VS-43: test the events between propulsion stages

AEB’s VS-43 account describes a proposed controlled suborbital vehicle drawing on the upper-stage heritage of VLS-1. Its intended role included testing navigation — open definition, guidance — open definition, control and events associated with deploying a satellite. The design was presented as a bridge between earlier research vehicles and the more complex orbital launcher. This lesson treats that account as a development proposal, not as a record of a completed VS-43 flight.

The distinction matters because a rocket is more than a stack of motors. During a mission, systems must determine the vehicle’s state, decide how to respond and carry out the required actions. Navigation estimates where the vehicle is and how it is moving. Guidance determines the desired path or commands. Control — open definition acts to bring motion toward those commands. The functions work together while retaining different responsibilities.

The proposed tests included events such as fairing — open definition separation, orientation changes, spin-up and payload separation. A fairing protects a payload during part of ascent; releasing it at the appropriate time is different from producing thrust. Likewise, rotating an assembly before a later event is a change in its state that needs to occur under the intended conditions. A motor-only demonstration cannot establish every part of this sequence.

Imagine a fictional test in which a command is issued but a separation sensor does not confirm the expected event. The team needs to distinguish the command, the physical action and the reported status. Their timestamps and supporting measurements can help determine whether the event failed, the sensor failed or the reporting path lost information. The example illustrates an evidence problem, not a claimed VS-43 anomaly.

Separate the sequence’s evidence

A suborbital test can examine selected orbital-launch functions while remaining a suborbital mission. Its usefulness depends on how well the tested conditions represent the intended application. A release demonstrated with one mass, orientation and environment may need further work for another configuration. Test planning should specify the question, relevant conditions, measurement accuracy and criteria for deciding whether the objective was met.

AEB’s design account also described using existing VLS infrastructure and experience. Reuse can reduce the effort required to prepare a test, but inherited equipment needs an assessment for its new role. The related VS-50 proposal emphasizes different technology questions, so the two should not be merged merely because both names begin with VS. Study the uncertainty each proposed flight was intended to reduce before comparing their contribution to a larger launcher program.