Ellis' Star: A Bizarre but Necessary Error

The Source Material 

Very recently (i.e. today, as of posting), I've realised there is another error in the 2300AD near star list. It is not the first, and several of these errors have become necessary for the universe (such as Queen Alice's Star). This is one of those.

Ellis orbits Gliese 623. This is now known to be a binary system with two red dwarves orbiting their mutual barycentre 1.9 AU apart. This means no planets can exist in the notional habitable zones. However, the second star of the pair wasn't reported until 1989, and the Gliese catalogue GDW used lists the star as an M3V, i.e. a red dwarf (by the standard tables, 0.36 solar masses and 0.016 solar luminance). However, look at the 1st edition NSL entry:

 

It is listed as a G0V star (1.04 solar masses, 1.21 solar luminosity by the GDW tables), not a red dwarf.

The Colonial Atlas entry is by William Connors, and says the star is a M3VI, with a mass of 0.013 solar masses and a luminosity of 0.0065. This is a problem. The listed mass is 13.6 Jupiter masses, i.e. a brown dwarf. It is not either the NSL yellow star, or the source material M3V. The luminosity is a nonsense, as the BD is just on the limit of deuterium fusion, and this would have been expended very early in the BD's life (about 10 million years after formation), leaving a large gas giant.

There is no possibility of any habitable planet in such a system. Ellis is listed as orbiting at 0.07 AU (~ 10 million km), which means it would get 1.33 times the insolation of Earth whilst the deuterium lasted (using the write-up luminosity), but then would go dark. It would entirely be infrared to dull red, with no green or blue light to sustain photosynthesis.

In a further wrinkle, the 2300AD Resource, which is also considered canon, places Ellis as 0.013 AU from the star, and the shelf at 0.28 AU, which makes the stellar mass 0.08 of Sol. This would be an M9V star, large enough to sustain hydrogen fusion, giving an insolation of 0.05 of Earth.

Then there's the 1988 boxed set, which says:

 

Yet another stellar type! Now Ellis' star is a G8V (i.e. a yellow dwarf slightly smaller than Sol, 0.93 solar masses and 0.63 solar luminescence by standard tables). Yet, and the same time the NSL entry in the 1988 edition was edited to match the Colonial Atlas writeup!

  

 

The Fix

What to do in this bizarre situation?

Firstly, let us observe that every single listing for Ellis' star type is wrong. Secondly, we cannot use the real system, because a planet is impossible. Thirdly, we want to sustain the existence of the planet as described in "Liberty."

The best answer to to accept the 1988 writeup, and have that override Connors' mess. The planet Ellis would orbit about 0.8 AU, giving similar insolation to Earth. Oyster would be about 1.6 AU, and Gibbet about 3 AU. The FTL shelf is about 2.36 AU out, and so visiting Ellis, which is too dangerous to orbit, means taking a ship to Boise (near Oyster), and then making a 0.8 AU journey. This would be perfect for a stutterwarp equipped lander, and would justify America building such things.

How the AEH Broke 2300AD Starshios

This has been sitting around incomplete for three years. I need to reference it, and so I'm hitting publish.

Power

As I've previously noted, the conversion of power points to wattage is wrong.

In Mong Traveller 2nd edition High Guard, power was abstracted into power points. Reading the speculation of players, they thought each Traveller energy point (EP) was 250 MW, which was from DGP works. 

Checking GDW High Guard, no figure is given. Power plants output ca. 1-6 EP per 100 dTons of ship, depending. It took 3 dTons to produce 1 EP at TL9-12.

Striker gives output in MW/m3. It gives fusion producing 2 MW per m3 at TL 9-12 fusion. This makes an EP ca. 84 MW.

Megatraveller gave energy points as "250 Mw," and they put "megawatts" in scare quotes in places, indicating these aren't real megawatts. Thus we have real megawatts ("MW") and MT pseudo-megawatts ("Mw").

The charts in Megatraveller can be compared to those in Striker, and for the fusion reactors the values are identical. Thus, the listed outputs in Megatraveller are for MW. In both Striker and Megatraveller, 1 m3 of fusion reactor has an output of 2 MW. The same value appears in TNE. This is actually a ludicrously high output.

However, looking at the black globe rules, it is clear that the Mw is not the same as MW. The Mw is a unit of energy, not power. It's likely a Mw is a MW-turn.

Cuberoot vs Squareroot

The stutterwarp formula in all editions until the 5th (2nd Mongoose) had stutterwarp efficiency being proportional to the cuberoot of the power/mass ratio. It was indicated by the author of the Mongoose edition, on 12th August 2016, that the Aerospace Engineer's Handbook was almost done, that the stutterwarp formula still used the cuberoot equation of all previous editions and Fire, Fusion and Steel. However, the Mongoose author noted that the editor hated formulae. They wanted everything to be tables.

The Mongoose author then opined he thought the cuberoot formula produced a "very odd performance curve." Sadly, I did not see it at the time, because he was wrong. The cuberoot formula is the correct one from the physics point of view.

The cuberoot formula applies to wet ships on the oceans. This is because speed is proportional to propeller speed, and the propeller speed is proportional to the cuberoot of the power put into it. The reason this is a cubic relationship is because the resistance of a medium to displacement (such as turning a piston stroke into a propeller turning) is equal to the velocity of the displacement (i.e. the work) * the square of the velocity (i.e. 1/the resistance to work). It is almost universal, and applies also to aircraft - everything else being equal, an aeroplane requires 8 times the power to double its' speed. It applies to cars (automobiles). It applies to everything where there is a resistance to the change in velocity, and stutterwarp drives do have rotary motion at their heart (hence the pseudomomentum and pseudovelocity).

It does not apply to rockets in a vacuum, who have a squareroot relationship. They have, assuming keeping the reaction mass constant (in an ion drive etc.), a square relationship of acceleration to power. It takes a 4-fold increase in engine power to double the exhaust velocity and hence the acceleration. 

The Change

At some point after this, the AEH adopted a rather strange formula that use a squareroot, but also much higher warp multipliers. The general formula, based on GDW's Fire, Fusion & Steel conversion to dTons is:

Warp Efficiency = TLM * (power (MW)/ 10 * displacement) ^1/x 

The resulting warp multipliers, after factoring out the power multiplier and halving of mass are:

Note that in GDW Traveller conversions, the TL is one higher. Also note that in March '22 a new correction has made (to counter my point about the Kennedy being slowed) and the original TLM's are now in force (recalculate, everyone who made ships in the interim). This is because I pointed out that the Kennedy's speed needs recalculating, as it was then warp 3.6.

Further, power is much cheaper with respect to displacement. This made it ridiculously easy to get to much higher speeds. I pointed out that if you built a Kennedy using the same basic design as the GDW Kennedy, it would be going warp 15.3, a much higher number. The reaction to this was the December revision, in which the warp multipliers were slightly lowered, and a warp speed limit based on TL imposed. This was a very crude fix, that actually fixed nothing. When I queried this, the author stated it was too much bother to correct, or words to that effect (I am blocked from the thread and can't see it). A new revision  was made simply adding speed limits.

The Kennedy was written as if the speed were 4.83, and this is the stated speed in the AEH writeup. However, that speed is from a pre-Alpha version, and the speed of the Kennedy as of the December '21 revision is 3.58, and this is regarded as a very fast ship.

This has created problems for designers who are desperate not to go faster than the Kennedy. Going faster than the Kennedy is trivial, because the spirit of the Kennedy has not been preserved. Indeed, I have made an Mongoose Kennedy using GDW rules, and I have a cheap patrol cruiser which is outpaced by a light fuelled Aconit (see Appendix 1).

Fixing Stutterwarp

Firstly, the equation must be cubic, or things break down quickly. Secondly, the TLM must be lower than GDW to compensate for the more abundant power. 

The Kennedy as presented was a light ship, and indeed unrealistically light. The Kennedy should get around warp 4.47 with 55.56% of the ship being reactor, fitting the AEH's author's statement in 2016 that "The Kennedy is a reactor with a small ship attached." He also stated it's the spirit of the ship that matters, rather than the conversion. The spirit of the Kennedy was a ship-killer built entirely around being mostly reactor, with a weak armament but a reasonable complement of missiles.

Keeping with the mass fraction, 500 of the 900 dTons should be reactor. That's 750 MW with advanced fusion and 600 MW with simple fusion. The Kennedy may well be a simple fusion vessel, as she's Americas' first fusion powered vessel. Solving and rounding to the nearest 0.5 gives a multiplier of 11 (as a simple fusion vessel). In fact, a TLM of TL-1 works quite well.

Thus herein is a revised equation.

 

Where TL is the tech. level, P is power in "power" (i.e. units of 100 kW) and T is tonnage in dTons.

The Mongoose Kennedy is, of course, not a fast ship. The warp efficiency resolves to 1.8. This is because the "spirit" of the Kennedy is not preserved in the Mongoose version.

Remaking the Kennedy

By the volume fraction, 40% of the GDW Kennedy is reactor, or 360 dTons. This is a 432 MW simple fusion reactor.

The issue is, of course, that the Kennedy does need an actual redesign. To fit the spirit of the Kennedy, the fusion reactor needs to be a large chunk of the ship, otherwise someone else can simply up their fraction to drive and the Kennedy is slow. 

However, when I looked at the MgT deckplans, I found they were for a 1,250 dTon vessel, with a ca. 350 dTon fusion reactor. This absolutely fits the "spirit" of the GDW design. The original GDW version omitted the spin habs. We could make a reasonable facsimile of the GDW Kennedy using the deckplans.

It should be noted, the accommodation habitats do not match the exterior. The habitats viewed from the exterior are only 2 decks high, whereas the deckplans are for 4 decks high. This would make them "square" from the back, being as high as broad (i.e. 12 m x 12 m x 18 m long). This is correct because the MgT ship has twice the size of accommodations of the GDW ship (5,184 m3 vs just over 2,500 m3). Approximately 370 dTons are in the two habitat modules. There is ca. 55 m3 per person in the habitat modules, which, after noting the medical stations would be under spin etc., is twice the volume per person as in the GDW ship. Hence the accommodations being twice the size.

The rest prettymuch matches, although it should be noted that the missile launchers physically can only fit 5 MgT SIM-14 each, and the guns are badly placed. The guns have been placed on the forward slope of the aft section, behind and beneath the spin capsules. They have no arcs to the rear, and they will lik

Appendix 1: Mongoose-Kennedy class missile cruiser remade using GDW rules

Notes: This is the Kennedy of MgT 2k3 2e (5^th edition) converted back to GDW Star Cruiser. It’s an exercise in see how well the “spirit” of the Kennedy was retained. The decision was made to replicate the volumes of the major features. The SIM-14 used is that of GDW (i.e. 1 dTon per missile). The important thing is to reproduce the spirit of the Mongoose Kennedy with GDW rules.

The power plant is too small to be a fusion reactor. Ergo it must be a fission reactor. The amount of power used in the stutterwarp was rescaled to the increase in PP output on MgT. The result is that the Mongoose compliant Kennedy has a 10 MW stutterwarp. Given the history, the early Kennedy class were built with a OC drive, but in 2295 a new NM drive was created, and the fleet was retrofitted. The guns are EA-1000, i.e. x2+1, using 2 MW each. There are nine of them for 18 MW power usage (28 MW total). The active sensor requires 7 MW, giving a total of 35 MW.

The major features added in MgT were an increase in the accommodation, and a large quantity of reaction mass. The volume of the accommodations and other things carried under it in GDW is 369.4 dTons (5,171.6 m3). Keeping this roughly constant would mean having double accommodations (4,500 m3) plus spin, l.s. etc., which gives a similar volume. The ship has a 10 MW MHD thruster, with reaction mass totalling 24% of the volume, at 3% of volume per “burn”.

The hull is kept identical to the GDW original, but is made from advanced synthetics. The masking is now basic, in line with the MgT radiators.

Comparing the GDW original and the MgT conversion, the latter is clearly a much cheaper and less capable ship. The original gave just over 40% of its’ volume to the power plant, and about half its’ mass in a combat state (i.e. ca. 10,000 metric tons, move 8), but notably had the vast majority of the power plant is used to power the stutterwarp in action. Compare to the MgT Kennedy, where only half the power is actually used at any one time.

 

Performance

• Warp efficiency: 1.91 unloaded
• Power Plant: 35 MW fission
• Fuel: 2,096.394 tons (reaction mass plus 5x refuels for drone)
• Range: 7.7 light years
• Endurance: 56 days
• Mass: 7,633 tons unloaded
• Cargo Capacity: 235 cubic meters
• Crew: 84 (16 Bridge, 22 TAC, 4 Small Craft, 28 Engineering, 10 troops, 9 stewards, 3 medical); Passengers: upto 6
• Comfort: +1;
• Emergency Power: -
• Total Life Support: 90 for 56 days
• Cost: MLv 66.8 bare, MLv 205 of ordnance carried 

Ship Status Sheet

• Move: 4
• Screens: 0
• Radiated Signature: 5(6)
• Radial Reflected: 5
• Lateral Reflected: 7
• Target Computer: +2 (one target);
• Radial Profile: 0
• Lateral Profile: +2
• Armour: 0
• Hull hits: 20/10/5 (SC formula)
• Power Plant Hits: 44/8
• Active: 15
• Passive: 10

Other:

Weapons

9 x2+1 lasers in masked turrets with UTES (4x 1234, 4x 1678, 1x 4567)

Ordnance Load

·       2 Missile Launchers, each with 10 SIM-14 missiles (launch 2 missiles/turn total)

·       HD-5 drone in minimal hangar (5 turns to launch)

Sensors and Electronics:

Active-15
Passive-10
Navigation Radar
DSS
Gravitational

Crew Hits:
Bridge: Captain, Navigator, Helm, Communications, 4 Computer
TAC: 9 Fire Control, 10 Remote Pilot, 1 Flight Control, Active Operator, Passive Operator,

Damage Control: 14 (5 teams)

Appendix 2: OMS Thrusters

Simple physics is such that to change momentum in space, one just apply an equal and opposite force. The energy of the momentum change is the first integral of it. So the dV is proportional to exhaust velocity which is proportional to the squareroot of the energy used to propel the exhaust.

An electromagnetic hydrodynamic rocket works by burning hydrogen and oxygen together, but then instead of extracting energy from the initial plasma through a coil, energising the coil and using this to accelerate the exhaust. It's a halfway house between a conventional rocket and an ion-drive. The exhaust is already 4.4 kps, and the additional electricity boosts the velocity, increasing dV. However, the power for an OMS is very low, and this means that there is essentially no boost with a high fuel consumption rate.

The Kennedy uses 8.1 dTons per burn, or 4.91 metric tons of reaction mass. The momentum change without additional energy is thus 21,600 t.m.s-1, or a velocity change of 2.4 m.s-1. Yes, 2.4 meters per second. To address this, we dump electrical power into the drive, and the OMS of the Kennedy uses 9 MW. If we assume 100% efficiency, then lengthening the burn to a day (56 grams of fuel per second burnt) gives 5.6 m.s-2, which is more than double the dV. This is probably about the limit with an electromagnetic thruster, since we need a certain minimum rate of burning to generate a plasma. To get 1 kps dV we'd have to lower the burn rate to just over a year. At this point, a true ion-drive becomes more efficient.

This thruster wouldn't need to be very large at all. It could be a few kg.

Whilst MgT 2k3 assiduously avoids stating what a "burn" is, I can do basic maths. A "burn" is approximately a dV of 100 mps when calculated from the drive's thrust, but 1.5 kps when calculated from the thrust effect (i.e. a difference of 15,000x). When using the Kennedy's OMS thruster, the length of time needed for said burn is on the order of one month, because the amount of power being put into the fuel is tiny (9 MW), and hence the fuel expenditure needs to be at a low rate to allow the exhaust to be accelerated by the power plant.

Meanwhile, GDW ships made some quite large velocity changes by diving past planets, entering the dead zone (which is, by definition, accelerating them < 0.1 G). This is vastly more useful than the MgT OMS thrusters, which are essentially useless.