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Forum » SpaceEngine » Gameplay Discussions » Spaceflight Physics Concept (A Concept Prototype)
Spaceflight Physics Concept
SpaceEngineerDate: Sunday, 18.12.2011, 11:36 | Message # 1
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The Mothership

More information about the design of the ship - in Mothership concept thread.

1) Subluminal engines

The ship will use rocket engines, but not chemical propulsion. So the source of energy and reactive mass (the working substance or propellant) are different things. For example, the propulsion substance is hydrogen, which is accelerated by an electromagnetic field (plasma engine or beam engine). The energy for the field comes from a separate power unit (the reactor).

The propulsion engines are very powerful and have a high exhaust velocity, they can speed up the ship at 10-20 G acceleration, and a ship has a characteristic speed velocity of up to 10,000 km/s from one refueling. The characteristic speed or deltaV is the total ability to change its speed. For example, deltaV = 10,000 km/s means that ship can be accelerated 10 times to 500 km/s and break down. Such a large delta-V will have the most advanced ships in the game. The propulsion substance for the engines is hydrogen, water or something else, that can be easily mined from space.

Refueling with hydrogen can be carried out during the flight through the atmosphere of the gas giant. The ship flies close to the gas giant at a certain speed, the air intake (ram scoop) opens in upper atmosphere and fills the tank. A more profitable refueling can be done with the low-mass gas giants such as Neptune (they are called ice giants): and they have a lower escape velocity, so a ship spends less hydrogen when departing from it. Another option is to produce hydrogen from water or ice, which may be found on icy satellites or in comets.

Hydrogen in its liquid and solid phase has a very small density, so it needs a huge tank. For example, one of the calculations (see below), will need a tank diameter of 1,200 kilometers, or 200 tanks with a diameter of 200 meters. Therefore, the game will use technology to store hydrogen in the so-called degenerate ("metallic") state, as in the depths of gas giants. The density of hydrogen in this state is comparable to the density of water, and the diameter of the tank is reduced to 460m, or 12 tanks with a diameter of 200 meters.

Example calculation of mass and kinetic characteristics of the ship:

  • Size: diameter 400 m, length 1500 m
  • Mass without hydrogen: 1.5x1011 kg
  • Hydrogen mass: 6.0x1010 kg
  • Acceleration: 50 m/s2
  • Thrust: 7.5x1012 N
  • The characteristic velocity: 10 000 km/s
  • The exhaust velocity of hydrogen: 30 000 km/s
  • Hydrogen flow rate: 251 000 kg/s
  • The time of complete consumption of hydrogen: 2.7 days
  • The density of liquid hydrogen: 70 kg/m3
  • The diameter of the tank for liquid hydrogen: 1200 m (or 203 tank with a diameter of 200 m)
  • The density of metallic hydrogen: 1150 kg/m3
  • The diameter of the tank to metallic hydrogen: 460 m (or 12 tanks with a diameter of 200 m)


2) Superluminal engine

There are two concepts for superluminal (faster-than-light) engine: "hyperaccelerator" and "series-jump drive". Technically, the FTL drive will be implemented as acceleration of timerate in physics simulation for the ship, but not for the planets and other objects in game. One can imagine hyperflight as an ordinary subluminal flight working within the laws of celestial mechanics, but with time accelerated. It saves the ship's energy and momentum.

The first concept is easy to understand, but it still requires more of a "physical explanation". Suppose, for example, one took a flight from Earth to Mars. The ship or player calculates the transition orbit; the moment of engaging and disengaging of the main rocket engines. Once the ship reaches the engagement point, it accelerates to its preset travel speed using main engines. Then the ship flies by inertia and reaches Mars within several months. But instead of doing this, the ship turns the hyperaccelerator on. It seems like the time-flow is sped-up a few million times for the ship: it reaches Mars within a few seconds. When the ship reaches the breaking point close toMars, the hyperaccelerator is switched off, and the ship then disengages its main engines and enters Mars' orbit.

The second concept is a "series-jump drive." It allows the ship to perform instant teleporting over some distance ("hyperjump"). But the ship cannot perform a single jump within a light-year distance. Instead, the ship makes a series of short frequent jumps at millions or billions of kilometers. After the jump, the jump-drive recharges its capacitors over time for about 1 millisecond. To the pilot, the superluminal flight looks like continuous (because of the 1000 jumps per second) superluminal motion with no relativistic distortions (because the actual physical speed of the ship can be at least zero). So, it works like interstellar flight as it is in SE now. Large ships can have less time between jumps, or can perform a series of jumps with greater frequency to obtain greater "hypervelocity".

The time acceleration factor (for the first concept) or distance of a jump (for the second concept) is affected by local gravitational fields. Therefore, when approaching a planet or a star, the ship will reduce its "hypervelocity". Travel inside a planetary system is slower than interstellar travel, and interstellar flight at the galaxy's core is slower than at the galaxy's perimeter.

The ship cannot perform hyperflight from the surface of the planet to its orbit or jump far away into space: It must accelerate to at least the escape velocity of the planet. Energy must be conserved, and during flight it should not be less than the potential energy required to exit the initial gravitational field of the planet. The calculation of the hyperflight should take into account the relative velocity of the departure point and destination point - it consists of the velocities of the ship, planets, and stars. The calculation should also consider the gravity field potential: The sum potential of all the planets and suns in the system (it is easy to do), and the potential of the neighbouring stars and of the galaxy (in case of interstellar flight).

In summary, to perform the hyperflight, the ship should be accelerated to escape velocity to leave a planet or star's gravitational field, and to compensate for the speed difference between the departure and destination planet/star. So, flying to nearby stars require about 30 km/sec, to accelerate the ship with 10 G acceleration would take 5-minutes. The hyper-flight itself takes only a few seconds or minutes. A trip to the other side of the galaxy requires about 500 km/s, as the velocity of stars around the galactic center is about 250 km/sec. This means that a flight will take much time and may require refueling of propellant (hydrogen), at some time during the trip. A flight to a distant galaxy would take hours or even days, because the ship will have to compensate for the Hubble velocity of the galaxy, and this is done only with rocket engines. If the characteristic speed of the ship is 1000 km/s, and the destination galaxy is moving away from the departure galaxy at a speed of 10,000 km/s, One would have to make ten intermediate stops at some galaxies along the way for each refueling - this is only way to reach a speed of 10,000 km/sec for this type of ship.

3) The energy generator

Subluminal and superluminal engines use energy (e.g. electricity) from the main generator ("core"). The proposed core is to be a "vacuum energy converter" or "zero point module". In this case it can be combined with superluminal engine in a single device. Another technology for the core is a fusion or antimatter reactor which can be combined with sub-light (main) engines.

The "series-jump" concept of hyperdrive needs a huge battery energy storage device (such as quantum capacitors) located next to the hyperdrive. These capacitors are needed to power the hyperdrive, because it is "jumping", and therefore consumes great power to make one jump that the main energy generator ("core") can't generate. The further the jump, the more energy and time one needs to charge the capacitors. A vacuum energy generator drains energy from the vacuum around it, the energy density in space falls down, and organizes the flow of energy from the surrounding areas of the generator. Therefore, in the first moments the core gives more power, which gradually decreases and stabilizes at a certainlevel, such as 1% of the maximum level. But when the ship jumps away, it finds itself in a"fresh" area of the vacuum, where the core may reach the maximum power output again. Therefore, it is more efficient and faster to make a series of short jumps, rather than making one long jump.
 
SpaceEngineerDate: Sunday, 18.12.2011, 11:41 | Message # 2
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The Shuttle

The shuttle is designed to land on planets with atmospheres. It's equipped with thermal rocket engines for flight in a vacuum and has a Ramjet/Scramjet engine for atmospheric flight. The ship uses air from a planet's atmosphere in atmospheric flight mode, and a working substance (hydrogen) from the on-board tank in space flight mode. The energy generator is the same as the Mothership's; it generates electricity to power the engines. The shuttle can use some other working substance instead of hydrogen, including the air from an atmosphere. The shuttle dos not havea hyperdrive for space travel.

There are two variants of shuttle design: an aircraft-type (for horizontal landing using aerodynamics) and a rocket-type (for vertical landing on its tail, as classic sci-fi rocket ships do).

The shuttles that are designed to land on airless bodies only, have a rocket design. However, they may be much lighter than atmospheric shuttles, because airless bodies usually have a low gravity. They also do not require a aerodynamic shape. Atmospheric shuttles can land on airless bodies too, if their rockets engines allow for it (Ramjet engines cannot be used on airless bodies).

Aircraft design

The shuttle has an aircraft form (similar to the US Space Shuttle): a horizontal design, with wings to create aerodynamic lift, with jet engines at the rear of the chassis and Ramjet engines on the wings or at the bottom.

  • Take off. The ship is launched from the surface in several ways: for example, using small thrusters for vertical take-off, or for rotating of the main engines. It will then engage the Ramjet engines, gaining speed and altitude. The Ramjet engines use air as the reactive mass without spending hydrogen from the tanks. In the upper atmosphere, where the velocity reaches 10-20% of the orbital velocity, the rocket engines engage, and the ship reaches orbital velocity. The rocket engines will use plenty of hydrogen stored in its tanks in its metallic form. On approaching the mother-ship, the shuttle will make basic maneuvers to intercept and dock with it.From launch to orbit takes 5-10 minutes (while accelerating at 2-3 g), but the basic intercept maneuver may require a few hours and several orbital turns. Therefore, the Mothership can adjust its own orbit, and use a hyperdrive to make a quick flight tomeet with the shuttle.

  • Landing. The ship slows down its orbital velocity by using its jet engines, it then enters the atmosphere at an acute angle. The descent flight through the atmosphere happens at hyper-sonic speed, resulting in the ship heating up, caused by air friction. The heat-shield at the bottom of the shuttle protects it from over-heating. The shuttle reduces its speed with air friction, to increase its efficiency, the shuttle can fly in wave-like motions, moving from left to right. When the speed drops below several times the speed of sound, the Ramjet engines engage and the remainingflight to the landing zone is done in aircraft flightmode. Landing can be carried out either by vertical take-off thrusters or turning main engine thrusters to 90 degrees towards ground.

  • Benefits. The use of Ramjet engines reduces the weight of the ship and the amount of hydrogen required for take-off. Flight in the atmosphere in aircraft mode does not consume hydrogen and is not limited by distance.

  • Weaknesses. Acceleration during take-off and orbital flight is directed "back" (toward the engines), but during landing, atmospheric flight and when parked on the surface, it is directed "down" (toward the ship's bottom). So it requires special internal planning. Braking while landing is aerodynamic, which leads to dangerous over-heating, and a large distortion of the hull can destroy the ship. Take-off and landing without a runway is only possible by special vertical take-off engines or by rotating main engine thrusters (more mechanical modules reduces reliability).

    Rocket design

    The shuttle is of rocket form. It has a vertical design, with aero-stabilizers at the bottom with jet engine/s mounted on them. Stabilizers can also be used as landing supports.

  • Take off. Is carried outvertically, the same as a conventional rocket. In the initial stages of flight, the ship may use Ramjets engines and save itself hydrogen consumption. Upon reaching the upper atmosphere, this ship will make a course correction, with its flight path becoming more horizontal. From this position, the jet engines will engage.

  • Landing. In contrast to the aircraft-design version, this shuttle will not use aerodynamic braking, its landing will be like launching, but in reverse. The ship breaks its orbital speed and enters the atmosphere with its tail forward, slowing itself down with its jet engines at a relatively low speed, then gently lowers itself to the surface until finally sitting tail down on the ground. The jet engines are still working during the landing phase, so the ship must carry a greater amount of hydrogen, compared to the aircraft-design version.

  • Benefits. Acceleration at all stages is always directed "downwards" (towards engines) - ideal for carrying passengers. The hull does not overheat during landing. Landing can be done on any solid surface. The hull design is monolithic with no moving parts (except for operating on the landing supports), which improves its reliability. It can land and take off from any planetary bodies - with or without an atmosphere.

  • Weaknesses. It requires a greater amount of hydrogen in its on-board tanks, as compared with the aircraft-design version. Atmospheric maneuvers are limited, because flight is only possible in rocket mode, which consumes hydrogen.




  •  
    AlphaDate: Sunday, 18.12.2011, 12:06 | Message # 3
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    Will you take in account the UFO phenomena in your ships propulsion system?
     
    curiousepicDate: Sunday, 18.12.2011, 19:21 | Message # 4
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    I like the "hyperaccelerator" time compression version of the FTL drive. It could be very much like the current "go to" command, because it would smoothly accelerate and then decelerate as you move away from and towards higher gravity fields. Also, if you pass nearby another star that's on the way to your destination (perhaps an unseen brown dwarf or planemo), your speed would automatically slow down, giving you time to take a look at it as you go by, and perhaps do a brief scan for planets, etc.

    As I mentioned in the mothership thread, this also somewhat resolves my issues with FTL communication. Time is "conserved", players are essentially on the same timeline, and don't experience any relativistic time dialation.

    As I also mentioned, this also means the player character would have to go into cryosleep during each jump, but now I have a better idea: some sort of reduced metabolism, so that they experience the world at a slower rate subjectively, but it essentially matches the real player's speed of thought and action.

    I also propose that the "core" be based on an artificial black hole, since they are tied to forward time travel concepts.





    My ideal preferences for visual design of the mothership and technology in SE
    Harry Potter and the Methods of Rationality


    Edited by curiousepic - Sunday, 18.12.2011, 20:02
     
    SpaceEngineerDate: Sunday, 18.12.2011, 23:57 | Message # 5
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    Quote (Alpha)
    Will you take in account the UFO phenomena in your ships propulsion system?

    No smile

    Quote (curiousepic)
    As I also mentioned, this also means the player character would have to go into cryosleep during each jump

    Why? All players will play in real time, no matter in hyperflight for them or not. That is hyperflight physics.

    Quote (curiousepic)
    I also propose that the "core" be based on an artificial black hole, since they are tied to forward time travel concepts.

    No, it is bad, because spaceship should have a low mass as possible. A black hole in thousands of tons of unnecessary mass.
    BTW, main rocket engines may be built based upon a black hole too.

    *





     
    curiousepicDate: Monday, 19.12.2011, 02:54 | Message # 6
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    Quote (SpaceEngineer)
    Why? All players will play in real time, no matter in hyperflight for them or not. That is hyperflight physics.

    Then perhaps I misunderstand the concept. Here is my understanding:

    The hyperaccelerator creates a bubble around the ship within which time passes more quickly than outside the bubble. This would mean that, for someone outside the bubble, light appears to travel faster inside the bubble. And because the bubble is produced by the ship, and the ship is moving in space, the ship itself can travel faster than light, relative to the stars. (I'm aware this might not actually make physical sense, but that's why we're inventing the FTL drive).

    However, this means that more time passes inside the bubble than outside. The Player Character (and the player) would want this time to pass more quickly, hence the need for cryosleep, or my suggestion of a slower metabolic rate, which would make the player's thoughts the same speed as someone outside the bubble.

    One reason I thought this was the case is because with any other FTL scheme, you run into the problem of relativistic time dialation. If Player A leaves the home planet of another Player B, and travels near or faster than the speed of light to another star, and then returns, relativity says that Player B experiences much more subjective time than Player A. My understanding of the hyperaccelerator, plus the slow metabolism, would get around this issue and provide justification for why every player retains a constant passage of time.

    Quote (SpaceEngineer)
    No, it is bad, because spaceship should have as low a mass as possible. A black hole in thousands of tons of unnecessary mass.


    Micro black holes can (theoretially) be any mass. Also, I envision the black hole itself being what "pushes" the ship during FTL, such that the mass of the black hole itself doesn't need to be taken into account. Anyhow, it was just a random idea, not really thought through.

    Quote (SpaceEngineer)
    BTW, main rocket engines may be built based upon a black hole too.

    Huh? This seems to contradict saying that they're too massive for the ship. There are a few concepts for using a mini-black hole for normal sub-light propulsion of a ship though, is that what you're referring to?





    My ideal preferences for visual design of the mothership and technology in SE
    Harry Potter and the Methods of Rationality


    Edited by curiousepic - Monday, 19.12.2011, 02:59
     
    SpaceEngineerDate: Monday, 19.12.2011, 10:36 | Message # 7
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    Quote (curiousepic)
    Then perhaps I misunderstand the concept. Here is my understanding:

    I don't work on physical explanation of how hyperaccelerator works. I only show how it works in the program code - multiplication of time tick for ship physics as some huge factor. This principle conserves orbital mechanics of the flight and makes FTL flights more interesting compared to usual "arcade" FTL flights in other games.

    Quote (curiousepic)
    Micro black holes can (theoretially) be any mass.

    Yes, and quickly evaporize by Hawking radiation.

    Quote (curiousepic)
    There are a few concepts for using a mini-black hole for normal sub-light propulsion of a ship though, is that what you're referring to?

    Yes. Black holes can accelerate gas flow to 0.3-0.5 c - this is clearly seen in active galaxy cores. This may be useful to obtain reactive thrust, if we can create micro black hole and hold it inside the ship's engine with a electromagnetic fields.

    *





     
    curiousepicDate: Monday, 19.12.2011, 19:48 | Message # 8
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    Quote (SpaceEngineer)
    I don't work on physical explanation of how hyperaccelerator works. I only show how it works in the program code


    Hehe, ok, well feel free to use my theory as background info.

    But one question about conservation of orbital mechanics. You give the example of travel from Earth to Mars:
    Quote (SpaceEngineer)
    The ship or player calculates the transition orbit; the moment of engaging and disengaging of the main rocket engines. Once the ship reaches the engagement point, it accelerates to its preset travel speed using main engines. Then the ship flies by inertia and reaches Mars within several months.

    Does the ship set up the transition orbit the same as if they were going to use sub-light engines? Or does it factor in the FTL velocity into the transition orbit? The preliminary orbital maneuvers for these two cases are different. If it's a normal Hohmann trajectory (or even Brachistichrone), and the ship uses FTL after the first burn, they will end up way ahead of Mars. So you must account for the fact that Mars only moves for a few seconds of the duration of the FTL flight, instead of the half-year or so it would take for the Hohmann or Brachistichrone trajectory. Is this right?





    My ideal preferences for visual design of the mothership and technology in SE
    Harry Potter and the Methods of Rationality
     
    SpaceEngineerDate: Tuesday, 20.12.2011, 00:33 | Message # 9
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    Quote (curiousepic)
    Does the ship set up the transition orbit the same as if they were going to use sub-light engines? Or does it factor in the FTL velocity into the transition orbit? The preliminary orbital maneuvers for these two cases are different. If it's a normal Hohmann trajectory (or even Brachistichrone), and the ship uses FTL after the first burn, they will end up way ahead of Mars. So you must account for the fact that Mars only moves for a few seconds of the duration of the FTL flight, instead of the half-year or so it would take for the Hohmann or Brachistichrone trajectory. Is this right?


    Right. In game interface I plan to make rendering of precomputing orbit - show it in 3D in normal mode and map mode. For taking into account FTL flying, engine will calculate a bunch of orbits: for non-FTL flight, for warp 1 (10x), warp 2 (100x), warp 3 (1000x), etc.

    BTW, how to name acceleration factor? "Warp" is not perfect for this, as long as it is not a warp engine.

    *





     
    curiousepicDate: Tuesday, 20.12.2011, 01:19 | Message # 10
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    Quote (SpaceEngineer)
    In game interface I plan to make rendering of precomputing orbit - show it in 3D in normal mode and map mode.

    That sounds awesome!

    Quote (SpaceEngineer)
    ill calculate a bunch of orbits: for non-FTL flight, for warp 1 (10x), warp 2 (100x), warp 3 (1000x), etc.

    BTW, how to name acceleration factor? "Warp" is not perfect for this, as long as it is not a warp engine.

    Oh, I didn't realize there would be multiple factors. I assumed that the factor would depend on the gravity gradient along the flight path, since you said gravity affects the hyperaccelerator's performance. Are you not going to make the warp depend on local gravity?

    EDIT: Oh, I see I misinterpreted that part. I understand now. So what will determine the warp factor? Just the type of "core" you have, something that can be upgraded?





    My ideal preferences for visual design of the mothership and technology in SE
    Harry Potter and the Methods of Rationality


    Edited by curiousepic - Tuesday, 20.12.2011, 01:58
     
    SpaceEngineerDate: Tuesday, 20.12.2011, 11:49 | Message # 11
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    I can't answer you now. Maybe automatic precomputation or manual adjusting of "hyperorbit" will be complicated if warp factor depends on local gravity. In this case, that factor will be dependant only on a ship's core parameters and can be changed from 1 to maximum possible value by the pilot.

    And, I repeat my question: does anyone have a suggestion for what name to give the acceleration factor? "Warp" is not good for this. Maybe "hyper"? "My ship is flying at hyper 6.35"...

    *





     
    curiousepicDate: Tuesday, 20.12.2011, 15:52 | Message # 12
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    I think simply "Factor" would be ok. Otherwise it should be the same or relate to the name of the FTL drive or core. Perhaps:

    Core Factor
    Superluminal Factor
    Anti-Dilation Factor
    Veloceration Factor (combination of velocity and acceleration, but this sounds kind of silly, very 1950s-ish)
    Absolute Factor (references the need to match absolute velocity relative to the universe)
    Compression Factor
    Contraction Factor
    Hyperkinetic Factor
    Chronokinetic Factor
    Metakinetic Factor (I like Meta and Para because they imply "outside the normal rules")
    Parakinetic Factor
    Romanyuk Factor smile

    I personally like "Core Factor", "Absolute Factor" (Absolute Acceleration Drive), and "Parakinetic Factor" (Parakinesis Drive).





    My ideal preferences for visual design of the mothership and technology in SE
    Harry Potter and the Methods of Rationality


    Edited by curiousepic - Tuesday, 20.12.2011, 15:54
     
    EnDSchultzDate: Sunday, 08.01.2012, 05:31 | Message # 13
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    A P.K Drive, huh? Does have a certain ring to it. (First post, whoo!)
     
    TalismanDate: Sunday, 08.01.2012, 06:18 | Message # 14
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    Quote (curiousepic)
    (I like Meta and Para because they imply "outside the normal rules")


    What about just "meta"

    "I'm traveling at 4.5 meta"

    That sounds pretty cool. cool





     
    HardtsDate: Sunday, 08.01.2012, 14:14 | Message # 15
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    You could simply use "C" (lightspeed), and a multiplier - For instance: C-0.2, C-0.5, C-2.5 and so on.

    That could simplify things. And if you need to use it in some context, you could call it the c-factor





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    Edited by Hardts - Sunday, 08.01.2012, 14:16
     
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