I have come to the conclusion that my Grav survey ships are way too large to be efficient surveyers.
Starting tech was nuclear pulse engines, Adv Grav sensors, and Composite armor.
So these designs were possible, to work with my size 60 survey tenders that travel at 3333 km/s.
Survey Grav small class Survey Ship 1650 tons 150 Crew 331 BP Signature 33-120
3636 km/s Armour 1 Shields 0-0 Sensors 1/0/2/0 Damage Control 0-0
Replacement Parts 5
Nuclear Pulse Engine EE0.8 AR-0 (3) Power 40 Engine Efficiency 0.80 Armour 0 Exp 5%
Fuel Capacity 50,000 Litres Range 163.6 billion km (520 days at full power)
Advanced Gravitational Sensors (1) 2 Survey Points
Survey Grav class Survey Ship 2400 tons 240 Crew 549 BP Signature 48-160
3333 km/s Armour 1 Shields 0-0 Sensors 1/0/4/0 Damage Control 0-0
Replacement Parts 10
Nuclear Pulse Engine EE0.8 AR-0 (4) Power 40 Engine Efficiency 0.80 Armour 0 Exp 5%
Fuel Capacity 100,000 Litres Range 225.0 billion km (781 days at full power)
Advanced Gravitational Sensors (2) 4 Survey Points
Survey Grav large class Survey Ship 3000 tons 285 Crew 740 BP Signature 60-200
3333 km/s Armour 1 Shields 0-0 Sensors 1/0/6/0 Damage Control 0-0
Replacement Parts 10
Nuclear Pulse Engine EE0.8 AR-0 (5) Power 40 Engine Efficiency 0.80 Armour 0 Exp 5%
Fuel Capacity 50,000 Litres Range 90.0 billion km (312 days at full power)
Advanced Gravitational Sensors (3) 6 Survey Points
I started with the 2 survey sensor design in the middle, and I am currently building the middle one.
But then I did some measurements.
In the Sol system, the distance between Survey locations in the inner ring is about 2 billion km. The distance for the middle ring is about 2.1 billion km, and for the outer ring approximately 3.1 billion.
The three designs, assuming some number of Survey +10 and +20 officers are available, would complete a survey location in 200 hours, 80 hours (assuming +20 survey leader) and 57 hours.
The travel speeds per hour are:
Small survey ship: 13.09 m km/s
Survey standard and large: 12 m km/s
That means that their travel times are:
Small survey ship, inner ring 152.8 hours middle ring 160.4 hours and outer ring 236.8 hours
The other survey ships would take 166.7 hours, 175 hours, and 258.3 hours
That means the total survey time required for moving to one survey location and surveying it would be:
Small survey, inner ring 352.8 hours, 360.4 hours, and 436.8 hours
Standard survey, inner ring, 246.7 hours, 255 hours, and 318.3 hours
Large survey, inner ring 223.7 hours, 232 hours, and 315.3 hours
There are 6 inner ring, 12 middle ring, and 12 outer ring survey locations per system.
Upgrading to the large survey ship design, with 3 adv grav sensors, is clearly foolish until better engines are developed.
At a ratio of 331 BP to 549 BP or 1: 1.66 the smaller Grav survey ship design is more cost efficient even than the "standard" 2 sensor design for the inner ring. 352.8/246.7 = 1.43
That is, the smaller ship takes 1.43 times as long but costs only 1.66 times as much. And for the outer ring the advantage is significantly greater, with a time ratio of 436.8/318.3, the small cheap design takes 1.37 times as much time.
Some other notes:
Increasing the armor technology makes smaller ships more viable, because the armor is a larger percentage of their mass, and they benefit more from it being reduced.
The "Standard" ship design has a couple of things going for it, more spares/HS, bigger bunker, and it is the exact speed of my tenders, but the large survey ship seemed like a good idea, but I just junked it as if it were a prestige project or a major piece of pork.
The small design may be a little less fuel efficient. It will use less fuel per survey location, but more fuel travelling to the system to be surveyed, when calculated by build points.
For Ion Drives, the cost ratios of the ships are slightly closer, and the travel times are shorter, both work against the 1 sensor design.
