1g Ships and Size:7 worlds...

[AnotherDilbert]

At say 50 km altitude the atmosphere is basically gone, but gravity is still over 99% of surface gravity.

You have to achieve close to orbital velocity IN the atmosphere, because out of the atmosphere is too late, the ship will fall back again.

What's the drag on a Mach 20 brick?

 

[mike wightman]

Less than that required to prevent it flying into orbit with a 1g continuous thrust engine and TL9 control surfaces and flight computer.
Not to mention you can use inertia to get above the 1.00g line at which point you can accelerate to orbit anyway.

 

[AnotherDilbert]

For a size 8-A world build your starport at altitude and use your streamlining to generate enough lift to fly to orbit. Traveller ships fly in atmosphere like planes, they do not fly like rockets.

At altitude air pressure is lower so take off speed is higher, needing much longer runways.

You should take off at high air pressure, low altitude, for lower take off speed and shorter runways.

 

[AnotherDilbert]

Less than that required to prevent it flying into orbit with a 1g continuous thrust engine and TL9 control surfaces and flight computer.

Drag at Mach 20 will challenge even the 1 G drives, and the generated heat will threaten to burn the ship up, even with aerodynamic magic.

Not to mention you can use inertia to get above the 1.00g line at which point you can accelerate to orbit anyway.

Yes, so you have to achieve close to escape velocity in the atmosphere, because out of it you will fall quicker than the drive can accelerate you away.

 

[mike wightman]

No, you do not need to be close to escape velocity, you just need to be higher than the 1g line.

And Traveller has magic heat sinks.

 

[AnotherDilbert]

No, you do not need to be close to escape velocity, you just need to be higher than the 1g line.

Escape velocity is lower, it isn't low...

And Traveller has magic heat sinks.

So, you just need magical heat sinks, magical aerodymanics, a thick atmosphere, and Bob's you uncle.

What happens if you run out of magic, or atmosphere? Say, a very thin atmosphere? 100 km runways?

 

[mike wightman]

You use a harder science design system...

Traveller has always been Space Opera trending towards Space Fantasy, the reputation for hard science is based on a lack of blasters and the use of a couple of physics equations.

 

[AnotherDilbert]

Sure, or you use a 2 G drive or don't bother to land on the few planets with high gravity, as you don't need to.

No magic needed...

 

[mike wightman]

You already have a magic maneuver drive, a magic power plant, magic inertial compensators, magic artificial gravity and extra magic heat sinks

and yet having a TL9 continuous 1g thrust reactionless engine, a TL9 streamlined hull with TL9 control surfaces and a TL9 flight control computer being able to fly to orbit is a step too far...

I admit a 1g rocket cannot get to orbit on a size 8-A world, but Traveller ships are not 1g rockets.

 

[kilemall]

One issue for the just park in orbit crowd is the delivery standard is like point to like point. So orbit to orbit or ground to ground.

If one is hardcore about the 1G takeoff limit, then the usual solution would be to only do orbital source.

The trick is D and E starports usually won’t have orbital facilities. This is where the Type R and Type Y small craft makes more flexibility sense and allows the 1G limit to not stop the wings of commerce.

 

[Grav_Moped]

With enough velocity even a BRICK will fly.

The problem here is getting it up to that velocity while it's still on the ground.

 

[Grav_Moped]

Sure, or you use a 2 G drive or don't bother to land on the few planets with high gravity, as you don't need to.

No magic needed...

Or have a 1.25G drive and a bit of patience.
If the rules allow a 1.25G drive, which is part of the problem.

 

[atpollard]

At say 50 km altitude the atmosphere is basically gone, but gravity is still over 99% of surface gravity.

You have to achieve close to orbital velocity IN the atmosphere, because out of the atmosphere is too late, the ship will fall back again.

What's the drag on a Mach 20 brick?

In the Hypersonic regimen (most of orbital flight), gas flow approaches the Newtonian Ideal ... so tilt the nose of that brick up and generate all the lift you will ever need (like a flat plate or your hand out a car window).

Airfoil lift is generally for low speed flight.

 

[AnotherDilbert]

Or have a 1.25G drive and a bit of patience.
If the rules allow a 1.25G drive, which is part of the problem.

Agreed, a 1.4-1.5 G drive would have a sufficient safety margin for most scenarios.
But we only have 1 G and 2 G to choose from, in most editions...

 

[AnotherDilbert]

You already have a magic maneuver drive, a magic power plant, magic inertial compensators, magic artificial gravity and extra magic heat sinks

Yes, we have magical thrust, power, agrav, and heat management mandated by the rules.

and yet having a TL9 continuous 1g thrust reactionless engine, a TL9 streamlined hull with TL9 control surfaces and a TL9 flight control computer being able to fly to orbit is a step too far...

You want to add it because you want all ships to land on all worlds, something the rules does not mandate. You add extra magic, which I find unnecessary.

It would be, dare I say it: A house rule...


In several places, e.g. CT Striker exotic (magical) tech is discussed. Extra magical lift isn't mentioned. It would come in quite handy for hi-performance grav vehicles.

It does say:

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.

 

[AnotherDilbert]

The trick is D and E starports usually won’t have orbital facilities. This is where the Type R and Type Y small craft makes more flexibility sense and allows the 1G limit to not stop the wings of commerce.

The Launch still only has 1 G. If it can land then a Subbie can presumably land too?

The Yacht's 6 G Boat can presumably land just about everywhere.

 

[kilemall]

The Launch still only has 1 G. If it can land then a Subbie can presumably land too?

The Yacht's 6 G Boat can presumably land just about everywhere.

Well pfft I thought it was at least 2G.

It’s not the landing it’s the takeoff. Although for the smaller craft perhaps RATO is possible.

 

[Spinward Flow]

The trick is D and E starports usually won’t have orbital facilities. This is where the Type R and Type Y small craft makes more flexibility sense and allows the 1G limit to not stop the wings of commerce.

This is the argument for containerization of cargo and deployment via small craft to planetary surfaces.

I mean ... if you bring your OWN shuttle service to the party ... then ...

Depending on the overall design specs, you might actually wind up better off with smaller drives and less fuel needed by using a small craft for surface to orbit interfaces, rather than needing to streamline the starship and have more than 1G of maneuver. This is where my broader idea of the LSP Modular Pinnace comes into play for containerized cargo shipping as being a good compromise between staying small and having a good cargo fraction for this kind of "bring your own shuttle" operation.

 

[AnotherDilbert]

It’s not the landing it’s the takeoff. Although for the smaller craft perhaps RATO is possible.

The landing is worse...

If you fall towards the planet at 1.2 G and break with the drive at 1 G, you would be falling with an acceleration of 0.2 G. Faster and faster, until lithobreaking occurs .

 

[Grav_Moped]

The landing is worse...

If you fall towards the planet at 1.2 G and break with the drive at 1 G, you would be falling with an acceleration of 0.2 G. Faster and faster, until lithobreaking occurs .

Unless the interface craft has some aerodynamic lift, in which case you aerobrake, glide, then impact at a couple of m/sec at most above stall speed.

Real-world experience demonstrates that this is a viable approach to EDL (Entry, Descent, and Landing), with a few notable exceptions.

Still leaves the takeoff problem unsolved, though.