To the Moon with the DC-3...
(actually it's just TerraSync being too slow again, but I like it!)
Thorsten wrote in Wed Jul 20, 2016 6:22 am:It's certainly going to need a heat shield for that [...] Thing is - the planet moves around its sun. The sun moves in the galaxy. If your hyperdrive keeps real-space state of motion, the departure and arrival velocity will be very different. The planet also rotates. [...] Also, the atmosphere will (partially) co-rotate with the planet, which will blow you off-track.
Of course you are right, but I think, you make things a little too complicated for what I'm planning to do. Just imagine what would happen to a balloon slowly rising to orbital altitude. It would have a speed relative to the surface dictated by wind speeds. If it rises so far that pressure and wind becomes negligible, it will keep it's last speed (I'm ignoring coriolis effects, but we won't go much higher than 500 km anyhow). So our balloon (or anti-gravity ship) drifts in a known altitude above a known position on the surface, and it has a known speed relative to the surface. It's not orbiting, its simply flying very high, and it is still using a coordinate system relative to the surface with latitude, longitude, and altitude. Arrival from a hyperspace jump would be the the same, but only if our speed is low and not affected by relative speeds of planets, stars, and galaxies.
We don't know how hyperspace drives will work one day (if ever). So we have a certain freedom of defining how they work without having to fear that reality will prove us wrong during our lifetimes.
Science fiction authors have created several methods: superluminal speed (ignoring relativity), warping (made prominent by star trek), jumping/teleporting (like it is done in Elite), natural wormholes, and "star gates" or other kinds of artificial wormholes.
I can't easily say why, but I always preferred the idea of jumping. This method is especially suitable for use in games because you don't have to model a continuous journey through the galaxy, but you can simply load the target planet (or target solar system) while doing the jump. It could even need notable disk loading time without disrupting the game flow, and you don't need visual special effects like wormholes or warp speed effects. Last but not least, you don't need particle deflectors or other fancy stuff to prevent the impact of very-high-speed particles. Jumping keeps our ship as simple as possible and it allows for almost every imaginable outer design. And, as I said, I want to keep the ship as low-tech as possible.
I don't especially like the idea of jumping to a pe-selected absolute position by simply chosing the destination on a map, like it is done in Elite/Oolite. It's ok for a game, but it seems more plausible and flexible (usable in uncharted territory!) to point the nose of the ship in the direction you want to go and jump over a pre-selected distance. Longer journeys could be made by several successive jumps, getting shorter on approach to the target planet. You would certainly need a distance selecting control with a logarithmic scale! This method is similar to how the short range jumps in the original game of Elite worked, that have been replaced by the continous "torus drive" in Oolite which simply increases speed.
Even neighbouring stars can move relative to each other with speeds of more than 100 km/s, and the orbital speed of Earth around the Sun is almost 30 km/s. You would need very strong heat shields to brake from that! Of course we could simply use our fancy thrusters to slow down
outside the atmosphere, but they would have to be very strong, and we would have to do some very critical calculations to not mess up the approach.
But we are doing science-fiction: We can simply define the jump drive to compensate differences in kinetic energy caused by relative speeds of planets, moon and stars - these energies would anyhow be orders of magnitude lower than the energy (probably) needed for the jump itself. So our ship jumps to a position with a speed of 0 relative to the centre of the
gravitationally dominating object, i.e. the star, planet, or moon the ship will fall to if we don't prevent it. We could make it a little more realistic and calculate interpolated speeds for positions in between two or more objects (e.g. L1), but at these locations there is nothing to see, and we wouldn't notice slightly "wrong" speeds. After all, we don't even have a working speed indicator outside an atmosphere! We would just make a short jump nearer to the object we intend to land on.
For landing we would have to accelerate to the rotational speed of the planet (not to much higher orbital speeds). For Earth, this speed is about 465 m/s or 1674 km/h (40000km/86400s) on the surface, and only a little more at 200 km altitude. FG can't do it (yet?) but if it was possible to jump from somewhere to Earth, the simulator would have to give our ship the rotational speed in a westerly direction, of course depending from latitude and altitude. It isn't a very high speed: Every modern fighter can do this, and for our space ship it would be no problem at all: While descending slowly into the denser parts of the atmosphere, the air resistance would accelerate us very gently (or brake us from the flight simulator point-of-view). I assume, FG would do this without additional code because it should treat the space ship like an airship flying at a very high altitude.
Orbiting is something completely different of course, but a ship equipped with the technology I imagine wouldn't need to do it, and it wouldn't need the computers and precise maneuvering needed for orbiting. It wouldn't even need to be able to accelerate to supersonic speeds, and the main thrusters would mostly be needed only for atmospheric flight. A ship like this could and should able to be flown "by feeling"; the only critical thing (apart from interstellar navigation
) would be to prevent too high speeds during the approach. Testing my ship will prove me right or wrong, but test flying will be one of the interesting parts!
[Antigravity] would depend on whether is is some force countering gravity or whether it is inertia suppression - the two are rather different.
I'm thinking about countering gravity, like some magnetic or electrostatic effect, not about simply reducing mass to make the ship "invisible" for gravity. It is science-fiction of course, but I want it to be plausible. The ship creates its own gravity field "somehow" (I wish I would know how to do it!
). In outer space it could perhaps even be used as artificial gravity, so you can walk around in the ship, but that's not important for FG. Near a planet, the artificial field interacts with the surrounding field. If the gravity devices are creating 9.81 m/s², the ship will float stationary above the surface. If they create 5 m/s², it would fall as if Earth's gravity would only be 4,81 m/s², and if they create 10 m/s², the ship would rise with 0.19 m/s² (if we ignore air resistance). And if the ship rolls or pitches to 90°, the antigravity effect would be zero, the ship would fall like a stone. At least, that's my rough plan at the moment...