Iss Burn Rate Calculation

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ISS Propellant Burn Rate Calculator

Mission Analysis Results

function calculateISSBurn() { var initial = parseFloat(document.getElementById('initialPropellant').value); var current = parseFloat(document.getElementById('finalPropellant').value); var days = parseFloat(document.getElementById('observationDays').value); var resultDiv = document.getElementById('issResult'); if (isNaN(initial) || isNaN(current) || isNaN(days) || days initial) { alert("Current propellant cannot be greater than initial propellant (unless a refueling mission occurred)."); return; } var totalConsumed = initial – current; var burnRate = totalConsumed / days; var remainingLife = burnRate > 0 ? (current / burnRate) : 0; document.getElementById('totalUsedText').innerHTML = "Total Propellant Consumed: " + totalConsumed.toFixed(2) + " kg"; document.getElementById('dailyRateText').innerHTML = "Average Daily Burn Rate: " + burnRate.toFixed(3) + " kg/day"; if (burnRate > 0) { document.getElementById('remainingDaysText').innerHTML = "Estimated Propellant Depletion in: " + remainingLife.toFixed(1) + " days"; } else { document.getElementById('remainingDaysText').innerHTML = "No net consumption detected during this period."; } resultDiv.style.display = 'block'; }

Understanding ISS Propellant Burn Rate

The International Space Station (ISS) maintains a Low Earth Orbit (LEO) at an average altitude of approximately 400 kilometers (250 miles). Despite being in space, the ISS experiences a small amount of atmospheric drag from the Earth's thermosphere. This drag causes the station to lose altitude over time, a process known as orbital decay.

Why Does the ISS Use Propellant?

To prevent the ISS from re-entering the Earth's atmosphere, it must periodically perform "re-boost" maneuvers. These maneuvers use propellant (primarily unsymmetrical dimethylhydrazine and nitrogen tetroxide) stored in the Progress resupply vehicles or the Zvezda service module thrusters. The burn rate is influenced by:

  • Solar Activity: During high solar activity, the Earth's atmosphere expands, increasing drag and requiring more frequent re-boosts.
  • Station Orientation: The "attitude" of the station affects its cross-sectional area and drag coefficient.
  • Debris Avoidance: Sudden maneuvers to avoid space debris consume extra propellant outside of normal maintenance.

How to Calculate the Burn Rate

Calculating the burn rate is essential for mission logistics and scheduling resupply missions. The basic formula used by this calculator is:

Daily Burn Rate = (Propellant at Start – Propellant at End) / Days Elapsed

Example Calculation

Imagine the ISS starts a 30-day monitoring period with 4,000 kg of propellant. After 30 days of standard operations and one scheduled re-boost, the remaining propellant is 3,850 kg.

  1. Total Consumed: 4,000 kg – 3,850 kg = 150 kg
  2. Daily Burn Rate: 150 kg / 30 days = 5 kg/day
  3. Projected Depletion: 3,850 kg / 5 kg/day = 770 days of remaining fuel

Operational Significance

Ground controllers at NASA (Houston) and Roscosmos (Moscow) monitor these rates meticulously. If the burn rate exceeds predicted models, it may indicate a leak or unexpected atmospheric expansion due to a solar flare. Accurate burn rate calculation ensures that the station remains habitable and safe for the crew on board.

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