This table just lists the combined weights of thruster+steering for available atomic engine combos, so you can find something that fits in your engine bay & available outfit space. Bear in mind this list is from the point of view of wanting to go as fast/manueverable as possible. Korath (and to a lesser degree Human) engines are less heat/energy efficient, but this list assumes you are willing to deal with the power and cooling requirements to get maximum engine output. While efficiency varies, with Human and Hai atomic engines a heavier part is always also more performant than a light one. This is not true of the Korath; the Korath Stellar parts are better than the heavier A86, the Planetary Steering better than A525, the Lunar Steering better than Biroo. Additionally some Korath parts are extremely close in performance to the next heaviest Human/Hai part. Those Human/Hai parts are listed, but marked po - probably obsolete. These are the A520 thruster, Biroo thruster, and Benga steering. Remnant parts have the best heat efficiency, but the worst energy efficiency; fortunately, access to them comes with access to the high-density Remnant batteries. The Remnant Crucible-class parts render human A12 parts obsolete. The Forge-class parts are the most performant at their weight, but don't beat out any heavier part; furthermore Korath Lunar-class parts offer much better performance for very small weight increases, so Forge-class parts are only desirable if there is no outfit space to spare. Smelter-class parts are outperformed by Korath Planetary-class parts so are not listed. Wanderer parts are both energy and heat efficient, but generally offer poor performance/mass compared to lighter Korath parts. The only two listed are the Type 1 Radiant parts which are smaller than any other available part, and the Type 4 Radiant steering; all of these are desirable only if there is no outfit space for the next largest part. (They are, however, phenomenally heat-efficient because they include cooling, and if you abandon the goal of having as fast a ship as possible, you can use them to effect a huge reduction in outfit mass.) The Coalition complicate matters further because of their modular design; the lack of large parts requires one to consider combinations of smaller parts. Their parts have the best energy efficiency, but terrible heat efficiency; however, they make a highly efficient active cooling module which offers a way to rebalance a ship's heat and energy capacity. Additionally, the smallest Coalition parts are very small indeed, and might be added to a combo of other-faction parts that doesn't quite fill the available space. Many combinations of Coalition parts don't offer higher performance for the mass than existing parts. They are not listed. Coalition Small Modules obsolete Type 1 Radiant Parts. 2 Small Thrust Modules offer the same performance as a Basrem; higher heat, lower energy. Heat dissipation is easier to come by so only the Coalition option is listed. 1 Large Thrust Module makes the Human A250 Thruster "probably obsolete". 1 Large Steering Module does render the Human A255 Steering obsolete. All larger combinations of Coalition thrusters are outclassed by less massive parts from other factions. 1 Large and 3 Small Steering Modules is a viable combination (one tonne lighter than a type 4 Radiant). 3 Large Steering Modules is technically viable but note it is one tonne lighter than a Bufaer with about 2/3 the performance, so only sensible if no more space can be had at all. The bracketed number after each part is the overall tier (eg, "Benga(3)" means there are 2 engines smaller than the Benga, and all others are larger). 16 Both Coalition-Small(0) 19 Coalition-Small(0) thrust, Asteroid(1) steering 21 Asteroid(1) thrust, Coalition-Small(0) steering 21 Coalition-Small(0) thrust, Basrem(2) steering 23 Coalition-Small(0) thrust, Crucible(3) steering 24 Both Asteroid(1) 26 Asteroid(1) thrust, Basrem(2) steering 27 Crucible(3) thrust, Coalition-Small(0) steering 28 Coalition-2Small(4) thrust, Asteroid(1) steering 28 Asteroid(1) thrust, Crucible(3) steering 30 Crucible(3) thrust, Asteroid(1) steering 30 Coalition-2Small(4) thrust, Basrem(2) steering 32 Coalition-2Small(4) thrust, Crucible(3) steering 32 Crucible(3) thrust, Basrem(2) steering 34 Both Crucible(3) 36 Coalition-2Small(4) thrust, Comet(5) steering 36 Comet(5) thrust, Basrem(2) steering 38 Crucible(3) thrust, Comet(5) steering 38 Coalition-2Small(4) thrust, Benga(po)(6) steering 38 Comet(5) thrust, Crucible(3) steering 40 Crucible(3) thrust, Benga(po)(6) steering 42 Benga(6) thrust, Crucible(3) steering 42 Both Comet(5) 43 Coalition-2Small(4) thrust, Coalition-Large(7) steering 44 Comet(5) thrust, Benga(po)(6) steering 46 Benga(6) thrust, Comet(5) steering 48 Both Benga(po)(6) 49 Comet(5) thrust, Coalition-Large(7) steering 50 Coalition-Large(7) thrust, Comet(5) steering 52 A25(po)(8) thrust, Comet(5) steering 52 Coalition-Large(7) thrust, Benga(po)(6) steering 53 Benga(6) thrust, Coalition-Large(7) steering 54 A25(po)(8) thrust, Benga(po)(6) steering 56 Benga(6) thrust, Forge(9) steering 57 Both Coalition-Large(7) 59 A25(po)(8) thrust, Coalition-Large(7) steering 59 Forge(9) thrust, Benga(po)(6) steering 60 Coalition-Large(7) thrust, Forge(9) steering 62 A25(po)(8) thrust, Forge(9) steering 62 Coalition-Large(7) thrust, Lunar(10) steering 64 A25(po)(8) thrust, Lunar(10) steering 64 Forge(9) thrust, Coalition-Large(7) steering 65 Lunar(10) thrust, Coalition-Large(7) steering 67 Both Forge(9) 68 Lunar(10) thrust, Forge(9) steering 69 Forge(9) thrust, Lunar(10) steering 70 Both Lunar(10) 72 Biroo(po)(11) thrust, Forge(9) steering 74 Biroo(po)(11) thrust, Lunar(10) steering 77 Forge(9) thrust, A37(12) steering 78 Lunar(10) thrust, A37(12) steering 81 A37(12) thrust, Forge(9) steering 82 Biroo(po)(11) thrust, A37(12) steering 83 A37(12) thrust, Lunar(10) steering 86 Lunar(10) thrust, Coalition-1L3S(13) steering 90 Biroo(po)(11) thrust, Coalition-1L3S(13) steering 91 Biroo(po)(11) thrust, 4-Radiant(14) steering 91 Both A37(12) 99 A37(12) thrust, Coalition-1L3S(13) steering 100 A37(12) thrust, 4-Radiant(14) steering 101 Bondir(15) thrust, A37(12) steering 102 A37(12) thrust, Bondir(15) steering 109 Bondir(15) thrust, Coalition-1L3S(13) steering 110 Bondir(15) thrust, 4-Radiant(14) steering 112 Both Bondir(15) 115 Planetary(16) thrust, Coalition-1L3S(13) steering 115 Bondir(15) thrust, Planetary(16) steering 116 Planetary(16) thrust, 4-Radiant(14) steering 118 Planetary(16) thrust, Bondir(15) steering 121 Both Planetary(16) 129 A52(po)(17) thrust, 4-Radiant(14) steering 131 A52(po)(17) thrust, Bondir(15) steering 134 A52(po)(17) thrust, Planetary(16) steering 138 Bondir(15) thrust, Coalition-3Large(18) steering 144 Planetary(16) thrust, Coalition-3Large(18) steering 145 Planetary(16) thrust, Bufaer(19) steering 156 Bufaer(19) thrust, Planetary(16) steering 157 A52(po)(17) thrust, Coalition-3Large(18) steering 158 A52(po)(17) thrust, Bufaer(19) steering 171 A52(po)(17) thrust, Stellar(20) steering 179 Bufaer(19) thrust, Coalition-3Large(18) steering 180 Both Bufaer(19) 193 Stellar(20) thrust, Coalition-3Large(18) steering 193 Bufaer(19) thrust, Stellar(20) steering 194 Stellar(20) thrust, Bufaer(19) steering 207 Both Stellar(20)