take off by accelerating in a straight line until lift puts you in the air, you then continue accelerating until your thrust/lift are cancelled by air resistance so you hit your top speed.

Thing is the magic maneuver drive always provides a minimum of 1g thrust regardless, so all you have to do is pull back on the stick, go higher and now you are in thinner air and thus moving faster - it's how planes climb. Once you reach an altitude where the gravity drops below 1g you can now climb out of the gravity well like a rocket, or continue to just gain velocity tangentially to gravity.

The reason for requiring a 3g drive for the adventure is the need to be gravitationally buoyant

 

[Supplement Four]

Traveller ships do not fly like rockets, they are closer to space planes.

You take off by accelerating in a straight line until lift puts you in the air, you then continue accelerating until your thrust/lift are cancelled by air resistance so you hit your top speed.

That's the argument made by Aramis (Wil) that I cite above.

But, the rules say that a vessel, regardless of M-Drive rating, cannot land on a world with an atmosphere. See page 78 of TTB.

So, that's problem one--non streamlined craft. Consider the 200 ton Yacht, for example. M-Drive 1G.

Or the 800 ton Mercenary Cruiser! On Size 9+ worlds, it has to use the module cutters as landing craft even though it's got a 3G M-Drive. It can land on just about any world where atmosphere is not present.



Problem two are worlds where streamlining makes no difference. A 400 ton streamlined Subsidized Merchant does not benefit from its streamlining on a world with Atmo 0 or 1. Depending on the Ref, this definition could be increased to Atmo 2 and 3, or even 4 and 5. Therefore, a Subsidized Merchant could not land on a Size 9+ world if Atmo 0 or 1 (or 2-5, depending on the Ref).



Problem three are the little things that come up but don't happen often. There's Atmo type B and C. Corrosive and Insidious. A ship Captain probably will refrain from exposing his ship to a corrosive atmo, even if he could land--not when he can pay a local shuttle to take his cargo from orbit.

And, an Exotic atmo usually means streamlining will help, but it depends on the exotic nature of the atmo. Maybe it won't support lift for some reason.

 

[Supplement Four]

The biggest change this makes on games is not the ships, but the people. Looking at gravity and the effect it has on humans and other beings.

A character's STR stays the same from chargen, but his load is calculated differently.

But, how do you implement the effect of gravity on a character otherwise? The Pysadi Soldier from the link in the OP, for example. He grows up on a world with 0.5 G, and then he becomes a Traveller--where 1G is typically standard.

How would you implement that in a game. The effect on this Endurance...on his movement. Cut everything in half? Insist on a grav belt being worn at all times, anchoring the character to the life of a powerpack?

Or, do we look elsewhere for appropriate homeworlds for PCs--those ideally at Size 8 worlds, but allowing some variance.



The reverse is true, as well. What about a character from a Size A world? If he is brawling on a Size 8 world, or on the deck of a ship with deck plates set at a standard 1G, does he get a bonus to his damage if he hits? Should he be allowed to make remarkable jumps?

 

[Supplement Four]

But, the rules say that a vessel, regardless of M-Drive rating, cannot land on a world with an atmosphere. See page 78 of TTB.

So, that's problem one--non streamlined craft. Consider the 200 ton Yacht, for example. M-Drive 1G.

Or the 800 ton Mercenary Cruiser! On Size 9+ worlds, it has to use the module cutters as landing craft even though it's got a 3G M-Drive. It can land on just about any world where atmosphere is not present.

In Traveller terms, this is the reason the Nostromo cracked up and needed repairs when landing on LV 426. The ship is not streamlined, and the planetoid is probably type 2 atmosphere. Captain Dallas thought that they'd be able to land, the atmo being "thin", but it was a bit too thick so that the high winds shifted the ship and damaged the landing gear, putting stress cracks on the ship, as it landed on the arduous terrain.

 

[vegas]

Just a little stream of consciousness to a possible house ruling.

I would expect a lifetime in a low-G environment to have these classes of adverse affects:
1) physiological (e.g. low blood levels, early onset of nearsightedness)
2) low strength & endurance
3) low bone mass density

Blood levels recover quickly (a few days) from 0G environment. We don't have enough long-term 0G data to know about other physiological problems that might be out there. Maybe ignore it or assume medical handwavium.

Low STR and END can be recovered with exerecise. As a quick and dirty house rule, I might assert those traits have an "effective" value adjusted by the ratio of G_old/G_new with G_old converging toward G_new at 10% per month. Probably faster with an intense exercise regime.

Low BMD will be significant. Bones will be more apt to break in trip/fall and osteoporosis a risk. BMD can be improved with exercise, but a person that spent adolescence in a low G environment would probably always have significantly lower BMD than another in 1G. Calls for more medical handwavium? In future TL we learn how to stimulate post-adolescent bone growth? Maybe Psyadian's as a culture have agressive resistance-training of adolescents to increase bone calcium carrying capacity? I don't know. Up to you if you want to play with it or make it go away.

 

[Supplement Four]

Blood levels recover quickly....

Low STR and END can be recovered with exerecise....

Assuming the body was once used to 1G. What about those who were born in 0.5 G with bodies who have never operated for any long period of time in a 1G field?

 

[Supplement Four]

Traveller Homeworlds

The Local Gravity question creates a restriction on PC homeworlds--for those people thought idea candidates to become Travellers.



A Size 8 world is, of course, the ideal world for a person transitioning into the Traveller class.

Or, anyone who lives in space, like a Belter, living on a station with a 1G field.

Anybody from a Size 9+ world would work, too, since he'll be stronger and have more Endurance than a standard 1G character.

And, anyone from a Size 7 world would work, too, since we're talking about a 14% loss of STR/END.

I would think that anyone from Size 6- worlds are not prime candidates to become Travellers unless the world's TL is high enough so that all structures are built with 1G grav plates. With tech bleed, we're talking about TL 7 or TL 8 or better worlds.

 

[aramis]

Current NASA data strongly implies that 6 months in zero G produces permanent reduction of bone density.

Several astronauts have commented that they've never fully recovered from even several weeks in space.

 

[mike wightman]

Ever watched the Expanse?

 

[AnotherDilbert]

Traveller ships do not fly like rockets, they are closer to space planes.

Do we have an explicit source for that?

SSOM (although not CT) says otherwise.

 

[Supplement Four]

Current NASA data strongly implies that 6 months in zero G produces permanent reduction of bone density.

Several astronauts have commented that they've never fully recovered from even several weeks in space.

So, what's the answer? Everyone gets a grav belt as standard equipment on their Vacc Suits?

 

[BlackBat242]

Current NASA data strongly implies that 6 months in zero G produces permanent reduction of bone density.

Several astronauts have commented that they've never fully recovered from even several weeks in space.

Lets see the results of this study in a couple of years' time... this will give a better idea.
https://www.nasa.gov/twins-study/

http://www.theverge.com/2017/1/29/14424900/nasa-twins-study-mark-scott-kelly-gene-expression-dna

 

[Supplement Four]

Although there seems to be absolutely nothing in canon about this (canon covers load with respect to gravity, and it covers ageing difference with how the Jump Drive works and anagathics, but not this?), I do like the idea of some medical breakthrough.

So...you're on Pysadi, having lived your entire life at 0.5 G, and you want to join the ranks of Travellers.

You've got to undergo what the call THE TREATMENT!

It's a program of drugs and physical therapy that....



(T5, for all its failings, has A LOT of good ideas and topics addressed in it. I wonder...if...there...is anything on this.... I'll have go digging.)

 

[Supplement Four]

Looking through T5...

I'm looking through T5 for something else, but I see that the idea is carried through to that edition of the game.

Page 364: If the Drive cannot produce acceleration equal to local gravity, the ship impacts on the surface at Speed=13.

 

[kilemall]

I opened up this can of worms in the Fleet forum. Quite a bit of discussion on it.

http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=34502

I ended up with ships could have reaction M-drive, grav M-drive, or combinations thereof (mostly because I want a lot of action out in The Cloud, where there isn't a lot of gravity to be anti- against), that 1-G ships CANNOT normally just use their M-drive to leave but that there is an afterburner option for reaction burners (double G, for every 100 seconds it's doubled a day's worth of fuel is burned and damage chance rolls start accruing, 1- for first 100 seconds and an increase of 1 per 100s, so by 300 seconds of burn its 3- for M-drive damage, etc.).

Have damage for exceeding G tolerances for hours when exceeding gravitic compensator limits.

As for gravitic effects on PCs, I've always had a -1 STR for low/zero G and +1 for high G childhoods and assumed great lengths were taken to normalize for human development, at least for childhood. This means child nurseries/schools on otherwise inhospitable near-G worlds, or orbitals with spin or artificial gravity. This works IMTU given the 'opening of space' vibe and at least TL8-9. May not work for OTUs.

 

[vegas]

Blood levels recover quickly....

Low STR and END can be recovered with exerecise....

Assuming the body was once used to 1G. What about those who were born in 0.5 G with bodies who have never operated for any long period of time in a 1G field?

For blood supply, there is no physiological reason why going from 0.5G to 1G is any different from going from 1G to 0G (except that the sign on the change is different). Bodies are very good at maintaining homeostasis for BP, especially for fit, healthy individuals. Change in gravity results in change in the amount of blood that is pooling in lower extremities which in turn changes the BP in the brain. The body maintains homeostasis by increasing or decreasing blood supply to get back to normal BP. Our 0.5Ger in a 1G environment will feel light headed and very thristy for a few days until their body obtains homeostasis and returns brain BP to normal. It is like they lost a lot of blood. Recovery could probably be sped up with transfusions.

As for recovery of muscles (STR & END) versus only ever had 0.5G muscles, muscle mass doesn't have the same physiological constraint on being built later in life that bone density does, so it isn't the same kind of road block. A strong, fit 0.5Ger can undergo an intense exercise regime and get into 1G shape. It just takes time. (Assuming of course their bones can handle stress and mass, but based again on NASA, returning conditioning isn't the issue as much as bone density itself.)

Which brings us back to bone mass density.

So... we could assume the Pysadian Presidential Medal of Fitness is awarded annually to children through teenagers achieve demanding exercise metrics consistent with the achievement of normal 1G bone mass.

or, if we think that is too exotic of a concern and Pysadis are otherwise fine with the naturally petite forms, then we have instead

So...you're on Pysadi, having lived your entire life at 0.5 G, and you want to join the ranks of Travellers.

You've got to undergo what the call THE TREATMENT!

It's a program of drugs and physical therapy that....

with stem-cell cocktails re-stimulating bone growth post-adolescence and nano-surgically infused mineral-rich serum for increased bone strength and calcium carrying capacity... er whatever.

So, what's the answer? Everyone gets a grav belt as standard equipment on their Vacc Suits?

A space walk isn't going to be any more harmful than a dip in a swimming pool. Grav belt not required. It is the extended time that makes the difference. Since Travellers spend almost all their time under 1G due to deck grav plates, lost BMD won't be the issue it is for NASA guys that experience 0G for days on end.