Total

Power Propellant

1128 24 kW H,D,He

Figure 7.36. Schematic view of the system for a VASIMR flight experiment [NASA-JSC, 2000].

pressure on magnetic confinement of plasma. To ensure full plasma control by the magnetic fields in the second and third section of the VASIMR, plasma must be reasonably collisionless. This implies the plasma density should be low, a requirement opposite to that of keeping radiative losses under control and of achieving high power density (power/unit cross-section of the engine, or power/volume). It is practically certain that a VASIMR will be much larger compared to other types of electric thrusters, i.e., its thrust per unit exit area will be lower.

The VASIMR concept is envisioned as eventually evolving into a real space engine of power up to the 100 MW mentioned. In 2000, NASA efforts were focusing on a flight opportunity for a radiation and technology demonstration mission sponsored by JSC, GSFC, and GRC teams. The first flight experiment planned using this new technology was designed around a 10-kW solar-powered spacecraft. The spacecraft with a VASIMR engine was to be lofted to several thousands of kilometers above Earth, and perform scientific measurements of the Van Allen radiation belts. A schematic view of this system and its tentative mass budget is in Figure 7.36.

After Project Prometheus and JIMO begun to be discussed, the future of VASIMR became less clear: VASIMR suits a manned mission better than the slower robotic missions planned by NASA in the near or middle term. However, development by NASA at the JSC is continuing. Figure 7.37 shows an older VASIMR technology development roadmap to full implementation in 2004. Linked arrows show ground-testing always leading flight experiments and space deployment at each incremental power level.

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