Table 1 Characteristics of basic design concept of thrust balances as shown in Fig. 2
From: Thrust measurement and thrust balance development at DLR’s electric propulsion test facility
Design type | Advantages | Disadvantages | Fig. 2 |
|---|---|---|---|
vertical weigh cell | • commercial systems are available • simple design | • cell has to carry all weight of thruster assembly • thrust has to be measured against thruster weight | (a) |
single arm pendulum | • simple design • high sensitivity | • thruster weight impacts measurement • thrust vector changes in operation w/o displacement compensation • pendulum length is crucial • oscillations may appear | (b) |
torsional pendulum | • very sensitive • low forces measurable • thruster weight has theoretically no impact on measurement | • needs to be well balanced • position of thruster must be accurately known • thrust vector changes in operation w/o displacement compensation | (c) |
inverted pendulum | • simple design • thruster weight has theoretically no impact on measurement | • active control required • position of thruster must be accurately known | (d) |
inverted double pendulum | • thruster weight has theoretically no impact on measurement • high sensitivity • thruster platform stays horizontal • free positioning of thruster | • active control required • complex mechanical design | (e) |
counterbalanced inverted pendulum | • thruster platform stays horizontal • free positioning of thruster • by trimming the weight, this system can be very sensitive • thruster weight has theoretically no impact on measurement • inherently stable with counterweights • sensitivity can be tuned | • may need active control • high sensitivity • very complex, many pivoting points | (f) |