Ship Design Philosophy
- Thread starter Condottiere
- Start date
Condottiere
Emperor Mongoose
Since I'm currently concentrating on the military aspects of the Confederation, I was aware of the existence of that subchapter, but it didn't have relevance at this time.
Overthrust Methods
It would seem that a 1g ship landed on a 1.4g world is stuck there if it cannot generate enough aerodynamic lift to augment its drives but this is not the case. A ship with inadequate drive power cannot hover or climb vertically but it can produce enough thrust to brake a take-off or make a launch. Doing so requires overcharging the ship’s thrust system in order to generate a few moments of increased power. Where the difference is minimal, such as a 1g ship on a 1.03g world, the automated systems that run the drive will do this automatically and the effects are unlikely to be felt by passengers. Anything over a 0.05g difference requires the manual intervention of a skilled pilot.
This overthrust is only generated for a few moments. Once the drive ‘relaxes’ back to its normal thrust level the process cannot be repeated for 2Dx5 minutes. On take-off this means the ship bangs back down onto the pad; in the case of a landing the ship fails to slow enough and comes in hard. The effects of this ‘unscheduled terrain interaction’ are determined by the Severity table.
Take-off with inadequate thrust is an unpleasant business. The vessel must generate enough overthrust to make a near-horizontal take-off and get far enough from the ground that a (very shallow) climb can be maintained. Whereas a high-thrust ship can go more or less straight up, one with insufficient thrust can only accelerate in a direction just above the horizontal, slowing gaining enough speed to reach orbital distance. Essentially this ship is using thrust to flatten its fall enough that the curvature of the planet increases its altitude above the surface. Terrain may make this sort of take-off impossible or channel low-thrust craft into a narrow clear lane. A take-off of this sort requires a Difficult (10+) Pilot check, with an additional DM-1 for every 0.1g the planet’s gravity exceeds the vessel’s normal Thrust.
There's more, but even then, it's prickly hot potato to interpret.
Effects felt by passengers and crew upto a tad under half an additional gee would be about the same as a passenger plane taking off, assuming overclocking doesn't extend to inertial compensation.
As far as I can tell, you need sustained overthrust to reach orbit, and in an atmosphere, streamlined hull; not sure what assists lift off on an airless world.
Overthrust Methods
It would seem that a 1g ship landed on a 1.4g world is stuck there if it cannot generate enough aerodynamic lift to augment its drives but this is not the case. A ship with inadequate drive power cannot hover or climb vertically but it can produce enough thrust to brake a take-off or make a launch. Doing so requires overcharging the ship’s thrust system in order to generate a few moments of increased power. Where the difference is minimal, such as a 1g ship on a 1.03g world, the automated systems that run the drive will do this automatically and the effects are unlikely to be felt by passengers. Anything over a 0.05g difference requires the manual intervention of a skilled pilot.
This overthrust is only generated for a few moments. Once the drive ‘relaxes’ back to its normal thrust level the process cannot be repeated for 2Dx5 minutes. On take-off this means the ship bangs back down onto the pad; in the case of a landing the ship fails to slow enough and comes in hard. The effects of this ‘unscheduled terrain interaction’ are determined by the Severity table.
Take-off with inadequate thrust is an unpleasant business. The vessel must generate enough overthrust to make a near-horizontal take-off and get far enough from the ground that a (very shallow) climb can be maintained. Whereas a high-thrust ship can go more or less straight up, one with insufficient thrust can only accelerate in a direction just above the horizontal, slowing gaining enough speed to reach orbital distance. Essentially this ship is using thrust to flatten its fall enough that the curvature of the planet increases its altitude above the surface. Terrain may make this sort of take-off impossible or channel low-thrust craft into a narrow clear lane. A take-off of this sort requires a Difficult (10+) Pilot check, with an additional DM-1 for every 0.1g the planet’s gravity exceeds the vessel’s normal Thrust.
There's more, but even then, it's prickly hot potato to interpret.
Effects felt by passengers and crew upto a tad under half an additional gee would be about the same as a passenger plane taking off, assuming overclocking doesn't extend to inertial compensation.
As far as I can tell, you need sustained overthrust to reach orbit, and in an atmosphere, streamlined hull; not sure what assists lift off on an airless world.
As I read it you can overthrust the ship to get it off the ground but after that would need to rely on aero lift to get high enough to break free and using orbital velocities to aid in achieving escape velocity.
I think under all but emergency situations a captain would not take their ship on a planet for which they do not have sufficient normal thrust to achieve orbit. The reality is that a thrust of 2 would be sufficient in the vast majority of situations and Free Traders and such would simply avoid planets without shuttle services or a spaceport in orbit.
Finally most commercial ships have an air/raft which would not have thrust problems and could get to and from orbit with passengers, though not significant cargo.
I think under all but emergency situations a captain would not take their ship on a planet for which they do not have sufficient normal thrust to achieve orbit. The reality is that a thrust of 2 would be sufficient in the vast majority of situations and Free Traders and such would simply avoid planets without shuttle services or a spaceport in orbit.
Finally most commercial ships have an air/raft which would not have thrust problems and could get to and from orbit with passengers, though not significant cargo.
Unless you have some form of lifting surface (wing as an example) you would need enough thrust to exceed 1G in order to get off the ground. If you assume that a m-drive can exert 1G of forces in multiple directions at once (vertically and horizontally) then you could indeed "fly" once off the ground but if 1G total at best you could hover since even tilt thrust redirects some of the thrust for forward motion, removing some of the lift thrust.
For purposes of gameplay I would not consider this important and would argue that a 1G thrust capable ship is able to land safely and achieve orbit on a 1G planet but would not be able to do so safely on a planet significantly above 1.0G, arbitrarily I would say above 1.1G.
If you want to treat achieving orbit using pseudo physics and say that a MDrive-1 propels a ship at 1G of acceleration in the absence of a gravitational field then I would argue that from a practical standpoint such a ship could not achieve orbit. You may be able to achieve orbit using lifting surfaces for lift and a continual thrust forward to achieve escape velocity. In reality drag coeffecient vs atmospheric density makes this questionable given the mass of a starship as compared to its surface area. From a practical stance if M-Drive cannot somehow counteract the gravitational pull then it would need a MDrive-2 to achieve orbit in a reasonable time frame.
But this is space opera, not scientific simulation so a bit of hand waving is not that big a deal.
For purposes of gameplay I would not consider this important and would argue that a 1G thrust capable ship is able to land safely and achieve orbit on a 1G planet but would not be able to do so safely on a planet significantly above 1.0G, arbitrarily I would say above 1.1G.
If you want to treat achieving orbit using pseudo physics and say that a MDrive-1 propels a ship at 1G of acceleration in the absence of a gravitational field then I would argue that from a practical standpoint such a ship could not achieve orbit. You may be able to achieve orbit using lifting surfaces for lift and a continual thrust forward to achieve escape velocity. In reality drag coeffecient vs atmospheric density makes this questionable given the mass of a starship as compared to its surface area. From a practical stance if M-Drive cannot somehow counteract the gravitational pull then it would need a MDrive-2 to achieve orbit in a reasonable time frame.
But this is space opera, not scientific simulation so a bit of hand waving is not that big a deal.
Condottiere
Emperor Mongoose
This is likely to get circular.
So, I'm going to get on the carousel.
Flying wing.
So, I'm going to get on the carousel.
Flying wing.
By all means stick to your rules. I do not intend to suggest otherwise. To answer your question reducing lift happens first. Even specialized ultralight planes with massive wings have not come even close to orbit. Traveller ships have no such lift surface to weight ratios.
Purely speculation but I would guess a planet at the high end of TL8 or low end of TL9 could do it with a specialized craft without gravatics. With gravatics modern aerodynamics may no longer apply directly so I can't speculate.
Hypothetically since the m-drive is not dependent on chemical reaction or pressure differentials the ship can go faster and faster until it achieves orbit but that is purely speculation. To reiterate I would generally hand wave this away unless the planet was notably higher gravity than the drive value but enjoy thinking about such things.
Edit:
To date the highest acknowledged flight by a plane is the X15 at 314,688 feet (roughly 60 miles). Low earth orbit is roughly 1,200 miles.
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does not work that way in reality
Clarification, LEO is below 1200 miles, not floor 1200 miles. Most satellites sit in the upper third with geostationary being above LEO.
Theoretically anything above the ionosphere can achieve stable orbit IIRC but my college days are long past.
EDIT: Also for clarity, LEO is not critical if all you want to do is achieve orbit, but becomes important as an indicator of ability to escape orbit. This was a discussion on escaping a planet using lift to achieve altitude. In order to do this with thrust not exceeding the pull of gravity you must first get high enough to have a lowered pull. The ISS is still well within the gravity well, they are not even close to outside of the well, they are just continually falling.
EDIT2: Hypothetically you achieve stability at some altitude and continue powering forward in such a way that you can accelerate past any drag you may be experiencing and eventually you would achieve escape velocity. Now I kind of want to figure out at what height drag is negligible and how long it would take to achieve escape velocity at that altitude using forward thrust at 9.8 m/s^2 but TBH the math is not worth it. Traveller spacecraft for all practical purposes have infinite fuel for thrust (4 weeks minimum?) so eventually they would make it I think. Interesting from an academic stance though.
Thank you everyone for approaching it so constructively.
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Condottiere
Emperor Mongoose
Manoeuvre drive - you want to position the spaceship where the local gravity drops below default thrust, which would be how many kilometres above the surface?
Also, the manoeuvre drive thrust is constant, so not dependent on local environmental conditions.
As regards the hull, configuration may interfere with the efficient transition through the atmosphere.
Speaking of which, subconfiguration flying wing is going to generate more lift than subconfiguration wedge.
Also, the manoeuvre drive thrust is constant, so not dependent on local environmental conditions.
As regards the hull, configuration may interfere with the efficient transition through the atmosphere.
Speaking of which, subconfiguration flying wing is going to generate more lift than subconfiguration wedge.
Using earth as an baseline. ISS at 261 miles is at .88Gs. So a planet of the same size as earth but a 10% higher gravity would have .968Gs at the same height. Different planets with different radii, gravitational pull, and atmospheric density would not follow this. Each planet would have different challenges.
The infinite thrust is what allows the escape at all given thrust equal to the gravity of the planet itself. It also sort of obviates the need to worry about drag etc... If we allow:
* (for practical purposes) unlimited speed within atmo
* we can achieve enough forward velocity to achieve stable flight using lift
* for sake of simplicity assume 1G of thrust is enough to overcome drag regardless of velocity
then eventually the object would achieve orbit.
Just don't land on a 1G planet without atmosphere.
I may take this to another thread if people actually want to discuss this but if we assume a spacecraft can achieve 1G of acceleration regardless of atmosphere that implies that gravatics are ignoring drag. If gravatics ignore drag then by definition they are also ignoring lift (lift and drag being the same effect, just in different directions).
This makes my head hurt.
EDIT: ofc if they did not experience drag then streamlined vs non-streamlined would not make a difference so thankfully we can call it a simplification rather than a law of physics in the Traveller universe.
This makes my head hurt.
EDIT: ofc if they did not experience drag then streamlined vs non-streamlined would not make a difference so thankfully we can call it a simplification rather than a law of physics in the Traveller universe.
Condottiere
Emperor Mongoose
Supposedly [acceleration factor minus local gravity] equals factor one plus, it's hypersonic.
Drag is still a factor, otherwise the rules wouldn't bother with streamlining.
Obviously, you could use some form of rocket assist, since the rules specifically allow that add on.
Drag is still a factor, otherwise the rules wouldn't bother with streamlining.
Obviously, you could use some form of rocket assist, since the rules specifically allow that add on.
Condottiere
Emperor Mongoose
I kinda suspect that air resistance has something to do with that.
Then we have a planet without an atmosphere, so I suppose acceleration goes back to default, minus local gravity.
Then we have a planet without an atmosphere, so I suppose acceleration goes back to default, minus local gravity.
Condottiere
Emperor Mongoose
I get the feeling this hasn't really been thought out to it's conclusion, logical or otherwise.
Technological level seven reactionary rockets factor up to three, which is about as far as I would go for sustained acceleration.
Technological level ten you can max out customization, which in this case, is limited to fuel efficiency, but at the same time, you have the introduction of manoeuvre drive factor three.
Technological level seven reactionary rockets factor up to three, which is about as far as I would go for sustained acceleration.
Technological level ten you can max out customization, which in this case, is limited to fuel efficiency, but at the same time, you have the introduction of manoeuvre drive factor three.
