FFW doing it my way

[collins355]

That table was retconned, the header is wrong as it is not top speed in a vacuum - the maximum speed in a vacuum is 0.99c...

Yes, I did see the point made in arguing for retcon-ing, but you can't work out craft speeds in the atmosphere in MegaTrav craft design without the table.

 

[Sigtrygg]

I think there was a correction in a digest magazine, it was certainly changed for COACC.

The MT errata document has this:

"Page 86, Top Vacuum Speed (correction and addition): For flying vehicles, especially those that can go outside the atmosphere, top vacuum speed has no real meaning. Other than the speed of light, there really is no such thing as “top speed” in a vacuum. The craft can accelerate as long as it wants, and can attain any speed desired—limited only by its duration and acceleration. Therefore, acceleration in Gs is a more sensible and useful number than top vacuum speed, since it tells you how quickly the craft can change its speed. Once you know the craft’s maximum acceleration rate, you can compute the travel time using the basic travel time formula found in the Referee’s Companion. Therefore, Top Vacuum Speed should be replaced by MaxAccel in craft profiles.
Top Speed applies to craft operating in a standard atmosphere only. Note that wheeled, tracked, and legged vehicles are subject to the same top speed restrictions as flying craft, based on their streamlining. For example, an unstreamlined wheeled vehicle can never exceed 300 kph in a standard atmosphere. If the wheeled vehicle needs to go faster, it must be streamlined, just as any flying vehicle."

 

[Condottiere]

As I recall, current practice is that for spacecraft within a local gravity well, minus local gravity, and if remaining acceleration is factor one plus, hypersonic.

Gravity motored vehicles would probably depend on altitude, acceleration minus felt gravity.

 

[collins355]

I think there was a correction in a digest magazine, it was certainly changed for COACC.

The MT errata document has this:

"Page 86, Top Vacuum Speed (correction and addition): For flying vehicles, especially those that can go outside the atmosphere, top vacuum speed has no real meaning. Other than the speed of light, there really is no such thing as “top speed” in a vacuum. The craft can accelerate as long as it wants, and can attain any speed desired—limited only by its duration and acceleration. Therefore, acceleration in Gs is a more sensible and useful number than top vacuum speed, since it tells you how quickly the craft can change its speed. Once you know the craft’s maximum acceleration rate, you can compute the travel time using the basic travel time formula found in the Referee’s Companion. Therefore, Top Vacuum Speed should be replaced by MaxAccel in craft profiles.
Top Speed applies to craft operating in a standard atmosphere only. Note that wheeled, tracked, and legged vehicles are subject to the same top speed restrictions as flying craft, based on their streamlining. For example, an unstreamlined wheeled vehicle can never exceed 300 kph in a standard atmosphere. If the wheeled vehicle needs to go faster, it must be streamlined, just as any flying vehicle."

Yes, but that errata never addressed the issue of how one is meant to calculate the top speed of a flying craft inside the atmosphere if the chart is not kosher. The design sequence in RM is very clear in its intent, the designer determines the craft's Man. Thrust, looks up the top vac speed for that thrust on the chart provided and then multiplies it by 0.9 if streamlined to get max speed in a standard atmosphere (and cruise speed and NOE speed in turn). Note the different multipliers for different atmospheres.

I'm very comfortable if the chart remains valid, but is re-named to something like Top Notional Speed. That would take away the insinuation that triggers people that there is a speed limit less than the speed of light for craft in space.

(BTW, the speeds of ground vehicles were always completely bonkers in MegaTrav and remain so with this errata. The idea that by streamlining my truck I can have it capable of speeds 400kph plus is wild)

 

[Sigtrygg]

The default is to calculate top speed in a standard atmosphere for a particular airframe type, you then modify for atmosphere type/density.

As to flying trucks - formula 1 cars have to be designed for aerodynamic downforce to stop them taking off (bad since they don't have flight control surfaces). Sufficient engine capacity to generate acceleration in a truck to give it very high speeds will also need aerodynamics to keep it grounded, you just need a vastly more powerful engine and power density than IC engines can manage... You could put a gas turbine (M1A2 engine) in a transit van... now there is an idea for a youtube channel...

 

[Condottiere]

Pure thrust to have several times twenty eight thousand klix per hour tends to override atmospheric resistance.

Especially, if you neutralize local gravity first.

 

[collins355]

The default is to calculate top speed in a standard atmosphere for a particular airframe type, you then modify for atmosphere type/density.

Sorry but I don't understand what you mean here. Maybe you could step me through how you think the MegaTrav craft design sequence would work to calculate this - absent using the published table.

 

[Sigtrygg]

The table gives a speed limit based on acceleration in a standard atmosphere

this is limited by the maximum speed allowed by the airfame

the maximum speed is then multiplied by a coefficient based on atmosphere type/density

 

[phavoc]

You quoted the computer rules from 81 revised CT, go and check the 77 edition there is no such restriction...

I had to go back and look. You are correct. The rule is from Book 2, 81.

Under the HG79 construction system you designate the hull size and drop tanks are taken from that tonnage, this changed in HG.80 where you can add the drop tanks to the hull.

There are no rules like that in HG'79. The only passage I found was the one that listed the tanks - "-L-Hyd Tanks: Disposable fuel tanks which are fitted outside the ship, and drop away before jump. The result is more interior space available for cargo and passengers. Cost: Cr 10 000 plus Cr1000 per ton of fuel. Usable only with jump drives if a special high capacity accumulator is installed (tech level 12; Cr500 000)." There are no rules for them that I see.

using HG 70 rules the Gazelle puts its 160t of jump fuel in tanks that can be dropped, which reduces the ship to only 240t hence the increase to jump 6 but not further jumps possible.

There are no rules like that regarding tanks. The only rules regarding L-Hyd is that they can drop away before jump. In that case the Gazelle becomes a 300Dton ship (rules say a 240Dton ship is the same as a 300Dton).

You are quoting it yourself, they are adapted from the rules in HG, the version of HG available at the time was '79. Note nowhere in CT canon is a "heavy laser" defined either.

I would not interpret it that way. The quote says they are "inspired" - but no 5Dton bays exist in the rules, and no heavy lasers exist. HG'77 talks about jump torpedoes, but they don't exist anywhere other than Leviathan, and they were de-canonized soon after that publication. Which to me means that the ship violates the rules. One cannot build the Gazelle with the rules unless one takes "inspiration" from them.

HG 80 would not be in production until after JTAS 4 was written, using HG79 rules. The computer rules referencing LBB:2 refer to the && edition since the 81 revision is still a year away at least. The USP is the '79 format.

It's odd that they provide a USP, but utilize the standard ship's papers to describe the ship. It's a mish-mash of books and rules.

The oroginal design sequence in HG'79 has you designating fuel as being in drop tanks, this volume is accounted fo from the hull size selected initially, you do not design a 300t ship and add 100t of drop tanks under HG79, you design a 400t hull and designate 160 tons of jump fueal as being in drop tanks.

It doesn't have you designating. It states Determine fuel tankage and then says "Consider" drop tanks, and "Consider" fuel purification plant. To me that clearly states its an option.

To me, at least, it's not at all clear that your interpretation is the one to go with. I see that design checklist as creating your ship and then consider adding drop tanks. This is the first time they are in place, and the clarity around their existence does not yet exist. It's a giant hole.

If we look at the Book 2 '77 rules, it's pretty clear that the concept was everything is computed based on the original hull displacement. Drop tanks change that concept, but the original rules don't allow for that interpretation. And HG'77 makes it clearly optional, but you still are bound by the other rules (mass, etc).

There are differences from HG 79 that I can not reconcile - how MWM determined the USP rating of the particle accelerators being the main one.

But using HG'79 you can reverse engineer the JTAS 4 Gazelle and get a lot closer than most of the HG designs in S:9. The nuclear damper, the armoured hull all match the 79 USP.

Is there / was there a build-out for the Gazelle ever published? I can't recall seeing one. I have continually found it somewhat annoying that many versions of Traveller have continued the process of designing ships that don't fall within their own design rules.

To be clear, I'm not doing this to be argumentative. I very much like games to follow their own internal rule processes that players are to do as well. So when you see official ships/designs published in the materials and one cannot replicate them (Ships like Annic Nova are exceptions), that's annoying (to me at least). I have always considered the Gazelle to be unbuildable using the rules of any of the versions. And once the updated rules were made the design should have been corrected based on the latest rules. However it was not.

 

[phavoc]

Pure thrust to have several times twenty eight thousand klix per hour tends to override atmospheric resistance.

Especially, if you neutralize local gravity first.

Anti-grav only affects weight and lift, It doesn't do away with drag or the issues related to control due to drag and aero-dynamic forces. The current thrust table showing a 6G ship capable of Mach 30 is just plain silly - not in the troposphere or stratosphere. Once you get above these then higher speeds like that start becoming more realistic.

To be fair, perhaps the MGT table means speed in the thermosphere or exosphere. The ISS travels at Mach 26 in low earth orbit (which is nearly vacuum anyways). IF that's what its referring to, then sure, lets go with it. But there exists no reason for starships to have that speed (let alone it being reasonably attainable) at lower altitudes. It would be far faster for a ship to make a sub-orbital hop than try to travel all the way in the first two layers of atmosphere. The travel times in the early books are for vacuum travel, not atmospheric. COACC had supersonic and hypersonic airframes and engine types (TL6, I think, was 2 TL too low for hypersonic), and top speed for a hypersonic craft was 5,000kph.

With grav tech combined with a space craft, you'd probably see a lot more sub-orbital flights to get around a planet, or dedicated shuttle flights from say NYC to Tokyo if on Earth. Probably you wouldn't see a NYC to LA sub-orbital hop. SR-71 made that run in about 70min. Of course, it was already in the air when it started it's timed run (and it has to refuel since it leaks like a sieve on the ground). A starship would do something similar - take off and get to a higher altitude before being able to go fast.

The thing is a starship is built for space travel, so it's gonna be optimized for that, not atmospheric travel. It only need to get up a few hundred kilometers to LEO to get into its element, so if it pokes around at a few hundred kph from LEO to ground, that's not bad at all. Faster ships could make it faster... but you still have issues related to flight characteristics and control. With anti-grav it'd be a cinch to keep your speed sub-sonic and still be a very reasonable flight envelope.

It'd be a little bit of work, but one could create a chart to make sub-orbital hops for 1 to 6 G ships. Probably more than anyone cares to do though unless it was needed for a specific scenario.

 

[collins355]

Two months into the war and the Outworld Coalition have accumulated 211.5 victory points. Still well short of an automatic victory and Imperial reinforcements from elsewhere in the Sector have started to arrive.
Those reinforcements have already made their presence felt, defeating the combined Sword Worlds fleets at Tavonni on the doorstep of the subsector capital Lanth.
Jewell still holds out, but only just. Emerald and Ruby have fallen.
An Imperial counteroffensive is underway against the Vargr. Pixie has been retaken, and Boughene is under Imperial siege.

 

[MasterGwydion]

Anti-grav only affects weight and lift, It doesn't do away with drag or the issues related to control due to drag and aero-dynamic forces. The current thrust table showing a 6G ship capable of Mach 30 is just plain silly - not in the troposphere or stratosphere. Once you get above these then higher speeds like that start becoming more realistic.

To be fair, perhaps the MGT table means speed in the thermosphere or exosphere. The ISS travels at Mach 26 in low earth orbit (which is nearly vacuum anyways). IF that's what its referring to, then sure, lets go with it. But there exists no reason for starships to have that speed (let alone it being reasonably attainable) at lower altitudes. It would be far faster for a ship to make a sub-orbital hop than try to travel all the way in the first two layers of atmosphere. The travel times in the early books are for vacuum travel, not atmospheric. COACC had supersonic and hypersonic airframes and engine types (TL6, I think, was 2 TL too low for hypersonic), and top speed for a hypersonic craft was 5,000kph.

With grav tech combined with a space craft, you'd probably see a lot more sub-orbital flights to get around a planet, or dedicated shuttle flights from say NYC to Tokyo if on Earth. Probably you wouldn't see a NYC to LA sub-orbital hop. SR-71 made that run in about 70min. Of course, it was already in the air when it started it's timed run (and it has to refuel since it leaks like a sieve on the ground). A starship would do something similar - take off and get to a higher altitude before being able to go fast.

The thing is a starship is built for space travel, so it's gonna be optimized for that, not atmospheric travel. It only need to get up a few hundred kilometers to LEO to get into its element, so if it pokes around at a few hundred kph from LEO to ground, that's not bad at all. Faster ships could make it faster... but you still have issues related to flight characteristics and control. With anti-grav it'd be a cinch to keep your speed sub-sonic and still be a very reasonable flight envelope.

It'd be a little bit of work, but one could create a chart to make sub-orbital hops for 1 to 6 G ships. Probably more than anyone cares to do though unless it was needed for a specific scenario.

I tried to explain this before, but it seemed no one on here could understand sub-orbital flights of 45 minutes from one side of the planet to the other.

Perhaps you have just done a better job of explaining it than I did.

 

[Sigtrygg]

I had to go back and look. You are correct. The rule is from Book 2, 81.

Which therefore doesn't apply.

There are no rules like that in HG'79. The only passage I found was the one that listed the tanks - "-L-Hyd Tanks: Disposable fuel tanks which are fitted outside the ship, and drop away before jump. The result is more interior space available for cargo and passengers. Cost: Cr 10 000 plus Cr1000 per ton of fuel. Usable only with jump drives if a special high capacity accumulator is installed (tech level 12; Cr500 000)." There are no rules for them that I see.

Look at the flow chart for ship construction on page 34:

"4.Determine fuel tankage (blocks 29a, 29b) requirements. p. 29
A. Consider L·Hyd Tanks and Fuel Scoops. p. 32
B. Consider Fuel Purification Plant (block 29c).p. 32"

You determine fuel requirement, then you decide if you are putting it in drop tanks. The drop tanks are not an addition to the hull, they are taken out of available hull volume.

There are no rules like that regarding tanks. The only rules regarding L-Hyd is that they can drop away before jump. In that case the Gazelle becomes a 300Dton ship (rules say a 240Dton ship is the same as a 300Dton).

see above

I would not interpret it that way. The quote says they are "inspired" - but no 5Dton bays exist in the rules, and no heavy lasers exist. HG'77 talks about jump torpedoes, but they don't exist anywhere other than Leviathan, and they were de-canonized soon after that publication. Which to me means that the ship violates the rules. One cannot build the Gazelle with the rules unless one takes "inspiration" from them.

Nor can you build an xboat without a certain interpretation of the rules, or the Annic Nova at all. With the exception of the particle barbettes which appear to be MWM's interpretation of a 10t bay (where did they go...) everything in the Gazelle is legitimate to the USP given in JTAS and built using HG'79

It's odd that they provide a USP, but utilize the standard ship's papers to describe the ship. It's a mish-mash of books and rules.

It is HG79 with MWM inventing the two 5t barbettes in lieu of the 10 ton bay mount

It doesn't have you designating. It states Determine fuel tankage and then says "Consider" drop tanks, and "Consider" fuel purification plant. To me that clearly states its an option.

Having drop tanks is an option, you can just have regular fuel tanks. You don't need a purification plant, it is an option, your point here is lost on me.
Imafine a time before HG'80 when all you have in LBB:3 77 and HG'79 - everything has to be accounted for in hull tonnage. Bolt on drop tanks are part of the HG'80 paradigm that has become dogma.

To me, at least, it's not at all clear that your interpretation is the one to go with. I see that design checklist as creating your ship and then consider adding drop tanks. This is the first time they are in place, and the clarity around their existence does not yet exist. It's a giant hole.

Only when using subsequent rules, as I said in the last bit. Not many people built HG'79, ships, the revisions in HG80 and then 81 LBB: are what most people remember. The Gazelle was built using rules that pre-date those paradim changes - with MWMs usual artistic licence.

If we look at the Book 2 '77 rules, it's pretty clear that the concept was everything is computed based on the original hull displacement. Drop tanks change that concept, but the original rules don't allow for that interpretation. And HG'77 makes it clearly optional, but you still are bound by the other rules (mass, etc).

Exactly, you allocate hull tonnage when building ships, drop tanks are just another item to be accounted for from hull tonnage. At step 4 you have the option of fuel being in normal tanks or drop tanks, either way it is using hull tonnage.

Is there / was there a build-out for the Gazelle ever published? I can't recall seeing one. I have continually found it somewhat annoying that many versions of Traveller have continued the process of designing ships that don't fall within their own design rules.

Crack open HG79, you can get close...

To be clear, I'm not doing this to be argumentative.

Me neither, it is just the consensus of many people having had this discussion for over forty years.

I very much like games to follow their own internal rule processes that players are to do as well.

Travelle rhas never done that sadly, and Mongoose keeps the tradition alive. The original OTU did not use all the rules in 77 edition, and features of the OTU would change as the rules themselves changed. Look at the early Library Data for Capital as an example, or the Battle of the two Suns...

So when you see official ships/designs published in the materials and one cannot replicate them (Ships like Annic Nova are exceptions), that's annoying (to me at least).

Me too, I like to redesign canon ships to see how close I can get.

I have always considered the Gazelle to be unbuildable using the rules of any of the versions. And once the updated rules were made the design should have been corrected based on the latest rules. However it was not.

I completely agree. FF&S fixed it by removing the silly hardpoint restriction and instead using surface area. The same can be done in GT:ISW since hardpoints are linked to surface area.

 

[Condottiere]

Spacecraft are capable of any Speed Band listed in the Vehicles chapter and will typically be going at Hypersonic speeds when entering an atmosphere.

 

[MarcusIII]

Spacecraft are capable of any Speed Band listed in the Vehicles chapter and will typically be going at Hypersonic speeds when entering an atmosphere.

Since the spacecraft have the Δv I wouldn't think they come blazing into the atmosphere when they can just match planetary rotation speed right above their ground target and gently drop into the atmosphere.

 

[Condottiere]

I advise dead slow for non streamlined hull configurations.

 

[MasterGwydion]

Spacecraft are capable of any Speed Band listed in the Vehicles chapter and will typically be going at Hypersonic speeds when entering an atmosphere.

Where is this from? I looked for something like this a few days ago but didn't find it.

 

[Condottiere]

I thought it was Vehicles.

Core, page one hundred seventy four.

 

[MasterGwydion]

I thought it was Vehicles.

Core, page one hundred seventy four.

Found it! Thanks!

 

[phavoc]

I tried to explain this before, but it seemed no one on here could understand sub-orbital flights of 45 minutes from one side of the planet to the other.

Perhaps you have just done a better job of explaining it than I did.

Perhaps. It should be abundantly clear that starships (even 6g ones) cannot travel at ridiculously high mach numbers except at the upper limits of the atmosphere where there is very little resistance. The charts, as written, are highly misleading. This has always been a complaint I've had with rulebooks that leave it vague and ill or undefined. The reality should be much more nuanced - that starships travel at subsonic speeds when entering or leaving the stratosphere and below. This still works for planets with denser atmospheres. And for simplicity sakes you can use the MT forumula by adding / reducing overall speed by 25% once you start going into thin/dense atmospheres.

There are also limitations to the high-speeds, such as very large turning radius that any craft has to deal with, so point to point will often be very predictable straight lines (in as much as you can do when travelling around the globe). Depending on how you play and to what level of detail this may not be an issue for many. Others may be looking for such definitions as it's going to be part of their game. It's always nice to have such things pre-defined or worked out ahead of time.