Hello everyone, I came across two things that feel a bit odd: OPT-E J Linear aerospike feels underperforming when compared to other engines: It is set to produce about 100kN per 1t of engine weight, while most stock chemical engines produce between 150-250kN per 1t of weight. In case of Linear aerospike, that's around 4t of extra weight that could be used for cargo or for more fuel, or for secondary set of more efficient engines. In short, currently it's much more efficient to use e.g. two Nebulas paired with two LV-Ns, which will get craft to orbit easily and offer much higher ISP both in atmosphere and in space. I guess considering it's large size, increasing power to match about 200kN/t would be more logical, since it can be replaced by an engine mount with four 1.25 slots which can be used by four Vectors with 4000kN together or by two vectors + two LV-N, still offering significantly more thrust and much more ISP than single Linear aerospike. At 8t and 1600kN it would remain considerably weaker than 2 vectors at same weight (2x4t for 2x1000kN) but more efficient thanks to it's higher ISP. Right now there isn't much use for Linear aerospike besides for streamlined look. Regarding ARI engine, the idea behind it is great, but it could also use a bit of tweaking. Right now, in atmosphere it's simply better to use air breathers and in oxygen-less space like on Duna, an LV-N is usually a much better choice. Aside from EVE or a dedicated Duna glider that never goes to space there isn't much use for ARI. Maybe increasing the flight ceiling for the high efficiency mode? Increasing it's vacuum ISP could render other vacuum engines obsolete, but then again, Making history DLC introduced a 412 vacuum ISP engine, so there may be some room left. Are those two engines working as intended or is it still WIP?