1g Ships and Size:7 worlds...

[Grav_Moped]

Note heat is less of a issue within a atmosphere... Just sayin'
Even with one g if you can get it to fly, you can get it into orbit.

Though, when I think of traveller ships I rarely worry about Supersonic speeds.

Rule of Cool. If it looks streamlined, it is streamlined enough.

But even at 2G, a ship is probably going transonic in a standard atmosphere on the way up, if they don't intentionally throttle down.

 

[infojunky]

But even at 2G, a ship is probably going transonic in a standard atmosphere on the way up, if they don't intentionally throttle down.

Depends, no need if you can lift straight up. Consider how thin the puddle of air is. Meaning that speed of sound gets lower the higher you get, while you are "supersonic" your speed can be fairly constant.

 

[Grav_Moped]

Depends, no need if you can lift straight up. Consider how thin the puddle of air is. Meaning that speed of sound gets lower the higher you get, while you are "supersonic" your speed can be fairly constant.

That's the thing. Even today's rockets throttle back at max-Q (maximum dynamic pressure).

 

[Grav_Moped]

(Revisiting for clarity)

Depends, no need if you can lift straight up.

Exactly. In the context of MD>Local Gravity, it's possible to reach orbit at a brisk walking pace if you're patient enough.

 

[infojunky]

(Revisiting for clarity)

Exactly. In the context of MD>Local Gravity, it's possible to reach orbit at a brisk walking pace if you're patient enough.

Yep...

if you gots thrust, things are much easier, Even with a nominal amount.

 

[Spinward Flow]

I'm still amazed that after over 200+ replies to this thread, there is so much investment in denying that 1G thrust against 1G of gravity results in a performance profile that looks remarkably like this ...

Also known (to Astra, who failed the launch shown here) as "You Are Not Going To Space Today."

If you want to "go to space today" RELIABLY, you are going to need a maneuver drive acceleration greater than that of the local gravity.

Yes, streamlining can help with atmospheric lift on worlds that have (suitable) atmospheres ... but not all 1G+ worlds in charted space have atmospheres that will be "dense enough" for streamlining to make use of so as to provide enough aerodynamic lift to gain altitude (and "Go To Space Today").

Exactly. In the context of MD>Local Gravity, it's possible to reach orbit at a brisk walking pace if you're patient enough.

I'm sorry, but if it's going to take hours/days/weeks/months/years to get to orbit ... you're probably not meant to be using the system you're trying to achieve this particular maneuver with in that way. Yes, an air/raft can "fall up" for 6 hours to (finally) reach orbit, according to LBB3, but that's hardly the main (or even primary) use case for such a vehicle.

 

[Grav_Moped]

If you want to "go to space today" RELIABLY, you are going to need a maneuver drive acceleration greater than that of the local gravity.

Pretty much.

but not all 1G+ worlds in charted space have atmospheres that will be "dense enough" for streamlining to make use of

Not all, but most, if the worldgen rolls represent in-game reality. Wouldn't want to try it in a corrosive atmosphere though.

Yes, an air/raft can "fall up" for 6 hours to (finally) reach orbit, according to LBB3, but that's hardly the main use case for such a vehicle.

If it's what you've got, you do it. More to the point, if that's what you're primarily doing with it, it's probably going to look more like an overgrown re-entry capusle than a flying convertible. If you don't have a lot of lateral thrust for deceleration, aerobraking is fast and almost free.

 

[atpollard]

Yes, streamlining can help with atmospheric lift on worlds that have (suitable) atmospheres ... but not all 1G+ worlds in charted space have atmospheres that will be "dense enough" for streamlining to make use of so as to provide enough aerodynamic lift to gain altitude (and "Go To Space Today").

“Dense enough” is an interesting phrase when real rocket scientists view the atmosphere of MARS as “dense enough” to explore for atmospheric breaking and glider landings. I wonder just how far down the Traveller Atmospheric chart Mars falls.

Sure, I acknowledge that lunar gliders are a bad idea… but just how many giant planets with no atmosphere are there really likely to be? Too much gravity to take off, but not enough to capture gases? A VENUS atmosphere is probably a greater danger as worlds get larger. Then we can have “aerostat assisted launches”.

 

[Grav_Moped]

“Dense enough” is an interesting phrase when real rocket scientists view the atmosphere of MARS as “dense enough” to explore for atmospheric breaking and glider landings. I wonder just how far down the Traveller Atmospheric chart Mars falls.

Sure, I acknowledge that lunar gliders are a bad idea… but just how many giant planets with no atmosphere are there really likely to be? Too much gravity to take off, but not enough to capture gases? A VENUS atmosphere is probably a greater danger as worlds get larger. Then we can have “aerostat assisted launches”.

Atm=2D-7+Size. Rather low odds of anything less than Very Thin.

 

[whartung]

I'm still amazed that after over 200+ replies to this thread, there is so much investment in denying that 1G thrust against 1G of gravity results in a performance profile that looks remarkably like this ...

But here's the thing.

We are told, as we understand it, as presented throughout the canon of the game, that the 200 ton, 1G Free Trader is as common as dirt, and thereby, a viable, even profitable ship.

We also have the common trope of the same Free Trader, sitting quietly in the sunlight, on the tarmac of the starport as vehicles and crews service and load/unload the ship.

The Free Trade is THE ship of the Traveller Universe. Free Trader Beowulf, is that you? Hopping on and off it ala Firefly is THE "thing" of Traveller. "Travellers" travel on their own Free Trader or buying a ticket on someone else's. It's a key component of the adventure of Traveller, as core to the universe as Jump is to communication.

So.

Somehow, someway, lifters, wings, anti-grav, 1000's of helium balloons ala Up, the Free Trader is getting on and off 1G, even 1G+, worlds, safely and efficiently. This is a "solved problem".

If this were such a big deal, there'd be some nice bold text on the Free Trader ship description: "Don't forget, if you plonk this down on that Starport C, 10,000km diameter world, you're stuck. So, don't do that or the bank will be really ticked off."

The only limitation to a ship landing on a planet is whether it's streamlined or not.

If an ATV is carried, provision must be made to move it to a world surface if the ship is not streamlined, unless, of course, the vehicle is intended for use only on worlds without an atmosphere.

Note it doesn't say anything about "if the ship is not streamlined or does not have a large enough Maneuver Drive to overcome the planets gravity". That would be an important detail.

How do birds fly? Dunno, but I see birds fly every day. How do Free Traders take off of larger worlds? Dunno, but apparently they manage just fine.

 

[Grav_Moped]

How do birds fly? Dunno, but I see birds fly every day. How do Free Traders take off of larger worlds? Dunno, but apparently they manage just fine.

Birds aren't real. (birdsarentreal.com)

 

[Spinward Flow]

Somehow, someway, lifters, wings, anti-grav, 1000's of helium balloons ala Up, the Free Trader is getting on and off 1G, even 1G+, worlds, safely and efficiently. This is a "solved problem".

If this were such a big deal, there'd be some nice bold text on the Free Trader ship description: "Don't forget, if you plonk this down on that Starport C, 10,000km diameter world, you're stuck. So, don't do that or the bank will be really ticked off."

You are making a fundamental flaw in assumption.

The classical J1/1G Free Trader has no problem "getting on and off" MOST worlds "safely and efficiently" ... is a TRUE statement.

Conflating that prior fact with the notion that the J1/1G Free Trader can (ipso facto) "get on and off" ALL worlds "just as safely and just as efficiently" no matter what ... is an error of first principles.

The Free Trade is THE ship of the Traveller Universe. Free Trader Beowulf, is that you? Hopping on and off it ala Firefly is THE "thing" of Traveller. "Travellers" travel on their own Free Trader or buying a ticket on someone else's. It's a key component of the adventure of Traveller, as core to the universe as Jump is to communication.

The J1/1G Free Trader is perfectly serviceable for downport landings on MOST worlds.
However, there are going to be SOME worlds where you'll only get to try that maneuver once (because lithobraking "is a thing" you NEVER want to have to do!) ... and it's important for both Players and (even more importantly) Referees to recognize locations where a local gravity well could become potentially problematic, either for descent from or ascent to orbit.

Sometimes you'll be able to "get away with" a bit of cleverness, leveraging an atmosphere for lift using a streamlined hull ... but not necessarily in ALL cases and contexts. Sometimes though, the atmospheric lift option simply won't be available (for whatever reason) ... with the most obvious one being a lack of infrastructure support at wherever your landing site is. Most type E and X starports are unlikely to have any kind of liftoff assistance services available, and the same would hold true for a "water landing" in an ocean or a lake for a wilderness refueling maneuver.

So depending on the context ... you can either be SAFE or SORRY.
Choose wisely ...

 

[Grav_Moped]

Two different ways to look at it here: Rules as written say, "no". Rules as actually played say at least "maybe".

It's down to how crunchy and nit-picky you want your setting to be.

 

[Condottiere]

You have to go through the rules with a fine tooth comb, and I don't think you can overclock with Classic.

 

[AnotherDilbert]

Two different ways to look at it here: Rules as written say, "no".

Agreed.

Rules as actually played say at least "maybe".

That was a very round-about way of saying "house rule". Yes, you can house rule whatever you want, including this.
But, it's your house rule, and does not apply to all Traveller Universes.

Somehow, someway, lifters, wings, anti-grav, 1000's of helium balloons ala Up, the Free Trader is getting on and off 1G, even 1G+, worlds, safely and efficiently. This is a "solved problem".

Sure, if you want your Traveller Universe to work that way, it does, no need to motivate.
But, it's your house rule, and does not apply to all Traveller Universes.

 

[mike wightman]

Traveller ships are not rockets. Most ACS are belly landers according to the deck plans.

Traveller ships are streamlined and have at least 1g continuous thrust engines - higher thrust than the vast majority of aircraft, even military.

Here are the relevant rules:

Atmospheric Streamlining: A starship may be streamlined when constructed,
allowing it to enter atmospheres for landings. LBB2 77

Atmospheric Streamlining: The hulls specified are rough deep space configurations incapable of entering atmospheres. They may be streamlined by indicating in the design plans, at a cost of MCrl per 100 tons of ship. This streamlining
includes fuel scoops which allow the skimming of unrefined fuel from gas giants and the gathering of water from open lakes or oceans. LBB2 81 et al

Any ship can land on a world with an atmosphere of 0 or 1; for all other worlds, streamlining is required. LBB5 79

Any ship of configuration 1 to 6 can land on a world with an atmosphere 0 or 1; for all other worlds, streamlining is required.
Streamlining refers to the ability of the ship to enter atmosphere (partial streamlining allows fuel skimming. but prohibits entry into world atmospheres for the purpose of landing LBB5 80

No mention of a world size limitation in all those rule books.

So here is how a 1g ship gets to orbit:
1 - take off like a plane
2 - climb as fast as possible to the weight/drag balance altitude
3 - maintain this altitude but continue to accelerate horizontally until orbital velocity is achieved.
4 - inertial orbital insertion above the 1g threshold, the ship is now free to accelerate to a higher orbit or accelerate away from the planet.

Note that this will require a Traveller streamlined ship to be capable of transonic and hypersonic flight. but then the m-drive does generate a field that can deflect radiation (canonical) - this is likely to be a magnetic field. magnetic fields can contain and shape plasma, you can work out the rest.

 

[AnotherDilbert]

No mention of a world size limitation in all those rule books.

Striker, B2, p41:
_ _ A. Movement: The movement rate of a spaceship is determined in the same way as that for a grav vehicle; the ship's maneuver drive rating is used as its G value. A ship with a G rating equal to or less than the planetary gravity may not take part in combat actions except from orbit.

You choose the rules that suits you, and ignore the rest. Even then, you rely heavily on what they don't say, rather than what they do say. Note that there is no mention of lift anywhere, only "ability of the ship to enter atmosphere".

So here is how a 1g ship gets to orbit:
1 - take off like a plane
2 - climb as fast as possible to the weight/drag balance altitude
3 - maintain this altitude but continue to accelerate horizontally until orbital velocity is achieved.
4 - inertial orbital insertion above the 1g threshold, the ship is now free to accelerate to a higher orbit or accelerate away from the planet.

Yes, they do: In your TU, with your house rules.

But not in my TU, as I haven't bothered to house rule that particular trivia. I have plenty of other house rules, what's the big deal?

 

[Spinward Flow]

No mention of a world size limitation in all those rule books.

Striker, B2, p41:
_ _ A. Movement: The movement rate of a spaceship is determined in the same way as that for a grav vehicle; the ship's maneuver drive rating is used as its G value. A ship with a G rating equal to or less than the planetary gravity may not take part in combat actions except from orbit.

You choose the rules that suits you, and ignore the rest. Even then, you rely heavily on what they don't say, rather than what they do say. Note that there is no mention of lift anywhere, only "ability of the ship to enter atmosphere".

Have to agree with @AnotherDilbert here on this one, but I've got even more corroborating evidence that you neglected to look for.
LBB2.81, p26-37 deals with Space Combat and (wait for it) ... vector movement!

Specific (repeated!) mentions of gravity in vector movement are highlighted in bold text.
Note that the "standard design type A free trader" IS DIRECTLY MENTIONED within the vector movement rules.

LBB2.81, p27:

MOVEMENT
In clear space, without gravitational influence, and without voluntary acceleration by the ship, it could travel [...] forever.

LBB2.81, p28:

Acceleration involves altering a ship's vector by adding another to it; this new vector can come from thrust using the maneuver drive, or it can come from gravity. In either case, the method is the same

LBB2.81, p28:

Ships are restricted in the amount of acceleration which they may add to their current vector in one movement phase. Generally, a ship cannot accelerate more than 100 mm times its maneuver drive rating in Gs. Thus, a standard design type A free trader is capable of 1G acceleration, and cannot add more than a 100 mm vector per turn. This does not count acceleration due to gravitational influence

LBB2.81, p28-29:

GRAVITY
The section on planetary templates later in this chapter covers the construction on specific world disks, complete with gravitation bands which can affect movement. When the vector of a ship passes through the gravity bands of a world, the gravity may alter that vector.
[...]
The gravity vector is parallel to a line connecting the regular course midpoint to the planetary template center. It is added to the regular course vector (along with any ordinary course change vector) during a player's movement phase.

LBB2.81, p31:

lntruder Player Turn-
A. lntruder Movement. The intruder moves his ships using the movement, gravity, and other applicable rules.

A. Native Movement. The native moves his ships using the movement, gravity, and other applicable rules.

LBB2.81, p36-37 even has formulas and a table for easy use to determine gravity bands around planetary surfaces.
Note that the table provided on LBB2.81, p37 specifically details the surface gravity of Size: 8+ worlds (at 1.000G, 1.125G and 1.250G respectively).

• Size: 7 = 0.875G - 1G = -0.125G vector
• Size: 8 = 1.000G - 1G = +0.000G vector
• Size: 9 =1.125G - 1G = +0.125G vector
• Size: A =1.250G - 1G = +0.250G vector

Not to put too fine a point on things that ought to be beyond obvious enough already ... but you need to achieve a "negative G vector" if you want to Go To Space Today™ from a planetary surface. That's just vector math for you!

Also, LBB2.81, p28 includes this tidbit:

Unused acceleration may not be saved or conserved to allow excess acceleration in following turns.

In other words ... THERE IS NO OVERCLOCKING of maneuver drives available for "bursts" of maneuver in CT.



Extra bonus points to anyone who reads through LBB2.81, p26-37 and realizes that "atmospheric LIFT due to streamlining" is conspicuously absent from any mention AT ALL as an available modifier to movement vectors for starships and small craft. In fact, the closest thing you can get to the notion is (wait for it) ...

LBB2.81, p34:

Atmospheric Braking: Ships passing very close to the surface of a world with a standard or dense atmosphere may slow their speed through atmospheric braking. If any portion of a ship's vector passes within 10 mm of a world's surface, that vector is reduced by 10 mm in length.

Last I checked, being on the surface of a planet with a standard or dense atmosphere counted as being within 1000km (10mm using the vector movement scaling) of a planet. So a Standard or Dense atmosphere adds a 0.1G drag force to vector movement under LBB2.81 (and LBB2.77 for that matter)!

So if we circle back to our vector math assumptions that resolve movement vectors and add in the atmospheric DRAG (not lift! drag!) of Standard and Dense atmospheres, we get this result:

• Size: 7 = 0.875G + 0.1G - 1G = -0.025G vector
• Size: 8 = 1.000G + 0.1G - 1G = +0.100G vector
• Size: 9 =1.125G + 0.1G - 1G = +0.225G vector
• Size: A =1.250G + 0.1G - 1G = +0.350G vector

So a "standard design type A free trader capable of 1G acceleration" CAN LIFT OFF from a Size: 7 world (0.875G) at either 0.125G vertical (Atmosphere: 5-) or agonizingly slowly at 0.025G vertical (Atmosphere: 6-9) under LBB2.81 vector movement RAW.

That same "standard design type A free trader capable of 1G acceleration" is going to remain FIRMLY MIRED in the gravity well of any Size: 8+ world ... and adding Atmosphere: 6-9 only makes things WORSE ... not better!

No mention of a world size limitation in all those rule books.

BECAUSE THEY DIDN'T HAVE TO.

Any tabletop wargamer who can compute vector math in their head could figure it out (for themselves!) VERY VERY QUICKLY.

 

[ManOfGrey]

You only need lift and weight to balance, you keep accelerating "horizontally" until you have achieved enough velocity for an inertial orbital insertion above the 1g threshold.

Its an orbital mechanics problem which is a little bit more involved then the simple equation you posted.

You have a good point. But, that too, is calculable.

On Earth, at least, to reach the International Space Station, (the altitude required for a 1G capable starship to be able to pull away from a 1.125 G gravity well,) a rocket has to reach a speed of 25,000 mph... or Mach 32.6.

 

[mike wightman]

You choose the rules that suits you, and ignore the rest. Even then, you rely heavily on what they don't say, rather than what they do say. Note that there is no mention of lift anywhere, only "ability of the ship to enter atmosphere".



Yes, they do: In your TU, with your house rules.
But not in my TU, as I haven't bothered to house rule that particular trivia. I have plenty of other house rules, what's the big deal?

No, I am using the rules laid out in the space combat games. So are you saying lift and drag do not exist in the Traveller setting and that planes therefore can't fly?

Striker is not LBB2 and deals with grav modules not maneuver drives, it contradicts what is already stated for ships (in that they can enter atmospheres).

Or are you saying 1g ships can't fly at all regardless of streamling because of what Striker says?

No big deal, I just enjoy the discussion, provided it is civil of course