A boilerplate spacecraft, also known as a mass simulator, is a nonfunctional craft or payload that is used to test various configurations and basic size, load, and handling characteristics of rocket launch vehicles. It is far less expensive to build multiple, full-scale, non-functional boilerplate spacecraft than it is to develop the full system (design, test, redesign, and launch). In this way, boilerplate spacecraft allow components and aspects of cutting-edge aerospace projects to be tested while detailed contracts for the final project are being negotiated. These tests may be used to develop procedures for mating a spacecraft to its launch vehicle, emergency access and egress, maintenance support activities, and various transportation processes.
Boilerplate spacecraft are most commonly used to test crewed spacecraft; for example, in the early 1960s, NASA performed many tests using boilerplate Apollo spacecraft atop Saturn I rockets, and Mercury spacecraft atop Atlas rockets (for example Big Joe 1). The engine-less Space Shuttle Enterprise was used as a boilerplate to test launch stack assembly and transport to the launch pad. The development of NASA's Project Constellation used boilerplate Orion spacecraft atop an Ares I rocket for initial testing. More recently, on February 6, 2018, SpaceX founder Elon Musk's Tesla Roadster was used as a dummy payload on the maiden launch of the company's Falcon Heavy rocket.