1g Ships and Size:7 worlds...

[Captain_Ahab]

I worked out aerodynamics once
I can clean up my notes, if anyone is interested

density relies on pressure, composition, and temperature, which Trav's UWP really doesn't get much into
frontal area is relatively easy for people to find
Cd can be estimated from generally streamlining in RAW and the ship's fineness
Thrust is known or easily figured

just figure the velocity where thrust is equal to drag for the max speed in an atmosphere of the density at the desired altitude
then work out stagnation temps and skin temps from radiative heat transfer
I just assume the shockwave has a temp near stagnation, so everything must be inside the shock cone

or just go with whatever the plot needs

tinkering can be fun, but if it affects speed and simplicity at the game table, it is best to ignore it

 

[AnotherDilbert]

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).

OK, what does that do to drag and heat buildup at Mach 20?

 

[AnotherDilbert]

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.

VTOL, on a rocky field someone optimistically called a E port?

What's the stall speed of a brick?

At least the Subbie Launch is better than the cylindrical default Launch?

 

[Grav_Moped]

VTOL, on a rocky field someone optimistically called a E port?

What's the stall speed of a brick?

At least the Subbie Launch is better than the cylindrical default Launch?
View attachment 3523

You're going to need some ground infrastructure to pull it off -- if only a vast dry lakebed.

Yeah, that launch ain't gonna glide all that well without invoking the Rule of Cool.

The Subbie's at least got a lampshade for the problem (it has wings -- don't ask about the L/D, CL_max, or wing loading though).

 

[AnotherDilbert]

What's the stall speed of a brick?

The Shuttle landed at about 350 km/h, a wingless spacecraft is presumably worse?
Do we want to touch down at 500+ km/h, even with a decent runway?

 

[AnotherDilbert]

The Subbie's at least got a lampshade for the problem (it has wings -- don't ask about the L/D, CL_max, or wing loading though).

I don't think we need to overthink the shape and size of the wings in illustrations. It has wings and plenty of power, presumably good enough for routine flight.

Wingless craft, I'm not so convinced...

 

[Grav_Moped]

The Shuttle landed at about 350 km/h, a wingless spacecraft is presumably worse?
Do we want to touch down at 500+ km/h, even with a decent runway?

Can the thrust from the main drive be vectored, so the maximum sink rate is 2m/sec² and at touchdown use the drives as thrust reversers?

You'd have to nail the timing and land at just about stalled. And, with typical Traveller ships, it's not going to work -- if only because there's nothing holding the nose up after the stall.

Again, either there's a Rule of Cool carveout to aerodynamics, or it can't work for most 1G ships as drawn for Traveller.

There are configurations that could work. Those configurations are not those typically used for Traveller starships.

 

[AnotherDilbert]

Let's see:

Land at 200 m/s (brick?), break at ~2 m/s2 (shuttle), it stops after 100 s using 100 m/s * 100 s = 10 000 m = 10 km runway.

What do we need for safety margin? A factor of two? So, a 20 km runway?

 

[Grav_Moped]

I don't think we need to overthink the shape and size of the wings in illustrations. It has wings and plenty of power, presumably good enough for routine flight.

Wingless craft, I'm not so convinced...

Dat phat trailing edge tho.

 

[AnotherDilbert]

Can the thrust from the main drive be vectored, so the maximum sink rate is 2m/sec² and at touchdown use the drives as thrust reversers?

Undefined in CT, limited vectoring in MT.

Again, either there's a Rule of Cool carveout to aerodynamics, or it can't work for most 1G ships as drawn for Traveller.

We can technobabble it if we want to, I just don't want to...

I don't think we need it, and I like having a bit of terrain interfering: No, you can't land because...

 

[Grav_Moped]

Undefined in CT, limited vectoring in MT.



We can technobabble it if we want to, I just don't want to...

I don't think we need it, and I like having a bit of terrain interfering: No, you can't land because...

It comes down to the same thing it's always been, since '77: either ignore the issue (they're streamlined so they can fly, so it works and don't sweat the details) or just say no. I'm ok with either answer. Depends on the feel you want for the campaign.

 

[AnotherDilbert]

It comes down to the same thing it's always been, since '77: either ignore the issue (they're streamlined so they can fly, so it works and don't sweat the details) or just say no. I'm ok with either answer. Depends on the feel you want for the campaign.

Of course your TU works just like you want it to, it just isn't the Traveller rules that made you do it that way.


I think most of the discussions are because we all read the LBBs 40-45 years ago, misunderstood some, changed some, added some, forgot most of that, and now we are arguing about our vague recollections.

 

[AnotherDilbert]

Dat phat trailing edge tho.

Artistic license? It's a hand-drawn illustration, not an engineering schematic.

 

[Grav_Moped]

Of course your TU works just like you want it to, it just isn't the Traveller rules that made you do it that way.


I think most of the discussions are because we all read the LBBs 40-45 years ago, misunderstood some, changed some, added some, forgot most of that, and now we are arguing about our vague recollections.

Not going to argue that point.

I will say that it's enlightening to look over the rules to figure out how they did it the first time, and why they made the choices they did.

 

[Grav_Moped]

Artistic license? It's a hand-drawn illustration, not an engineering schematic.

It's both.

The artistic license is that despite not being actually all that aerodynamic, it gets treated that way in-game because it looks cool. And, to be fair, it'd look kind of alien and unworkable if it were drawn in a form-follows-function style.

 

[Condottiere]

While with spaceports it might not matter, you'd think that spacecraft would have to be certified to land at an Imperium starport.

 

[Grav_Moped]

While with spaceports it might not matter, you'd think that spacecraft would have to be certified to land at an Imperium starport.

You'd think that. Most of the time, you'd be right.

 

[Condottiere]

It's Imperium territory, run by bureaucrats.

If it crashes, there would be an investigation, especially if the spacecraft damages infrastructure or people are killed.

 

[atpollard]

Do we want to touch down at 500+ km/h, even with a decent runway?

FYI:
500 kph landing speed and 1G (10m/s) deceleration = 964 m landing distance ... about a 2 km runway.
1000 kph landing speed and 1G (10m/s) deceleration = 3.85 km landing distance ... about an 8 km runway.
The Space Shuttle Runways (plural) at White Sands, NM are each 11 km long.

[shrug] so it CAN be done ... even at Class E

[EDIT] now, a Mach 5 [hypersonic] takeoff speed of 6174 kph and 1G (10m/s) acceleration = 147 km takeoff distance ... a 150+ km runway ... so that may be trickier to build ... but a 4G "launch sled" could reach that velocity in only 37 km. [or 11 km @ 14G for 12 seconds ]

 

[kilemall]

So Type E at 1G planets are either salt flats or water landing?