How much of the world's xenon has been used in spaceflight altogether? Is it a lot? Did it cost a lot?
Why was SERT-1 put in a suborbital trajectory (4000 km apogee) while SERT-2 (1970-009A) was put in a 1000 km circular polar orbit?
Mass ratio of solar-electric versus radioisotope thermo-electric power for propulsion; beyond how many AU do RTGs win?
What is Australia's Bartolomeo platform? When does it arrive at the ISS; when and where will it be attached?
What's this small source of glowing blue plasma next to Psyche's Hall effect thruster for? What does it do and why does the plasma curve and connect?
What is the most energy efficient & inexpensive propulsion system other than chemical fuel oxidizer that could be used in rockets?
How to calculate the kilowatt hours (kW-h) needed for a solar-electric engine to produce a given delta-v?
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