diff --git a/src/game.cpp b/src/game.cpp
index b72fd04..bc5bc1f 100644
--- a/src/game.cpp
+++ b/src/game.cpp
@@ -52,6 +52,25 @@ disableGameOrbit(GameState* gs, GameOrbit* orbit)
 	*orbit = {0};
 }
 
+double
+getTimeStep(GameState* gs)
+{
+	u64 last_sdl_tick = gs->game_time_ms;
+	gs->game_time_ms = SDL_GetTicks64();
+	u64 current_tick = gs->game_time_ms - last_sdl_tick;
+	double time_step = 0;
+
+	// NOTE: update sim time base on time since last frame * sim_speed
+	if (gs->running) {
+		u64 last_game_tick = gs->sim_time_ms;
+		gs->sim_time_ms = gs->sim_time_ms + current_tick * gs->sim_speed;
+		u32 diff_ms = gs->sim_time_ms - last_game_tick;
+		time_step = double(diff_ms) / 1000;
+	}
+
+	return time_step;
+}
+
 Ellipse3D
 ellipse3DInit(EllipseParameters ep, uint vert_count)
 {
diff --git a/src/game.h b/src/game.h
index c79fcc4..e5115c3 100644
--- a/src/game.h
+++ b/src/game.h
@@ -65,6 +65,8 @@ GameOrbit* getSelectedOrbit(GameState* gs);
 
 void disableGameOrbit(GameState* gs, GameOrbit* orbit);
 
+double getTimeStep(GameState* gs);
+
 // NOTE: create vertices for a 3d ellipse
 // 	all vertices are in the x/y plane with z = 0
 Ellipse3D ellipse3DInit(EllipseParameters ep, uint vert_count);
diff --git a/src/main.cpp b/src/main.cpp
index 8248362..1ff3b36 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -215,6 +215,23 @@ loadScene(GameState* gs, RenderState* rs)
 	return true;
 }
 
+void
+processInput(RenderState* rs)
+{
+	static InputState is = {};
+	SDL_Event e;
+	bool gooey_wants = false;
+
+	while (SDL_PollEvent(&e)) {
+		// FIXME: we should check for escape key here first
+		gooey_wants = gooProcessEvent(e);
+		if (!gooey_wants) inputProcessEvent(&is, e);
+	}
+
+	if (is.window_closed || is.escape)
+		rs->running = false;
+}
+
 void
 updateSatelliteModel(TwoBodySystem& sys, double time_step)
 {
@@ -235,67 +252,35 @@ updateSatelliteEntity(Entity* e, const Satellite& sat)
 	setEntityPosition(e, xform * vec4(v.x, v.y, v.z, 1));
 }
 
-// NOTE: use ellipseValidate(ep) before calling to avoid failing assertions
 void
-updateOrbit(TwoBodySystem sys, Entity& ellipse_entity)
+updateOrbit(GameOrbit* orbit, bool running, double time_step)
 {
-#if 0
-	ellipse3DUpdate(sys.ep, sys.e3d);
-
-	for (uint i = 0; i < sys.e3d.vert_count; i++)
-		ellipse_entity.mesh->vertices[i] = sys.e3d.vertices[i];
-
-	entUpdateSimpleMesh(ellipse_entity, ellipse_entity.mesh, GL_LINE_LOOP);
-#endif
+	assert(orbit);
+
+	if (running && orbit->in_use) {
+		double previous_true_anom = orbit->system.sat.theta;
+		updateSatelliteModel(orbit->system, time_step);
+		updateSatelliteEntity(orbit->satellite_entity, orbit->system.sat);
+
+		if (testManeuverStep(orbit->maneuver,
+					previous_true_anom,
+					orbit->system.sat.theta))
+		{
+			applyManeuver(orbit);
+		}
+	}
 }
 
-// FIXME: this needs some helpers
 void
 preFrameCallback(RenderState* rs, void* user_data = nullptr)
 {
-	static InputState is = {};
-	SDL_Event e;
-	bool gooey_wants = false;
-
-	while (SDL_PollEvent(&e)) {
-		// FIXME: we should check for escape key here first
-		gooey_wants = gooProcessEvent(e);
-		if (!gooey_wants) inputProcessEvent(&is, e);
-	}
-
-	if (is.window_closed || is.escape)
-		rs->running = false;
-
-	// TODO: sim time stuff should have dedicated functions, and maybe a test
-	// 	since it's pretty important that the simulation is accurate-ish
-	// TODO: verify time to apoapsis/periapsis are correct
+	processInput(rs);
 	assert(user_data != nullptr);
 	GameState* gs = (GameState*) user_data;
-	u64 last_sdl_tick = gs->game_time_ms;
-	gs->game_time_ms = SDL_GetTicks64();
-	u64 current_tick = gs->game_time_ms - last_sdl_tick;
-	double time_step = 0;
-
-	// NOTE: update sim time base on time since last frame * sim_speed
-	if (gs->running) {
-		u64 last_game_tick = gs->sim_time_ms;
-		gs->sim_time_ms = gs->sim_time_ms + current_tick * gs->sim_speed;
-		u32 diff_ms = gs->sim_time_ms - last_game_tick;
-		time_step = double(diff_ms) / 1000;
-	}
-
-	for (u32 i = 0; i < gs->num_orbits; i++) {
-		GameOrbit& orbit = gs->orbits[i];
+	double time_step = getTimeStep(gs);
 
-		if (orbit.in_use && orbit.satellite_entity) {
-			if (gs->running) {
-				updateSatelliteModel(orbit.system, time_step);
-				updateSatelliteEntity(orbit.satellite_entity, orbit.system.sat);
-				// TODO: update EllipseEntity per frame
-				//updateOrbit(gs->system, ellipse_entity);
-			}
-		}
-	}
+	for (u32 i = 0; i < gs->num_orbits; i++)
+		updateOrbit(&gs->orbits[i], gs->running, time_step);
 }
 
 void