If you can accelerate or decelerate outside the atmosphere then the atmospheric friction problem is a non-issue. The propulsion mechanisms in Traveller allow this. An unpowered re-entry (of the sort done by contemporary spacecraft today) uses atmospheric friction, which is very hard on the craft - so much so that the craft is generally viewed as a one-shot item or in need of substantial refurbishment work afterwards.
Orbital velocity for earth is about 7km/sec, which will generate very intense friction heating (technically compression but I digress) if you re-enter the atmosphere at that speed. A Powered re-entry where you use a manoeuvre drive to slow down (to perhaps 1-2km/sec) means that you can enter the atmosphere at speeds where the atmospheric heating will be much less intense. This will be far easier on the hull. It could reasonably be inferred that a suitably equipped grav vehicle could do this.
Orbital velocity for earth is about 7km/sec, which will generate very intense friction heating (technically compression but I digress) if you re-enter the atmosphere at that speed. A Powered re-entry where you use a manoeuvre drive to slow down (to perhaps 1-2km/sec) means that you can enter the atmosphere at speeds where the atmospheric heating will be much less intense. This will be far easier on the hull. It could reasonably be inferred that a suitably equipped grav vehicle could do this.
Or by any reasonable Traveller TL (say 10+), a modern ablative expanding foam heat shield (like the Gemini skydiving from orbit concept) might be available as a can of single use spray on foam.
[My father was a research chemist - retired now - and developed a foam in the 1980's that expanded to provide fire protection for wood ... the hotter it got, the more it expanded and the greater the thermal insulation it provided.]
[My father was a research chemist - retired now - and developed a foam in the 1980's that expanded to provide fire protection for wood ... the hotter it got, the more it expanded and the greater the thermal insulation it provided.]
Reynard
Emperor Mongoose
What I always assumed from those years of Traveller description was a Traveller starship or spaceship had gravitic capability just like non-ship vehicles but vastly more powerful and that meant planetary flight at all speeds as a VTOL craft. Grav vehicles just don't have the power to burn themselves in an atmosphere unless they free-fall in a suitably thick one. Unless you lose power and/or control, your landings should be no issue. This is why we don't see ships or vehicles using any protective means beyond something akin to an airplane.
Condottiere
Emperor Mongoose
https://www.youtube.com/watch?v=DWMPe3wF9jQ
Condottiere
Emperor Mongoose
It's a controlled fall, whereas with the shuttle it's a controlled crash.
I'd only require a roll to determine how bumpy the ride was or under bad conditions (if the ship or grav vehicle is damaged, landing in the middle of a hurricane, or something similarly problematic). Between even the most basic automation (I'm assuming that TL 10+ vehicles have automation at least as good as we have on commercial airliners) and a reactionless grav-based drive, landing for orbit would be easy, assuming that nothing else is going on.dragoner said:
dragoner said:
Beyond my own personal feeling that RPG systems (and GMs) make players make entirely too many skill checks for things, there are several descriptions in various editions of Traveller that say that it is pretty common for Air/Rafts to be used as a kind of excursion vehicle from an orbiting starship to ground and back again. If the Air/Raft doesn't have a pressurized cabin attachment/a pressurized cabin model (depending on edition of the game and model), the passengers will have to wear pressure suits, but otherwise it's not unheard of for Air/Rafts to shuttle in and out of orbit.
With that in mind, I wouldn't even give it a pilot roll. As grav vehicles don't really depend on aerodynamic lift at all, they don't require such surfaces, nor are they constrained by stall speeds and so on. If the maximum safe re-entry speed is 50kph, the Air/Raft slowly descends at 50kph, more than slow enough to not worry about re-entry heat and a TL12+ Air/Raft would have sufficiently good computers to control the gravitics that stability wouldn't be an issue. Safe, but slow (and therefore a boring trip).
Now, if the driver of the Air/Raft wants to come screaming in with speed warning wailing away and danger lights blinking on the console like Christmas tree lights, yeah, that's piloting roll time. 8)
There is a balance between too many skill checks and not enough, the check for an air/raft pilot skill entering an atmosphere, it's hours long, and provides for some chance of excitement. I'm not sure if I'd call it totally mundane; for example, I could drive my car down to Central or South America, taking a plane is easier by far. The adventurers would probably drive the car though.
It all depends on the situation. I tend to sympathise with Dragoner's take. Too many GMs ask for rolls to try to inject interest in fundamentally uninteresting activities. What is at risk? What are the consequences of success or failure? If the players botch it badly, not an unlikely outcome on a 2D6 roll if such an outcome is possible, is that going to be interesting?
For a familiar world the characters have visited before, for a routine landing no check required. For an unfamiliar world with a Class B+ Starport, and therefore decent air traffic control and weather warnings, etc also no roll except in unusual circumstances.
On an unfamiliar world with Class C- Starport I'd ask for a roll to land at a designated spot on the basis they won't be familiar with things like the planet's rotation rate, atmospheric pressure gradient, air currents, etc. If they don't care where they land, I'd be more lenient, but the consequences of a failed roll are mostly just going to be more time taken. If that's not an issue, a roll is superfluous.
Simon Hibbs
For a familiar world the characters have visited before, for a routine landing no check required. For an unfamiliar world with a Class B+ Starport, and therefore decent air traffic control and weather warnings, etc also no roll except in unusual circumstances.
On an unfamiliar world with Class C- Starport I'd ask for a roll to land at a designated spot on the basis they won't be familiar with things like the planet's rotation rate, atmospheric pressure gradient, air currents, etc. If they don't care where they land, I'd be more lenient, but the consequences of a failed roll are mostly just going to be more time taken. If that's not an issue, a roll is superfluous.
Simon Hibbs
GypsyComet
Emperor Mongoose
F33D said:
As long as the grav vehicle can handle the high altitude wind velocity *changes* in stride, it will even be an easy trip. Those changes are why I wouldn't recommend such a trip in a standard "country truck/barge" Air Raft. They just aren't fast or responsive enough to keep it from being a wild ride.
GypsyComet said:
How to explain this simply... You don't feel them as you fall as you move with the column of air. That is why the person could parachute from space. The jet stream is the fastest wind and it is not a wall of fast moving air next to motionless air. It is a gradual change of velocity with the fastest air at the center. The craft (or a person) doesn't notice. This is also why very fragile (relatively speaking) WW2 era planes were not damaged by flying at stratospheric altitudes by those winds.
GypsyComet
Emperor Mongoose
F33D said:
My point is that a vehicle with very little aerodynamic thought in its design that tops out at 60mph is not going to have an easy time, while something with a faster top speed (which includes all those WWII bombers) and some consideration for aerodynamics is going to have it much easier. Being able to match velocities easily is vital to the trip not turning into the longest case of air sickness you never wanted.
EDIT: It should be noted that the MGT version of the Air-Raft is much faster than the vehicle under that name in every other edition. It is still open-topped, though. Wear your seat-belts.
GypsyComet said:
Not a problem. The human body is only spec'ed to ~20 mph and it handles 10X that in free fall no problem. Also, you don't really understand how it works. The body in motion slowly gets moved up to the speed of the air mass. SO, you are confusing ground speed with air speed. THAT is the reason that the WW2 craft didn't have a problem. Are you a pilot?
GypsyComet
Emperor Mongoose
F33D said:
Yes, and that is precisely the problem. Until the air-raft has matched the air mass velocity by whatever means, it is not in calm air, is shaped like an angular bathtub, and has very few tools to usefully interact with the air in that interval. Grav vehicles fly despite the air, not because of it. They are interacting with the gravity of the world in order to fly.
The caveat of the Mongoose version of the Air Raft is that stated speed. In order to achieve that speed it must be better suited to travel through air. Whether this is due to a more aerodynamic shape or some trickery with the gravitic field is not stated, but 400kph in an open-topped vehicle is going to need something. Whatever it turns out to be, the Mongoose Air-Raft a) probably needs a different name, and b) should handle re-entry or a lift to orbit much more easily than the pokey 100kph Air-Raft of other editions.
GypsyComet said:
It matches it gradually as it enters it. At orbital altitude the density is so low it has no adverse effect. AGAIN, see what happened to the parachute person. So, as demonstrated, no problem. :shock:
n.b. - an aircraft has MUCH more surface area (that sticks into the air flow) than the body of an air raft. If you were really a skilled pilot you would have remembered that.
