Agreed on that minimum G rating, but it totally screws up the economics of the Type A.
Maybe that's why the Type R Subbie has Size C drives -- to get 1.5G? Doesn't explain the Jump Drive being Size C though.
CT Only: Big Far Trader (Type R2)
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Maybe that's why the Type R Subbie has Size C drives -- to get 1.5G? Doesn't explain the Jump Drive being Size C though.
It takes an air/raft a number of hours equal to the world's size to reach or land from orbit; therefore it would take any vessel on antigrav a similar time, is the thinking.
Freefalling at terminal velocity and trying to catch yourself at the last moment is not going to be a recommended procedure.
:nonono:
It takes an air/raft a number of hours equal to the world's size to reach or land from orbit; therefore it would take any vessel on antigrav a similar time, is the thinking.
Freefalling at terminal velocity and trying to catch yourself at the last moment is not going to be a recommended procedure.
Aerobraking could help a little.
Lithobraking, not so much.
mike wightman
SOC-14 10K
This is how Space X lands its reusable components. It worked for starship for 95% of its mission profile - once they get the bugs worked out this is exactly how is will return from orbit.Freefalling at terminal velocity and trying to catch yourself at the last moment is not going to be a recommended procedure.
Straybow
SOC-14 1K
IMTU ships normally rate at around ½G. This is because Trav (and every other game I've been able to peek into) assumes linear power requirement for acceleration. In truth, power is proportional to square of acceleration.
This hard-SF approach makes 6G completely impractical. What would get 4G in Trav tables becomes 2G, and if using expanded ratings, 9G becomes 3G. Re-assessing the power required cuts deeply as well. In exchange, ships get performance that depends on total mass, so that lightly loaded ships can
When very deep inside a gravity well, within 5% of planetary radius, grav drive acts synergistically to "float" up to double the mass compared to power required to produce the rated acceleration. In addition, overdrive can further boost the rated acceleration by +50% for about ten minutes, at a cost of +100% input power. The combination allows ½G drives to land on and take off from 1G worlds.
Drives rated at ½G or less can be built to double overdrive standards. This allows operation at +100% output from +200% input power for a minute or so. This is sufficient to allow take-off on 1½G worlds, reaching an altitude at which the ship can lose altitude under "float" while building lateral velocity.
This hard-SF approach makes 6G completely impractical. What would get 4G in Trav tables becomes 2G, and if using expanded ratings, 9G becomes 3G. Re-assessing the power required cuts deeply as well. In exchange, ships get performance that depends on total mass, so that lightly loaded ships can
When very deep inside a gravity well, within 5% of planetary radius, grav drive acts synergistically to "float" up to double the mass compared to power required to produce the rated acceleration. In addition, overdrive can further boost the rated acceleration by +50% for about ten minutes, at a cost of +100% input power. The combination allows ½G drives to land on and take off from 1G worlds.
Drives rated at ½G or less can be built to double overdrive standards. This allows operation at +100% output from +200% input power for a minute or so. This is sufficient to allow take-off on 1½G worlds, reaching an altitude at which the ship can lose altitude under "float" while building lateral velocity.
mike wightman
SOC-14 10K
Why not just increase the made up power generation ability of the power plants to make up for it so you can keep the listed performance?
If mass was the factor that decided performance rather than volume then we can easily work backwards from how much work is required to move a mass a the selected acceleration - such a calculation usually requires Traveller power plants to output at a much higher order of magnitude.
Also if you want to get really pedantic with stuff like this you have to go back to CT LBB2 and use the optional rule for displacement during the turn in which you accelerate - something that is missing from later versions...
If mass was the factor that decided performance rather than volume then we can easily work backwards from how much work is required to move a mass a the selected acceleration - such a calculation usually requires Traveller power plants to output at a much higher order of magnitude.
Also if you want to get really pedantic with stuff like this you have to go back to CT LBB2 and use the optional rule for displacement during the turn in which you accelerate - something that is missing from later versions...
The reason they do that (or can do that) is because their rockets yield more than 1G thrust (even with most of the engines shut down and the remaining one(s) throttled down as far as possible) in their near-empty boosters.
Timing is critical. Achieve zero downward velocity too soon and the dang thing starts going back up again...
Plus, they're using non-fictional propulsion that can't provide full thrust for four weeks straight.
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WAIT WAIT WAIT...
The simplified rule implies the ships/craft are accelerating at 2G (or 2x rated Gs) for the first half of the turn and coasting for the second half (or something a lot like that).
And that solves it. The "overload" capability is already there, but can't be used for more than half a combat turn before having to shut the drive down entirely for half a turn.
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My 2G half the time assertion works for accel out to jump then decel in, course the faster your delta vee the more correction involved if your jump is not on target. If you use the 'kill vee on exit from jump' rule then the burn-flip-burn times apply.
That still provides value though for less time 'at risk'.
A way to go might be to go at a little less then max delta vee to allow for correction, but it would still be coming in faster and meantime if you don't have to correct you just drift at the higher velocity until it is time to decel. Still makes pirate matching less fun.
I think the pirates go two ways to deal with fast/patrolled targets- they stand off with a corsair mothership that threatens ruining the victim ship and gets them to dump off x tons of cargo and don't try to match course, and high-G small craft do the boarding and/or valuable dumped cargo pickup.
Really smart pirates will have intel on the target lading already and insist on specific cargo being dumped, with penalties on a later encounter if their demanded cargo was substituted with a ringer.
I had a thread on this whole 1G thing a few years ago where we went over much of what people are presenting here and a few other option, I can find it and link if any are interested.
But in the meantime this could be played for another type of flavor, you could decide the 1G ships just CAN'T take off from 1G+ planets and have to go to Starport Up stations. The CT valuation for cargo is that it has to be delivered Up or Down depending on where it was picked up so most of the time the 1G ships would be stuck doing station to station delivery.
This ruling would help the carried higher G small craft make more sense as a delivery bus for passengers and cargo. You could even 'reward' such ships that have small craft or 2G maneuver with an extra 1D of cargo lots/passengers if they are slated to provide Starport Down-to-Down service.
If you use my proposed +1D Down variant, then 1G captains might look for going from small planet to small planet opportunities to get full ship profits.
That still provides value though for less time 'at risk'.
A way to go might be to go at a little less then max delta vee to allow for correction, but it would still be coming in faster and meantime if you don't have to correct you just drift at the higher velocity until it is time to decel. Still makes pirate matching less fun.
I think the pirates go two ways to deal with fast/patrolled targets- they stand off with a corsair mothership that threatens ruining the victim ship and gets them to dump off x tons of cargo and don't try to match course, and high-G small craft do the boarding and/or valuable dumped cargo pickup.
Really smart pirates will have intel on the target lading already and insist on specific cargo being dumped, with penalties on a later encounter if their demanded cargo was substituted with a ringer.
I had a thread on this whole 1G thing a few years ago where we went over much of what people are presenting here and a few other option, I can find it and link if any are interested.
But in the meantime this could be played for another type of flavor, you could decide the 1G ships just CAN'T take off from 1G+ planets and have to go to Starport Up stations. The CT valuation for cargo is that it has to be delivered Up or Down depending on where it was picked up so most of the time the 1G ships would be stuck doing station to station delivery.
This ruling would help the carried higher G small craft make more sense as a delivery bus for passengers and cargo. You could even 'reward' such ships that have small craft or 2G maneuver with an extra 1D of cargo lots/passengers if they are slated to provide Starport Down-to-Down service.
If you use my proposed +1D Down variant, then 1G captains might look for going from small planet to small planet opportunities to get full ship profits.
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Apples and oranges.
Why does it take an air/raft so long to reach orbit? Low power-to-weight ratio, of course. Why can SpaceX flight platforms decelerate quickly and make thrust-borne landings? High power-to-weight ratio, of course.
Antigrav is not a high power-to-weight source of thrust; look at the ploddingly-slow vehicles that use it. And bear in mind that gravitically-propelled spacecraft in Traveller do not (or at least should not) use aerobraking; they fly down from orbit, possibly even at subsonic speeds (depending on local noise-abatement requirements). If you land at the starport with scorch marks all over the ventral side of your spacecraft, you need to fire your pilot and find a competent replacement.
Rocketry is simply not a good analogy to reactionless drives, KSP or no KSP.
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Grav vehicles probably should use aerobraking when practical, and be designed for it when it fits their use profile.
That said, most aren't used that way and won't be equipped to do it.
IMTU there's an ablative-foam reentry kit available for Air/Rafts. Stows to about 2m^3, probably about 400kg (hadn't given much thought to how much it weighs). It's like the 1960's-era MOOSE individual re-entry system, but far larger. Basically, wrap a "squared-off teardrop"-shaped bag around the craft, hook cables to the four corners (they join above the center of the craft at the pointy end of the teardrop and connect to a drogue chute), and fill the bag with expanding ablative foam.
Any foam that didn't burn away on reentry can be removed by spraying it with solvent (included with the kit).
At advanced TLs, it's done with integral heat shielding, and grav fields to keep the ionized plasma away from the vehicle's occupants. Or just using reactionless thrusters to decelerate so aerobraking isn't necessary.
That said, most aren't used that way and won't be equipped to do it.
IMTU there's an ablative-foam reentry kit available for Air/Rafts. Stows to about 2m^3, probably about 400kg (hadn't given much thought to how much it weighs). It's like the 1960's-era MOOSE individual re-entry system, but far larger. Basically, wrap a "squared-off teardrop"-shaped bag around the craft, hook cables to the four corners (they join above the center of the craft at the pointy end of the teardrop and connect to a drogue chute), and fill the bag with expanding ablative foam.
Any foam that didn't burn away on reentry can be removed by spraying it with solvent (included with the kit).
At advanced TLs, it's done with integral heat shielding, and grav fields to keep the ionized plasma away from the vehicle's occupants. Or just using reactionless thrusters to decelerate so aerobraking isn't necessary.
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Straybow
SOC-14 1K
Well, I should know not to write a post after I've fallen asleep in my chair...
Based on a calculation for an equivalent rocket burn, the nominal 2 EP scout would need more than 12 EP for a 2 G burn (based on 1 ton mass per dT). Even a 1 G burn would take 3 EP. The physics doesn't work well, and merely ramping up the output of the magical nearly-free-energy-without-waste-heat power plant doesn't help.
The Air/Raft already breaks ground. Somehow it can counter gravity at a minimal energy cost compared to ~¼ EP (for 4 dT vehicle proportional to 3 EP 100 dT Scout). I believe Striker assumes vehicle power plants are roughly 1 MW/ton mass, so the A/R is probably more like 2 MW, or 0.008 EP. "Floating" in a gravity well can be done for 1/32 of the power of producing an equivalent grav drive.
We need to bridge the gap. Yes, Striker and EP ratings aren't vanilla CT, but that's where we get canonical power ratings expressed in real world terms.
Proneutron
SOC-13
Freefalling at terminal velocity and trying to catch yourself at the last moment is not going to be a recommended procedure.
Not LAST moment. Stop 5,000' up would be fine. However you can take an air-raft down at s00+ mph as it doesn't require high thrust to weight going down. ONLY up is where that ratio is problematic. E.g. a Piper Cherokee can only climb at ~50 mph max. But can descend at >150 mph. And that only because it has wings slowing it down. An air-raft could easily hit 200 mph. Or about 40 minutes from LEO altitude to landing.
Proneutron
SOC-13
Same with ships. No need to come screaming in. One just hovers out in space above where you want to land and you lower yourself down through the atmosphere. You have basically infinite Delta-V and grav lift higher than the planetary grav level.
Condottiere
SOC-14 5K
You could assume that it works about the same as an air/raft descending.
A rather large and clunky air/raft.
A rather large and clunky air/raft.
Assuming grav lift. If all you have is push from the maneuver drive, you might not.
"Hot" reentry is for 1G ships (or 1.1G grav vehicles) that are braking from orbital velocity, since (depending on the world size) they may not have a lot of acceleration left over after overcoming gravity to use for slowing down.
EDIT: 1G ships can kill orbital velocity pretty darn quickly, since unlike grav vehicles they've got the full 1G to play with (grav vehicles get [local gravity straight up]+0.1G lateral or vertical). Size 8, they can drift down, but won't be able to get back up again. Size 9 or 10, they're falling at 1-2m per second^2 which is the problem we're discussing here.
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TNE suggests contra grav. These do not provide lift, but negate 99% of gravity, giving thrusters the job of actually moving the ship. It mentions that in Dense atmosphere, ships are almost buoyant.
The question is does this negate up to a certain G rating? Or is it absolute. Stars and gas giants have quite the pull, so will contra grav allow a ship to defeat these? or only some of it?
The question is does this negate up to a certain G rating? Or is it absolute. Stars and gas giants have quite the pull, so will contra grav allow a ship to defeat these? or only some of it?
I figure that all antigrav applications of gravitics are probably limited to 2Gs (20 meters per second per second), like artificial gravity fields are -- mostly to keep it from becoming easily weaponized by miscreant PCs, honestly.
Proneutron
SOC-13
Not relevant. Grav, lifters, thrust plates. It ALL equals x amount of thrust. AND, unlimited deta-v. As long as you have more "thrust" than gravity pulling on you you can slow to a hover out in space over the part of the planet you want to land on and slowly go straight down. The "may not have a lot of acceleration left over after overcoming gravity to use for slowing down." only applies with limited fuel reaction drives. NOT to Trav , Grav or Thrust plate dives.
Relevant.
Grav lifters (as I interpret them from the Air/Raft description) have thrust that's different in different directions. Against the local gravity field, it's local gravity plus 0.1G. Downward, it can be as high as local gravity plus 0.1G (because it can fall at local gravity and push (pull?) downwards at 0.1G beyond that). Perpendicular to the local gravity field, it's just 0.1G. This means it takes a while to kill an orbital velocity of 7.8km/sec with just 1m/sec^2.
It's not a fuel or total energy available limit, it's the limited (de)acceleration available along the orbital track.
Aerobraking can provide up to a few Gs of deceleration, significantly reducing descent times. If you're in a Dragon or Soyuz capsule, you don't have any choice in the matter -- aerobraking is the only way to go. If you're in a flying antigravity convertible, you really don't want to hit the upper atmosphere at Mach 20 or whatever (the ablative re-entry kit I mentioned above solves this).
So you decelerate against your orbital path until reaching a safe re-entry speed, rather than accelerating downward. Also note that if you're in orbit, you can't use local gravity to add to downward acceleration available. You won't fall if you turn the antigravity drive off because it's already at zero. (Below orbital velocity, you start accelerating downward -- falling -- unless you dial up the antigravity to compensate, though.)
Maneuver drives (from CT canon) have the ability to apply their thrust in any direction regardless of the local gravity field*. This means they can kill orbital velocity in minutes.
*Later revisions nerf maneuver drives outside 1000D or something like that, but it doesn't matter for this discussion.
Grav lifters (as I interpret them from the Air/Raft description) have thrust that's different in different directions. Against the local gravity field, it's local gravity plus 0.1G. Downward, it can be as high as local gravity plus 0.1G (because it can fall at local gravity and push (pull?) downwards at 0.1G beyond that). Perpendicular to the local gravity field, it's just 0.1G. This means it takes a while to kill an orbital velocity of 7.8km/sec with just 1m/sec^2.
It's not a fuel or total energy available limit, it's the limited (de)acceleration available along the orbital track.
Aerobraking can provide up to a few Gs of deceleration, significantly reducing descent times. If you're in a Dragon or Soyuz capsule, you don't have any choice in the matter -- aerobraking is the only way to go. If you're in a flying antigravity convertible, you really don't want to hit the upper atmosphere at Mach 20 or whatever (the ablative re-entry kit I mentioned above solves this).
So you decelerate against your orbital path until reaching a safe re-entry speed, rather than accelerating downward. Also note that if you're in orbit, you can't use local gravity to add to downward acceleration available. You won't fall if you turn the antigravity drive off because it's already at zero. (Below orbital velocity, you start accelerating downward -- falling -- unless you dial up the antigravity to compensate, though.)
Maneuver drives (from CT canon) have the ability to apply their thrust in any direction regardless of the local gravity field*. This means they can kill orbital velocity in minutes.
*Later revisions nerf maneuver drives outside 1000D or something like that, but it doesn't matter for this discussion.
