Made In Space Interferometer
In-space manufacturing promises to be a key driver for developing space resource technologies. Building and assembling large structures in space allows the use of efficient designs that don’t require robust structures for the one time g-force requirements of launch. Made In Space has recently proposed a long-baseline interferometer that uses in-space manufacturing techniques for assembling opposing booms up to 50 m (164 ft) in length from a 24U small-sat chassis.
Interferometry is the technique of combining multiple electromagnetic waves together. For astronomy, interferometry is often used to combine visible light beams from multiple telescopes (like at the the ESO VLT) or radio waves from large arrays (very-long-baseline interferometry used at the VLA or ALMA). Interferometry is used in astronomy to achieve high resolution observations using relatively small telescopes rather than a single monolithic telescope.
Space telescopes bypass the atmospheric limitations of ground based telescopes, while also enabling long integration times. Space based interferometry is a revolutionary technology for astronomy because it changes the paradigm of using a single large billion dollar telescope (like Hubble or JWST). Instead, multiple smaller million dollar telescopes can have their signals combined to create a gigantic synthetic aperture with much higher resolution than the single telescopes. Made In Space’s proposed interferometer is an early step in developing an affordable space interferometer with current technology.
The Made In Space designed system is called the Optimast-SCI (Structurally Connected Interferometer). It is developed as part of the Archinaut platform that enables autonomous manufacturing and assembly of spacecraft systems in orbit. Archinaut was originally developed as a NASA Tipping Point Technology in 2015, with in-orbit boom assembly being an initial use case.
The central component of Archinaut is the internal 3D printer called the Extended Structure Additive Manufacturing Machine (ESAMM). Made In Space successfully tested the ESAMM design within a thermal vacuum chamber at NASA Ames Research Campus in 2017. Multiple truss structures up to a meter in length were manufactured within the vacuum chamber. This test represents the first time an object has been 3D printed within space-like conditions.
The ESAMM would be used within the central Optimast-SCI satellite to assemble the boom structures. The design allows for booms between 10 and 50 m (32 and 152 ft) long. One side of each boom supports a mirror assembly that contains a fine position adjustment mechanism. These assemblies collect signals and redirect them through the center of boom towards the central satellite body. Each light path is proposed at being about 2.54 cm² (1 in²) wide.
In addition to housing the boom building ESAMM, the central satellite also houses the internal optics bench. The optics hardware ensures the electromagnetic waves from each boom are superimposed (line up and combine peak to peak, trough to trough), which requires nanometer precision. The CCD or similar recording instrument will receive the beam thereafter, recording the observation for transmission back to Earth.
A novel ability of the Optimast-SCI is that the two booms can be adjusted on-the-fly, allowing the interferometer baseline to change without complicated mechanisms. This is handled by offsetting each boom from each other, and having each boom mounted on roller gantries that allow extension and retraction movements. This is a unique ability that should allow the system to observe a wide range of targets.
Large telescope assemblies are a prime use case of in-space manufacturing because large structures can be built without having to develop complicated support and deployment structures. Additionally, the manufacturing techniques are scalable, autonomous, and self contained. The possibilities of structures that could be assembled and manufactured in space is near limitless. Supplying the material feed-stocks to these manufacturing systems will be a strong driver for developing cheaper launch options and asteroid based resource processing techniques.