Loren was anxious about glaring errors in MegaTraveller.
Here is an excerpt from some of the stuff which I am
preparing which points out the errors in the design construction
rules.
MEGATRAVELLER DESIGN CONSTRUCTION REVIEW PART 2
DESIGN EVALUATION
Maximum Speed:
In MegaTraveller, the thrust/weight ratio and it's correspondance
to maximum speed is way off. Below is a list of aircraft and their
maximum speed listed aside their thrust/weight ratio.
(all speeds below are in kilometers per hour)
Thrust/Wt Aircraft Speed MegaT COACC
0.2G C-135A 965 240 240
0.3G A-6 1100 360 360
0.4G F-5 1700 480 480
0.5G F-8 1930 600 600
0.6G F-105 2235 720 720
0.7G F-106 2455 840 840
0.8G F-14 2485 960 960
0.9G 1080 1080
1G F-15 2655 1200 1200
2G 2120 2000
3G X-15 7274 2850 3000
4G 3400 3200
5G 3840 3750
6G 4200
(the SR-71's thrust to weight ratio is 0.3824. Max speed is
unknown but around 3100kph)
In the light of the above, grav vehicles and starships max speed
should be vastly higher than they are. Any 1G merchant ship should
be about Mach 2+, and any grav vehicle/ship with an excess thrust
of 3G would be about as fast as the X-15. (Mach 6+!)
I therefore suggest the following table for evaluation of thrust vs
maximum speed. For Grav vehicles and spacecraft, unstreamlined
hulls would be treated as Simple airframes, streamlined would be
treated as transonic and airframe hulls would be treated as
hypersonic.
These limits apply only to craft while within an atmosphere.
AirFrame Type
Thrust/Wt Simple Subsonic Transonic Supersonic Hypersonic
0.1G 105 110 840 900 1500
0.15G 155 160 900 950 1750
0.2G 205 215 960 1000 2000
0.25G 255 270 1000 1200 2250
0.3G 300 325 1060 1400 2500
0.35G ^ 380 1100 1600 2750
0.4G ^ 430 1115 1800 3000
0.45G ^ 490 ^ 2100 3250
0.5G ^ 540 ^ 2200 3500
0.6G ^ 650 ^ 2300 4000
0.7G ^ 760 ^ 2400 4200
0.8G ^ 800 ^ 2500 4400
0.9G ^ ^ ^ 2600 4600
1G ^ ^ ^ 2800 4800
2G ^ ^ ^ ^ 5000
3G ^ ^ ^ ^ 7000
4G ^ ^ ^ ^ 9000
5G ^ ^ ^ ^ 10,500
6G ^ ^ ^ ^ 11,000
As this table will greatly increase the speed of aircraft, the
thrust tables of the available aircraft engines will have to be
reduced to suit it. This will have the effect of keeping the
aircraft within reasonable limits in terms of speed. However, it
will have the effect of requiring large or multiple engines for
VTOL aircraft. This is consistant with reality however. VTOL
aircraft are VERY complex and COACC does not aedequately reflect
this.
VTOL Aircraft must suffer some thrust penalties due to the nozzles
necessitated by their VTOL design. As all VTOL aircraft must have
a thrust to weight ratio greater than one, one would expect from
the table above that all VTOL aircraft would be extemely fast. As
this is not the case, forward thrust for the aircraft must be
divided by 4. Thus, the Harrier with it's Thrust/Wt of 1.227 would
have a modified thrust in forward flight of .307 and would (with
her transsonic airframe have a top speed of 1060kph. This penalty
could be overcome by the use of dedicated lift engines. This type
VTOL aircraft would have at least 2 engines. One to get her off
the ground (with a thrust to weight ratio of 1+) and one to propel
the aircraft in forward flight.
(Note: I'm not really happy about the subsonic and simple airframe
data up there. The data I've been looking at has no thrust data for
me to use to compute it from, it's all in horsepower. I will probably
change things around later.)
(Also note: The above tables require a major rewriting of the COACC
engines. The thrust must be reduced substantially from that given in
COACC. This will be addressed later)
Scott 2G Kellogg