1. The elevator that could not be launched

Arthur C. Clarke’s The Fountains of Paradise returns as the recalled work because its space elevator is the ultimate example of in-space assembly: a structure that can only exist if pieces launched separately are connected in orbit. The desktop is far smaller, but it shares the problem. If segments or attachments are to be added after launch, they need a common interface language.

This entry reads about the basics of ISAM interfaces and standards.

2. What ISAM covers

In-space servicing, assembly, and manufacturing (ISAM) is a suite of capabilities used on orbit, on celestial surfaces, and in transit. The White House ISAM National Strategy defines the field and outlines six strategic goals, including advancing ISAM research and development, expanding scalable infrastructure, accelerating the commercial industry, and promoting international collaboration.

COSMIC, the Consortium for Space Mobility and ISAM Capabilities, was created by NASA to coordinate government, industry, and academia around these goals. NASA’s press release describes ISAM as encompassing spacecraft repair, refueling, relocation, retrofitting, 3D printing, and orbital assembly.

3. Why standards matter

ISAM only becomes routine when interfaces are predictable. A servicer must know what to grab, how to connect, and what services to expect. A client must know what features to provide so that future servicers can work with it. Without standards, every servicing mission is a bespoke engineering project.

The early NASA Space Assembly and Servicing Working Group recognized this and created Interface Standards Committees for mechanical, electrical, fluid, thermal, and optical interfaces. A 1994 NTRS summary notes that the goal was a “Standard Set” of interface hardware standards for satellites and platforms, including navigation aids, grasping/berthing/docking interfaces, and utility connectors.

4. The main interface domains

ISAM interfaces span several domains:

  • Mechanical: docking rings, berthing posts, grapple fixtures, alignment features, and tool drives.
  • Electrical: power transfer and data buses across the interface.
  • Fluid: propellant, coolant, or gas transfer couplers.
  • Thermal: heat paths across the joint.
  • Information: command and telemetry protocols, safety handshakes, and identification.

A spacecraft that wants to be serviced must provide features in each relevant domain. A spacecraft that wants to service others must be able to connect to those features.

5. What this changes

  • ISAM is not a single technology but a family of capabilities supported by standards.
  • The desktop’s attachment grid and segment interfaces should be evaluated against emerging ISAM standards.
  • The next entry will read about specific docking and robotic servicing standards.