I think that should be it for the fuel handling

mission.go

@@ -2,6 +2,7 @@ package smd
 
 import (
 	"fmt"
+	"log"
 	"math"
 	"sync"
 	"time"
@@ -113,8 +114,9 @@ func (a *Mission) Propagate() {
 	}
 	a.Vehicle.logger.Log("level", "notice", "subsys", "astro", "status", "finished", "duration", durStr, "Δv(km/s)", math.Abs(vFinal-vInit), "fuel(kg)", initFuel-a.Vehicle.FuelMass)
 	a.LogStatus()
-	if a.Vehicle.FuelMass < 0 {
+	if a.Vehicle.handleFuel && a.Vehicle.FuelMass < 0 {
 		a.Vehicle.logger.Log("level", "critical", "subsys", "prop", "fuel(kg)", a.Vehicle.FuelMass)
+		log.Fatal("cannot continue without fuel")
 	}
 	wg.Wait() // Don't return until we're done writing all the files.
 }

spacecraft.go

@@ -23,6 +23,7 @@ type Spacecraft struct {
 	logger      kitlog.Logger
 	prevCL      *ControlLaw // Stores the previous control law to follow what is going on.
 	Drag        float64
+	handleFuel  bool
 }
 
 // SCLogInit initializes the logger.
@@ -181,12 +182,12 @@ func (sc *Spacecraft) ToXCentric(body CelestialObject, dt time.Time, o *Orbit) f
 
 // NewEmptySC returns a spacecraft with no cargo and no EPThrusters.
 func NewEmptySC(name string, mass uint) *Spacecraft {
-	return &Spacecraft{name, float64(mass), 0, NewUnlimitedEPS(), []EPThruster{}, false, []*Cargo{}, []Waypoint{}, []func(){}, SCLogInit(name), nil, 0}
+	return &Spacecraft{name, float64(mass), 0, NewUnlimitedEPS(), []EPThruster{}, false, []*Cargo{}, []Waypoint{}, []func(){}, SCLogInit(name), nil, 0, false}
 }
 
 // NewSpacecraft returns a spacecraft with initialized function queue and logger.
 func NewSpacecraft(name string, dryMass, fuelMass float64, eps EPS, prop []EPThruster, impulse bool, payload []*Cargo, wp []Waypoint) *Spacecraft {
-	return &Spacecraft{name, dryMass, fuelMass, eps, prop, impulse, payload, wp, make([]func(), 5), SCLogInit(name), nil, 0}
+	return &Spacecraft{name, dryMass, fuelMass, eps, prop, impulse, payload, wp, make([]func(), 5), SCLogInit(name), nil, 0, fuelMass > 0}
 }
 
 // Cargo defines a piece of cargo with arrival date and destination orbit