Define your spacecraft
Open Edit spacecraft to use the centered setup modal. Its first step covers mass and environment; Continue to propulsion opens system and operating-point inputs. Save spacecraft applies the draft. Cancel, close, or Escape discards it. The mass summary shows dry mass, propellant and total wet mass as you edit. Enter dry spacecraft mass (all hardware, no loaded propellant), actual loaded propellant, and the explicit unusable reserve. The initial 3% reserve represents 1% residuals plus 2% gauging; change it if your mission uses a different convention. No universal delta-v margin is added. Choose Custom chemical, Custom electric, or either supplied ThrustMe system. Enter the thrust and specific impulse you intend to assess. Electric propulsion also needs an orbit-distributed firing duty cycle. A 50% duty cycle doubles elapsed firing-related time, not the commanded delta-v. The public NPT30-I2-1U and JPT150-I2 datasheets supply bounds, not jointly attainable nominal operating points. Confirm your own thrust/Isp/power assumptions. The tool compares assumed operating power to available propulsion power and checks required total impulse against the supplier’s upper limit. A pass does not confirm performance or life at that point. JPT150 data is preliminary. Do not treat system wet mass as propellant load, or add it automatically to dry mass. Dry and propellant masses are not supplied separately in these datasheets. Only relevant extra fields appear: drag area/coefficient for atmospheric maintenance and LEO disposal; projected sun-facing area/reflectivity for GEO maintenance and graveyard clearance. The disposal calculation uses the same declared area: confirm this represents the intended end-of-life attitude.Spacecraft and orbit
The spacecraft and orbit fields define your mission, not an example-only demo. Initial values are editable assumptions. Set your actual mass, available propellant, propulsion operating point and starting orbit before relying on results.Examples
Start from an example offers optional, editable starting points. You can instead directly define your own mission. Loading an example after edits asks for confirmation; Keep my mission cancels replacement, and Undo plan action restores the previous mission after loading. All of this is in-memory only. Supplier examples are illustrative assumptions, not published paired operating points.Define the initial orbit
Use the Initial orbit controls at the left of the timeline. On mobile, tap Edit orbit above the chart to expand the inputs; closing the editor keeps your changes. Enter perigee and apogee altitudes, inclination, and UTC start epoch. Equal apsides define a circular orbit. GEO maintenance and relocation also require a declared reference GEO longitude. Orientation and initial anomaly are unconstrained. If your first maneuver needs a known wait to an apsis, node or operational opportunity, add a Coast phase. The tool does not solve a launch window.Compose the mission
Use Add mission phase or an insertion control on a phase boundary. Hover or focus a phase for a compact result preview; click or tap it to edit its inputs and inspect full results. Rename, duplicate, move and remove phases in the contextual editor. Drag intermediate phases to reorder them, or focus a phase and use Alt+Left/Right. The editor also has move buttons. Undo restores structural changes and example replacement. The phase library is searchable and keyboard accessible. Each phase consumes the previous estimated orbit, mass and epoch. Decommissioning is the fixed final leg. New phases are inserted before it; it cannot be moved, duplicated or removed. Collision avoidance is an automatic allowance, not a selectable leg.Inspect the timeline
The central plot uses mission elapsed time on its horizontal axis. Switch between the six orbital-element selectors below it. The existing estimator supplies phase-boundary values for semi-major axis, eccentricity and inclination. RAAN, argument of periapsis and true anomaly are labeled Not modeled in their selectors; select one to read the explanation. GEO longitude is a separate quantity. Dots are computed phase endpoints; dashed connections are schematic. They do not describe a propagated transfer path or motion within a coast. Hover the plot to inspect an endpoint, or focus it and use Left/Right. Enter opens the corresponding phase. Global budget totals remain below the workspace. The phase-order strip keeps every phase readable, even when its duration is too short to resolve at the current time scale. Use Select mission phase and Fit phase to inspect a short interval; Edit phase opens its inputs. Fit mission restores the entire time span. The selected phase stays highlighted in the phase strip and chart after its editor closes, with its name and computed interval above the plot. Switching orbital elements preserves the selected phase and time window. Decommissioning stays at mission end; its policy and full results are available through Edit disposal.Maneuver library
Browse Reach your orbit, Position & synchronize, and Operate & wait. Select an activity to see a schematic, then add it and configure its inputs. The altitude slider explores the schematic only; it does not change your mission. These are explanatory diagrams, not propagated trajectories. Chemical transfers show discrete burns; electric transfers show continuous-thrust concepts.
Circular-transfer, plane, phasing and operational models require circular endpoints. Circularize an elliptical injection orbit first. Drift altitude below nominal advances relative phase; above nominal delays it. The transfer arcs themselves accumulate phase, which is included when solving the remaining dwell. If those arcs overshoot your requested shift, move the drift orbit closer or change the requested shift.
An operational interval contains its maintenance. Do not add a second coast of the same duration. A standalone coast has no hidden maintenance and retains the nominal orbit; it does not estimate perturbation-driven decay.
Read the result
- Calculation: whether every defined phase produced an estimate. Invalid/unsupported phases block dependent endpoints; earlier subtotals remain.
- Mission accounting: whether phase inputs and mission scope have been reviewed. Estimates account for defined phases only, not proof of a complete mission. The interface has no separate mission-coverage checklist; scope limitations remain visible in the results.
- Estimated limits: propellant/reserve, selected supplier impulse/power, and firing availability checks. This is not overall mission feasibility.