1g Ships and Size:7 worlds...

[Condottiere]

Ignoring rockets, primary or assist, if we could fractionally overclock a manoeuvre drive factor one by maybe a third or so.

Otherwise, we'd need a technological level eleven manufactured manoeuvre drive factor sub two, instead one that's technological level nine.

 

[Spinward Flow]

Otherwise, we'd need a technological level eleven manufactured manoeuvre drive factor sub two, instead one that's technological level nine.

In a LBB5.80 custom drives paradigm, you are indeed correct that TL=11 is required for J2 ... but you can achieve M6 as early as TL=9, and M3-5 even earlier at TL=8.

In a LBB2.81 standard drives paradigm, TL=9 drives are good for J2/M2 up to 400 ton displacements ... and TL=10 drives are good for J2/M2 up to 800 ton displacements.

So for low end ACS type designs, you're looking at TL=9-10 for 2G drives in the 100-800 ton starship form factors, not TL=11.
An honest mistake to be sure (I've made it myself before, so no hard feelings).

 

[Condottiere]

Oh right, they're software locked.

 

[Grav_Moped]

Oh right, they're software locked.

Yeah. It's a TL-based subscription model: Space Drives As A Service.
[Click here to enable convenient automatic payments for the features you deserve.]

 

[infojunky]

In a LBB5.80 custom drives paradigm, you are indeed correct that TL=11 is required for J2 ... but you can achieve M6 as early as TL=9, and M3-5 even earlier at TL=8.

Note in LBB5.79 Power 6 is TL12, these Maneuver 6 isn't available until power is met.

Note in TNE G-Compensation is limited to 4gs at TL12....

 

[Condottiere]

Yeah. It's a TL-based subscription model: Space Drives As A Service.
[Click here to enable convenient automatic payments for the features you deserve.]

I'm not sure I'd be onboard with the subscription model.

 

[atpollard]

Oh right, they're software locked.

Or a dongle to insert in the port … “Where the heck is that HASP! I told you to put it back on the hook when not in use.”

 

[atpollard]

I once designed a 100 dTon J1-1G ship made from the hulls of two 50dT Modular Cutters that could uncouple. One “hull” could then function as a 50dT 2G Cutter with a detachable cargo module and the other “hull” stayed in orbit with the Jump Drive and Starship Bridge. (Plus a second cargo/fuel module).


That was during my “what can you do with a 30 dT cutter module” phase.
(you should see some of the space stations that you can build).

 

[Condottiere]

Would be edition specific.

Under the current updated High Guard, upto fifty tonnes of volume can be bridged with a one and a half tonne cockpit.

Have three of those with independent propulsion, plus a master with a six tonne (small) bridge, twenty tonne fuel tank, and a ten tonne jump drive.

 

[atpollard]

Would be edition specific.

What isn't?

Under the current updated High Guard, up to fifty tonnes of volume can be bridged with a one and a half tonne cockpit.

OK ... I was always PERSONALLY fond of the 2% and 10% guidelines from CT [Although not always a fan of how the Rules-As-Written applied them and the Ships-As-Drawn ignored them]. As a PERSONAL taste, I would have gone with 10% for "Boats" (non-Starship) with a 0.5 dT minimum and a 10 dT maximum and 2% for Starships with a 10 dT minimum and no maximum (although over 20 dT of bridges should probably be split into multiple smaller bridges). Sadly, I didn't get to write the rules.

I don't remember the exact details of my design except that CT Plans CLEARLY reallocated Bridge Tonnage around the ship, so I felt justified in dividing a bridge in HALF (warships have multiple bridges linked together) and placed the MD half of the Bridge in one 20 dT hull and the JD half of the bridge in the other 20 dT hull (plus two 30 dT removable modules makes 100 dT ... the smallest allowable starship).

Have three of those with independent propulsion, plus a master with a six tonne (small) bridge, twenty tonne fuel tank, and a ten tonne jump drive.

Oh, Yeah ... I definitely experimented with other combinations ... including a pair of "cutters" with an open Jump-frame that will hold a bunch of 30 dT cutter modules [I think it was 600 dT total].

I also built a "hamster wheel" rotating station with 30 dT modules linked to a simple corridor/framework ... but that is getting away from the >1G world problem [unless you deliver cargo & passengers to ORBIT at the "Hamster Wheel"].

 

[ManOfGrey]

While it doesn't solve the problem of a 1G lifting off of a 1G planet. What I tried in Orbiter Space Simulator is to model a ship that had a m-drive for thrust, and a second m-drive mounted on a swivel that would rotate to point to the local gravity vector. The 2nd M-drive would negate the local gravity vector allowing thrust m-drive to be whatever size large or preferably small to get the travel time you want.

For what it's worth, there was an interesting starship in T4 that I don't believe I've seen anywhere else -- the "Military Landing Ship Infantry." Built at a lower tech level, (TL-11,) it incorporated a system using two drives, like you mentioned above... only one was Gravity Thruster Plates, the other was a HELPlaR drive. While I doubt the designer had this application specifically in mind, it does offer a unique solution to the quandary of trying to take off in a ship with a only a 1G capability from a "Super-Earth" that has a surface gravity that exceeds 1G.

The Gravity Thruster Plates can generate a 1G acceleration indefinitely, while the HELPlaR drive can produce an additional 1G for 11 hours. I would think that's plenty of time to get to orbit at 2Gs.

Anyway... one of those things that make you say "hmmm...."

 

[AnotherDilbert]

Built at a lower tech level, (TL-11,) it incorporated a system using two drives, like you mentioned above... only one was Gravity Thruster Plates, the other was a HELPlaR drive. While I doubt the designer had this application specifically in mind, it does offer a unique solution to the quandary of trying to take off in a ship with a only a 1G capability from a "Super-Earth" that has a surface gravity that exceeds 1G.

It's a perfectly normal thing to do in TNE and at lower TLs in T4. It's generally done to make landings easier. OK, a bit weird at TL-11.

1 G is all you need to get to the jump point, but you might temporarily need a bit more to land (explicitly in those editions).


The normal combination is Contragrav and HEPlaR:

T4 FF&S, p65:
Contragravity is used mainly by grav vehicles for lift and propulsion. However, spacecraft often also mount contragravity to assist in takeoff and landing, especially on worlds where the local gravity is greater than the ship's main maneuver drive's rating.

 

[Condottiere]

Large enough wing area.

 

[Spinward Flow]

Large enough wing area.

Except ... there'a a problem with that approach.

Atmospheres on different worlds are different.
What is "awesome" aerodynamically on one world in one type of atmospheric composition and pressure will be totally inadequate on a different world with a different atmosphere. In other words, you can't just assume that a "large enough wing area" for one specific world gravity and atmospheric composition will work equally well for ALL worlds and ALL atmospheres.

This is where the fact that starships are meant to be interstellar and therefore travel to different worlds (with different surface gravity ratings and atmospheres) becomes a problem. You can't always rely on the "oh I've got wings, so I'm covered" excuse in all contexts. SOME contexts, sure ... but ALL contexts, no.

Now, granted ... Size: 8+ worlds will tend to have atmospheres (because that's how gravity works) ... but that's not my point. My point is that a variety of Size: 8+ worlds might not have the right KIND of atmosphere that lets you "get away with" the Large Enough Wing Area solution to the problem in all cases.

 

[Condottiere]

For some strange reason, Terran norm gravity synchronizes with technological development of gravitational propulsion.

So factor one zeroes off let's say a Terran norm planet, with presumably Terran norm gravity.

Any gravity well with under Terran norm gravity, the object is not only going to just levitate, but float away.

 

[Jame]

In my CTU, all ships that have a maneuver drive of 1g or better also have a shipboard gravity generator so the crew isn't always in 0G in space.
And they also have an anti-gravity system, just like those TL-9 air/rafts do.

 

[Grav_Moped]

Except ... there'a a problem with that approach.

Atmospheres on different worlds are different.
What is "awesome" aerodynamically on one world in one type of atmospheric composition and pressure will be totally inadequate on a different world with a different atmosphere. In other words, you can't just assume that a "large enough wing area" for one specific world gravity and atmospheric composition will work equally well for ALL worlds and ALL atmospheres.

This is where the fact that starships are meant to be interstellar and therefore travel to different worlds (with different surface gravity ratings and atmospheres) becomes a problem. You can't always rely on the "oh I've got wings, so I'm covered" excuse in all contexts. SOME contexts, sure ... but ALL contexts, no.

Now, granted ... Size: 8+ worlds will tend to have atmospheres (because that's how gravity works) ... but that's not my point. My point is that a variety of Size: 8+ worlds might not have the right KIND of atmosphere that lets you "get away with" the Large Enough Wing Area solution to the problem in all cases.

Size 8+ worlds have Atm 2D+1 (2D-7+Size). This yeilds a minimum atmosphere of 3: Very Thin -- and Standard or better on a roll of 5+ (83% of the time) for Size 8, lower and far lower for Size 9 and A respectively.

In the subsonic speed regime, aerodynamics is just airspeed and air density. Airfoils work the same way throughout this range, they just need higher airspeed in thinner air. This does mean varying stall speeds, and that the speed at which Mach 1 occurs also varies. It's a problem for air-breathing engines, as their available power falls off with reduced atmospheric density (that's assuming a standard oxygen fraction, too...) Starship drives don't have this issue.

The implication from the LBB3 worldgen table is that Atms A, B, and C are denser than Atm 8-9 -- though this is only an implication, so it might not be universally valid.

 

[Captain_Ahab]

I don't think anyone really wants to go down the aerodynamics rabbit hole in a reasonable fashion
For the sizes and the speeds for ships in Traveller, etc. it is just impracticable or else just a handwave anyways.
And that's without worrying about mach cones and shock waves*.
In Traveller, ship's mass will make for really high wing loading, too, so stall speeds will be high, as will ground pressure for runways.

* shock waves will be a problem.
Consider the Myasishchev M-25 Hell Reaper, a Soviet weapon that didn't move out of the research stage
cool looking airplane though



Article describing the M-25 Hell Reaper

 

[Grav_Moped]

shock waves will be a problem.
Consider the Myasishchev M-25 Hell Reaper, a Soviet weapon that didn't move out of the research stage
cool looking airplane though

The US thought of it first, though the weaponized sonic boom was merely a side-effect.
It could have dropped up to 26 separate nuclear weapons.
Supersonic Low Altitude Missile (Wikipedia)

Added bonus: Radioactive exhaust! (Yes, powered by an atomic ramjet -- and we actually built and tested the engines.)

 

[Grav_Moped]

Better use of shock waves: XB-70 Valkyrie (Wikipedia)

The fold-down wingtips trapped the shockwave from the engine inlet under the aircraft to maximize compression lift.

Regrettably, advances in radar technology rendered it obsolete before it entered production.