A H-to-MWSS is a Spartan (using an Eater 1 instead of the 7x9 eater) converter found by Tanner Jacobi in October 2015, which converts an input Herschel to a middleweight spaceship. The key discovery was a very small but slightly dirty H-to-MWSS conduit, where a Herschel is catalyzed to produce an MWSS but also leaves behind a beehive. Prefixing two R64 conduits to this produces a composite converter that successfully deletes the beehive in advance, using the input Herschel's first natural glider.
The repeat time is 157, but it can be reduced to even 72 using the variant below (or other variants, if not required to be spartan).
x = 179, y = 160, rule = B3/S23
71b2o3bo$72bo2bobo$70bo4bobo$70b5obo$74bo$70b2o3bo15b2o$70bobo3bo14bo$
71bo3b2o12bobo$47bo37b2o2b2o$47b3o35b2o$50bo$33b2o14b2o11b2o11bo$33b2o
27b2o9b3o$73bo$73bo$27b2o$27b2o$31b2o$31b2o15bo$48bo$48b3o40b2o$50bo
22b2o16bobo$26b2o44bobo18bo$26b2o44bo20b2o$71b2o4b2o$46bo3b2o24bobo$
45bobo3bo24bo$45b2o3bo24b2o7b2o$49bo12b2o20b2o$45b5obo10bo$40b2o3bo4bo
bo10b3o$40bo6bo2bobo12bo$38b3o5b2o3bo2$97b2o$47b2ob2o40b2o2bo2bo$46bob
obo2bo38bobo2b2o$47bo2bob2o41b2o$50bo45bo$49b2o42bo2bob2o$46bobo2b2o
39bobobo2bo$46b2o2bo2bo39b2ob2o$51b2o2$84b3o5b2o3bo$86bo6bo2bobo12bo$
86b2o3bo4bobo10b3o$91b5obo10bo$38b2o55bo12b2o$29b2o7b2o51b2o3bo$30bo
60bobo3bo38b3o$30bobo59bo3b2o37bo2bo$25b2o4b2o105bo$26bo20b2o23b2o60bo
3bo$26bobo18bo24b2o64bo$12b2o13b2o16bobo48bo38bobo$12b2o31b2o47b3o$94b
o$77b2o15bo$6b2o69b2o$6b2o65b2o$10b2o61b2o$10b2o15bo91bo$27bo91bo22bo$
27b3o49b2o27b2o9b3ob2o16bobo$29bo49b2o14b2o11b2o11bob2o16bobo$5b2o89bo
45bo$5b2o32b2o52b3o$39b2o2b2o48bo$25bo3b2o12bobo$24bobo3bo14bo$24b2o3b
o15b2o$28bo$24b5obo$19b2o3bo4bobo108bo$19bo6bo2bobo107bobo$17b3o5b2o3b
o108b2o3$26b2ob2o$25bobobo2bo$26bo2bob2o$29bo$28b2o$25bobo2b2o$25b2o2b
o2bo141b2o$30b2o142bo$176bo$156b2o14b5o$157bo13bo$157bobo12b3o$158b2o
15bo$17b2o153b4o$17b2o148b2o3bo3b2o$167b2o4b3o2bo$8b2obo163bob2o$8bob
2o163bo$26b2o146b2o$26bo$24bobo$24b2o140b2o$166bo$9bo157b3o$9b3o157bo$
o11bo$3o8b2o14bo$3bo22bobo$2b2o23bo$76b2o$76bobo$78bo4b2o$74b4ob2o2bo
2bo$74bo2bobobobob2o$77bobobobo$bo76b2obobo$bobo78bo$b3o$3bo11b2o51b2o
$15bo53bo7b2o$16b3o50bobo5b2o$18bo51b2o7$80b2o$80bo$81b3o$83bo6$56bo$
54b3o54bo$53bo55b3o$53b2o53bo$108b2o6$43b2o$42bobo5b2o46b2o$42bo7b2o
45bobo5b2o$41b2o54bo7b2o$96b2o$55bo$51b2obobo53bo$50bobobobo49b2obobo$
47bo2bobobobob2o45bobobobo$47b4ob2o2bo2bo42bo2bobobobob2o$51bo4b2o44b
4ob2o2bo2bo$49bobo54bo4b2o$49b2o53bobo$104b2o!
#C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]]
#C [[ AUTOSTART GPS 60 LOOP 819 THUMBLAUNCH THUMBSIZE 2 THEME 6 ZOOM 4 WIDTH 800 HEIGHT 800 PAUSE 2 T 73 PAUSE 2 T 97 PAUSE 2 T 156 PAUSE 2 T 220 PAUSE 2 T 273 PAUSE 2 T 332 PAUSE 2 T 396 PAUSE 2 T 473 PAUSE 2 T 526 PAUSE 2 T 585 PAUSE 2 T 649 PAUSE 2 T 723 PAUSE 2 T 818 PAUSE 2 ]]
The infobox pattern contains initial ghost Herschels marking the three Herschel (or Herschel great-grandparent) locations in the H-to-MWSS conduit. The pattern also includes a common way of reaching the input Herschel by prepending an Fx77, but that additional conduit is not a necessary part of the H-to-MWSS.
There are many other ways to remove the unwanted beehive using a spare glider or additional conduits, but they are generally less compact than this.