Tungsten is a refractory metal used in aerospace applications. Melting point: 3,422 °C. Tensile strength: 1,510 MPa.
Tungsten is a metal with a superpower that matters enormously to rocket engineers: it has the highest melting point of any metal — in fact, the highest of any known element. That single trait lets it survive places inside a rocket where almost anything else would simply melt away.
Quick facts
- Chemical symbol: W (from its old name, “wolfram”); atomic number 74.
- Melting point: 3,422 °C (6,192 °F) — the highest of any metal and of any known element.
- Boiling point: about 5,930 °C (10,706 °F), also the highest of any metal.
- Density: 19.25 grams per cubic centimeter — about 1.7 times as dense as lead, and comparable to gold and uranium.
- Other records: the highest tensile strength (resistance to being pulled apart) of any pure metal in its elemental form.
- Common rocket alloy: W-25Re, meaning 25% rhenium mixed in by weight.
What it is and how it works
Tungsten is a “refractory” metal — a word that simply means it stays solid and strong at extremely high temperatures. Its best-known job in rocketry is lining the nozzle throat. A rocket nozzle is the bell-shaped exhaust at the back of an engine; the throat is its narrowest point. Burning gases at around 3,000 °C are funneled through that throat and squeezed up to the speed of sound, then fan out and accelerate further to push the rocket forward. Because the throat is the hottest, most tightly pinched spot in the whole engine, it takes the worst of the heat and the scouring blast.
Almost any ordinary material would melt or wear away under that blast. Tungsten’s record-high melting point lets a throat insert hold its exact shape under the heat and the scouring, high-speed exhaust. Keeping the throat geometry stable keeps the thrust stable.
There is a catch: pure tungsten is brittle and hard to machine at room temperature. So engineers mix it with other metals. Adding rhenium (as in the W-25Re alloy) makes it ductile — bendable and workable instead of glass-like. The recipe stays near 25% rhenium to avoid forming a brittle “sigma phase,” an unwanted internal structure that would weaken the metal. A different approach uses tungsten-copper composites with a clever trick: at extreme temperatures the copper vaporizes and carries heat away, cooling the surface from within — a process called transpiration cooling.
Tungsten’s enormous density does a second job in spacecraft. A small block weighs a lot, which makes it ideal as ballast — adjustable mass used to shift a vehicle’s center of gravity. The same density also stops radiation efficiently, so a compact tungsten block can shield sensitive electronics without taking up much room.
Why it matters
The nozzle throat is the single most heat-stressed and force-stressed part of a rocket engine. If the throat erodes, performance drops — or the engine fails catastrophically. Tungsten’s resistance to melting and erosion makes reliable, high-performance propulsion possible, especially for solid rocket motors and small thrusters that cannot use elaborate cooling systems.
Beyond engines, no other practical metal packs as much mass into as little volume. That gives designers a way to add precise weight for trajectory and attitude control, or to shield against radiation, while saving scarce space — a real advantage when every cubic centimeter and every degree of trim counts.
Where it is used
- Mars Science Laboratory (Curiosity rover): carried eight tungsten masses for balance — two 75 kg (165 lb) “cruise balance masses” jettisoned before entry, plus six 25 kg masses dropped during descent, to steer the spacecraft by shifting its center of mass.
- UGM-27 Polaris missile: the Polaris A-3 used silver-infiltrated tungsten in its rocket nozzle throats to withstand the exhaust heat.
- Solid rocket motors: tungsten-copper and W-25Re alloys are preferred throat-insert materials, prized for resisting erosion at extreme temperatures.
- Small thrusters: tungsten and tungsten-rhenium are flight-proven choices for the throat regions of compact engines that cannot carry elaborate cooling systems.
- Satellites and spacecraft: tungsten blocks as counterweights, ballast, and compact radiation shielding.
Because tungsten is so heavy, dense, and hard to machine — and because rhenium is rare and costly — designers reserve it for the few spots where nothing else survives.
W 99.95%+
| DENSITY | 19 kg/m³ |
| TENSILE STRENGTH | 1,510 MPa |
| YIELD STRENGTH | 750 MPa |
| STRENGTH-TO-WEIGHT | 78441.6 kN·m/kg |
| MELTING POINT | 3,422 °C |
| MAX SERVICE TEMPERATURE | 2,500 °C |
| THERMAL CONDUCTIVITY | 173 W/m·K |
| THERMAL EXPANSION | 4.5 µm/m·K |
| CATEGORY | Refractory Metal |
| DESIGNATIONS | ASTM B760, AMS 7725 |
| MANUFACTURER | Plansee / Global Tungsten & Powders |
| DENSITY | 19 kg/m³ |
| TENSILE STRENGTH | 1,510 MPa |
| YIELD STRENGTH | 750 MPa |
| MELTING POINT | 3,422 °C |
| MAX SERVICE TEMP | 2,500 °C |
| THERMAL CONDUCTIVITY | 173 W/m·K |
| THERMAL EXPANSION | 4.5 µm/m·K |
| CORROSION RESISTANCE | Good |
| WELDABILITY | Poor |
| MACHINABILITY | Very Poor |
| COST RATING | High |
