Tungsten and r-7 rocket: what they have in common

1. Step 1. Tungsten — is material for — Ion thruster. The cathodes are tungsten.
2. Step 2. Ion thruster — is part of — Space probe. Ion thrusters (Dawn).
3. Step 3. Space probe — uses — Multistage rocket. Launch.
4. Step 4. Multistage rocket — includes — R-7 rocket. A clustered multistage layout.

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