[HG 2e] Aerofins and streamlining

[AnotherDilbert]

If you jump off the Empire State building, all things being equal, you go straight down.

"straight down" is a very relative concept in a rotating system.

As soon as you step off the building you are technically in orbit around the Earth, though a highly elliptical orbit intersecting the Earth. Falling ~400 m at about 50 m/s would take in the region of 8 s. The surface of the Earth is moving sideways at about 465 m/s, but so are you since the top of the building has slightly higher speed than the ground. As soon as you step off the building the sideways speeds will start to diverge. You will hit the ground clearly displaced to the side of where you stepped off the building.

The simple answer is that you never fall "straight down" on a rotating planet.

 

[Nobby-W]

If you jump off the Empire State building, all things being equal, you go straight down.

So at what altitude in the atmosphere would that happen with a spaceship?

I think we're back to not understanding orbital mechanics, but I can't tell if you really don't get this or you're just trolling. I've provided a link to an introductory article on the subject below. For a bit more of a practical approach I will re-iterate my previous suggestion to learn to play Kerbal Space Programme.

https://en.wikipedia.org/wiki/Orbital_mechanics

https://en.wikipedia.org/wiki/Rotating_reference_frame

The empire state building is sitting on the ground, moving at the same speed as the ground, which is considerably less than orbital velocity. If you jump off it you will fall nearly straight down with respect to a rotating frame of reference, but you're actually travelling at several hundred m/sec horizontally. If you have a space station in orbit, then it's travelling at several km/sec horizontally. If you try to jump off it you will remain in orbit. In order to fall you would have to slow your horizontal velocity to zero or near enough to zero so that you fall. Technically this means that you have changed your orbit enough so that its periapsis is under the surface of the world, an activity sometimes referred to as lithobraking.

 

[Condottiere]

So going straight down is illusionary, and requires forward velocity or momentum to compensate for that drift, not taking into account wind speed and direction.

The question of course is, expressing the actual speed of that forward momentum into something that anyone can understand, which would also have to take into account the speed and/or time spent descending, since the faster you go down, the less forward momentum you'd need.

The same could be said of going straight up: you'd have to angle the ascent of the spacecraft.

If you turn on the gravitational motors, it anchors itself on the local gravitational field. Instead of rejecting gravity, on one plane it would welcome it, and goes straight towards the centre of the field. Plus compensating for wind and the requisite forward momentum.

 

[Reynard]

To the original question, "The question is, are you all happy with aerofins on a partially streamlined hull?", the HG2e rules allow any configuration to have them. What is most important are the Atmospheric Operation rules on page 143 in the core book. Streamlined is inherently optimized by shape and features for atmospheres and difficult weather conditions. Partial streamline has surfaces and structure that make it cost effective in their normal environment outside an atmosphere but become destabilizing with the chaos of weather. Unstreamlined is optimizing the shape and space for maximum cost effect but is meant for microgravity so it's structurally fragile and not featuring landing equipment or shaped to land hence the damage taken as your ship is shaking and breaking up. The AG or contra-grav built it is probably the only thing preventing total wipeout.

Aerofins give each configuration an edge, even the unstreamlined, but aerofins on unstreamilned is lipstick on a pig. The vast majority if the time it makes no sense in the first place. Partial at least has a fighting chance.

Also remember, "A ship with aerofins deployed gains DM+2 to *all* Pilot checks when within an Atmosphere.". That means a ship in an atmosphere with aerofins outclasses a ship without aerofins for any Pilot Task such as engaging in combat in an atmosphere or attempting maneuvers or stunts.

 

[Nobby-W]

[ . . . ]
The question of course is, expressing the actual speed of that forward momentum into something that anyone can understand,

Or, maybe, you know, doing some actual reading on the subject and putting some thought into your position before you start posting.

 

[edpovi]

To the original question: aerofins do make the most sense on a streamlined ship as you are using lift for flight and control at that point.

On the side question, with the technology Traveller, a ship can do 1+ G thrust with their drives. This would allow for a powered decent from space, basically just "float" down from space. The "Karman Line" for earth is just 62 miles / 100 km, not that far to go when you have a reaction-less "Maneuver-Drive" with endurance measured in months.

But this is also a game where you don't really need to know physics || orbital mechanics || KSP to play...

 

[Condottiere]

That's why I like tables, since I'm not an engineer.

The rules allow you to overclock the drives, though realistically I would have thought in terms of percentages, rather than plus one gee.

Booster rockets might be an option.

 

[Reynard]

Booster rockets are soooo reaction drive, so last tech level!

 

[Condottiere]

https://www.youtube.com/watch?v=u7LMlr9cWO4

 

[Reynard]

Back when that show was on tv, I had XL-5. It was about 3-4 feet long. The front cockpit detached and the window could be removed to get to the bridge area for the figures of the crew. Side hatches allowed access all over the ship.

*sigh* I miss it.

 

[Condottiere]

I like to think the current Thunderbirds is a tolerable reboot.