Makes empty internal tanks printable

code/game/objects/items/tanks/tank_types.dm

@@ -93,11 +93,13 @@
 		F.update_icon()
 	else
 		return ..()
+//Makes empty oxygen tanks spawn without gas
+/obj/item/tank/internals/plasma/empty/populate_gas()
+	return
 
 /obj/item/tank/internals/plasma/full/populate_gas()
 	air_contents.gases[/datum/gas/plasma] = (10*ONE_ATMOSPHERE)*volume/(R_IDEAL_GAS_EQUATION*T20C)
 
-
 /*
  * Plasmaman Plasma Tank
  */
@@ -130,6 +132,7 @@
 	air_contents.gases[/datum/gas/plasma] = (10*ONE_ATMOSPHERE)*volume/(R_IDEAL_GAS_EQUATION*T20C)
 	return
 
+//makes empty plasma tanks spawn without gas.
 /obj/item/tank/internals/plasmaman/belt/empty/populate_gas()
 	return
 

code/modules/research/designs/misc_designs.dm

@@ -707,3 +707,57 @@
 	build_path = /obj/item/clothing/gloves/tackler/rocket
 	category = list("Equipment")
 	departmental_flags = DEPARTMENTAL_FLAG_SECURITY
+
+/////////////////////////////////////////
+/////////////Internal Tanks//////////////
+/////////////////////////////////////////
+
+/datum/design/oxygen_tank
+	name = "Oxygen Tank"
+	desc = "An empty oxygen tank."
+	id = "oxygen_tank"
+	build_type = PROTOLATHE
+	materials = list(/datum/material/iron = 2000)
+	build_path = /obj/item/tank/internals/oxygen/empty
+	category = list("Equipment")
+	departmental_flags = DEPARTMENTAL_FLAG_ENGINEERING
+
+/datum/design/plasma_tank
+	name = "Plasma Tank"
+	desc = "An empty plasma tank."
+	id = "plasma_tank"
+	build_type = PROTOLATHE
+	materials = list(/datum/material/iron = 2000)
+	build_path = /obj/item/tank/internals/plasma/empty
+	category = list("Equipment")
+	departmental_flags = DEPARTMENTAL_FLAG_ENGINEERING
+
+/datum/design/emergency_oxygen
+	name = "Emergency Oxygen Tank"
+	desc = "A small emergency oxygen tank."
+	id = "emergency_oxygen"
+	build_type = PROTOLATHE
+	materials = list(/datum/material/iron = 1000)
+	build_path = /obj/item/tank/internals/emergency_oxygen/empty
+	category = list("Equipment")
+	departmental_flags = DEPARTMENTAL_FLAG_ENGINEERING
+
+/datum/design/plasma_belt_tank
+	name = "Plasmaman Belt Tank"
+	desc = "A small tank of plasma for plasmamen."
+	id = "plasmaman_tank_belt"
+	build_type = PROTOLATHE
+	materials = list(/datum/material/iron = 1000)
+	build_path = /obj/item/tank/internals/plasmaman/belt/empty
+	category = list("Equipment")
+	departmental_flags = DEPARTMENTAL_FLAG_ENGINEERING
+
+/datum/design/emergency_oxygen_engi
+	name = "Engineering Emergency Oxygen Tank"
+	desc = "An emergency oxygen tank for engineers."
+	id = "emergency_oxygen_engi"
+	build_type = PROTOLATHE
+	materials = list(/datum/material/iron = 1000)
+	build_path = /obj/item/tank/internals/emergency_oxygen/engi/empty
+	category = list("Equipment")
+	departmental_flags = DEPARTMENTAL_FLAG_ENGINEERING

code/modules/research/techweb/nodes/engineering_nodes.dm

@@ -42,6 +42,14 @@
 	design_ids = list("smes", "super_cell", "hyper_cell", "super_capacitor", "superpacman", "mrspacman", "power_turbine", "power_turbine_console", "power_compressor", "circulator", "teg")
 	research_costs = list(TECHWEB_POINT_TYPE_GENERIC = 3000)
 
+/datum/techweb_node/int_tank
+	id = "int_tank"
+	display_name = "Internal Tanks"
+	description = "How to compress air into smaller containers."
+	prereq_ids = list("engineering")
+	design_ids = list("oxygen_tank", "plasma_tank", "emergency_oxygen", "emergency_oxygen_engi", "plasmaman_tank_belt")
+	research_costs = list(TECHWEB_POINT_TYPE_GENERIC = 2500)
+
 /*
 /datum/techweb_node/basic_meteor_defense
 	id = "basic_meteor_defense"