Sierra Space tests upcoming in-space habitat as other commercial space stations continue development

by John Sharp
Burst test

On Jan. 21, Sierra Space performed an “ultimate burst pressure test” on a full-scale model of its Large Integrated Flexible Environment (LIFE) habitat — an inflatable space station module. The launcher-agnostic habitat is designed to be launched encapsulated within any four-meter fairing, docked to a space station in orbit, and then inflated to a 9-meter by 16-meter structure, ready for operation.

Alongside Sierra Space, other private commercial space station companies and agencies are continuing to develop their space stations and deliver the first segments of their upcoming stations. Several of these companies have received contracts from agencies like NASA, while others are fully private with no assistance from NASA or other agencies.

Sierra Space continues to test upcoming in-space habitat

Sierra Space’s burst test specifically focused on the LIFE habitat’s pressure shell – otherwise known as the restraint layer – which comprises Vectran straps along with a series of other high-strength fabric materials. Sierra Space, working with its exclusive softgoods technology partner ILC Dover, has specifically designed and tested Vectran straps at the component and sub-scale levels before this full-scale test. ILC Dover has a rich space heritage having previously manufactured the Apollo astronauts’ space suits. NSF recently spoke with Sierra Space about the test and the materials used to learn more about LIFE and how its development is progressing.

The test was conducted at NASA’s Marshall Space Flight Center in Huntsville, Alabama. The pressure shell for Sierra Space’s LIFE habitat consists of expandable “softgoods,” or woven fabrics that perform like a rigid structure once inflated. During an ultimate burst pressure test, the teams inflate the test article until it fails, which helps determine how strong its softgoods materials would be under extreme stresses in the harsh environment of space. The full-scale unit in this test reached 77 pounds per square inch (psi) before it burst, which well exceeds (by more than 27 percent) NASA’s recommended level of 60.8 psi (maximum operating pressure of 15.2 psi multiplied by a safety factor of four).

The LIFE Habitat passed the pressure test by more than the required safety margin, and Sierra Space will repeat the test to prove that there is consistency in the design and manufacturing standards. The company said that the designed operating pressure is “15.2 psi for all sizes of modules” and that “the number of LIFE full and sub-scale test articles are based on Sierra Space’s Softgoods Certification process. Currently, we are planning several tests in 2024 on both the Sub and Full Scale. The next LIFE full-scale ultimate burst pressure test is planned for June 2024 or sooner. The primary architecture and geometry of the LIFE full-scale article is stable but Sierra Space and its partners are always looking to improve our processes in regards to repeatability, quality, and performance.”

In response to a question as to how the interior would be fitted into an inflatable module, Sierra answered, “LIFE does not require an additional shell once deployed in space. Its Softgoods Layers provide all that is required for the habitat to operate in space safely and reliably. The Softgoods structural layers in the launched configuration are packed around a metallic core that provides the volume and connections for the habitat’s operational systems along with the storage of many support systems. Once the habitat is in operation, pressurized, and at full volume, additional missions will complete the interior layouts and expand its capabilities.” 

Regarding the exterior shell, NSF asked Sierra how the modules are protected against impacts from orbital debris, and what would be the consequences of penetration of the structure, to which they responded, “LIFE’s Softgoods Layers encompass the following: Air Barrier Layer, Restraint Layer, Micrometeoroid Orbital Debris (MMOD) Layer and Multi-layer Insulation Blanket. The MMOD layer is specifically designed to stop or mitigate the operational environment’s orbital debris. We design the MMOD layer to protect the space habitat from the orbital debris with a series of stack material layers that will be tested via Hypervelocity Impact testing prior to being integrated onto the habitat. As far as a possible penetration in the overall Softgoods structure, if such a rare event should occur, Sierra Space has mitigation plans in place, and they are currently in the testing and evaluation phase.”

When asked whether LIFE habitat modules will be available to operators other than Blue Origin, the company responded, “LIFE will be available to potential customers or operators within the scope of Sierra Space’s development pipeline.” Finally, when asked if LIFE could be used by 2029, the company said, “Yes, LIFE habitats are planned to be in operation by the end of the decade.”

NASA’s Commercial Low Earth Orbit Development Program

Sierra Space’s LIFE habitat pressure test is part of the wave of progress heralding a new era of commercial space station development. Three different projects are under the auspices of NASA’s Commercial Low Earth Orbit Development Program (CLD).

In 2020, NASA selected Axiom Space to provide a habitable commercial module to attach to the ISS. In December 2021, NASA awarded Space Act Agreements to Blue Origin, Nanoracks, and Northrop Grumman to develop free-flying destinations. Both efforts were to help mature commercial designs and lay the groundwork for NASA to be one of many customers purchasing services in low-Earth orbit.

Since the original tranche of four CLD agreements was made, one of the companies, Northrop Grumman, has abandoned its original plans, instead joining the Starlab development partnership with Voyager Space, Airbus, and NanoRacks. The funds that had been intended for Northrop Grumman were reassigned early in 2024 between Blue Origin ($42 million) and Starlab ($57.5 million), bringing their total funding to $172 million and $217.5 million, respectively.

At the end of December 2023, NASA reported that all three of the partner projects had achieved their significant milestones for the year, and were all on course to meet the requirements of their contracts.

Orbital Reef | Blue Origin and Sierra Space

Sierra Space LIFE habitat modules form part of the Orbital Reef commercial space station, which is being developed in a partnership between Sierra Space and Blue Origin. Orbital Reef is partly funded by a Space Act Agreement administered by NASA. 

Orbital Reef

Orbital Reef with LIFE habitats. (Credit: Orbital Reef)

The project aims to build “a multi-purpose business park, 250 miles above Earth.” Renders show multiple LIFE habitat modules attached to a large central structure forming a backbone for the station. Sierra Space has been testing its inflatable modules incorporating metal placeholders for integrating windows, airlocks, robotic arms, and other features, into the softgoods layer. 

Blue Origin has built and tested prototype windows for use on Orbital Reef. The windows are larger than current space station windows, approximately twice the size of a car windshield, and will provide stunning views from the station.

Blue has constructed a building, known as the Reef Pathfinder Building, in its Exploration Park manufacturing center, located near Launch Complex 36 at the Cape Canaveral Space Force Station.

Having received its initial funding from a NASA Space Act Agreement under CLD Phase 1, Blue Origin has recently been posting on social media about the way recent deliverables will shape the CLD Phase 2 contract awards, due in 2026. 

Starlab | Voyager Space Airbus

Starlab LLC was formalized on Jan. 9, 2024 as a joint venture between Voyager Space and Airbus. It includes Nanoracks, which Voyager Space acquired in May 2021. The Chief Executive Officer is Tim Kopra, a former NASA astronaut who has completed two missions to the International Space Station (ISS).


Starlab render. (Credit: Starlab)

Voyager Space has previously announced two practical projects being developed under its Space Act Agreement: an alternative urine processor (AUP) and a free-space optical (FSO) link. The AUP will be tested under realistic operating conditions at NASA’s Marshall Space Flight Center in Huntsville, Alabama.

The FSO will be attached to the Bishop Airlock, an existing integral part of the ISS, and will test a high-bandwidth optical communications link between a ground terminal and the flight terminal on the ISS. 

Both demonstrations are seen as vital component testing and integral to the development of Starlab.

Starlab signed a launch deal with SpaceX at the end of January. The two parties intend to launch the entire fully assembled Starlab on board a Starship. At approximately eight meters in diameter, Starlab will take full advantage of Starship’s cavernous payload space. The launch is currently expected to take place no earlier than 2028.

Starlab LLC recently recruited former NASA Administrator Jim Bridenstine as chair of its advisory board.

In February, Voyager Space flew three payloads to the ISS onboard the CRS NG-20 Cygnus vessel. One of the payloads is the GITAI 2-meter class Modular Robotic Arm which will be attached to the Bishop Airlock. The S2 will conduct an external demonstration of in-space servicing, assembly, and manufacturing while onboard the ISS. 

Axiom Station | Axiom Space

In contrast to Orbital Reef and Starlab, which are funded under NASA Space Act Agreements, Axiom Station is being built under a fixed-price contract between NASA and Axiom Space. Already flying private commercial crews to the ISS in SpaceX Crew Dragon spacecraft, Axiom will attach at least two of its four planned Axiom Station modules to the ISS. These will operate integrally with the ISS until 2030 when it is due to be decommissioned. At this time, the Axiom Station will detach and operate independently.

The NASA Multi-Purpose Logistics Module MPLM-2 (Raffaello), built by Thales Alenia, Turin, Italy, will be repurposed by Axiom as the Research and Manufacturing Facility for deployment to Axiom Station. The MPLM-2 module was relocated by NASA to Axiom’s Houston premises in April 2023.

MPLM-2 was flown on four Shuttle missions as a transferable module for the ISS. A similar module, MPLM-1 (Leonardo), was repurposed as the Permanent Multipurpose Module logistics module, now permanently attached to the ISS. 

The first of the new modules, Axiom Hab One, is under construction at Thales Alenia. The bulkheads were recently welded and are being readied for testing. Hatches are also built and ready for testing. The company expects the module to be shipped to Axiom in Houston shortly for integration and completion.

It is not yet known which vehicle will launch the modules into orbit to the ISS.

Haven-1 | VAST Space

A non-NASA private commercial space station enterprise is VAST Space of Long Beach, California, which has already earmarked a SpaceX Falcon 9 to launch its single-module station as early as August 2025. If met, this target would make Haven-1 the first-ever commercial space station in orbit. 

In the meantime, the company has stated an intention to bid to provide private crew services to the ISS, in much the same manner as, and in competition with, Axiom Space. Axiom currently has one flight remaining under contract with NASA and has not so far had to compete for the flights on SpaceX Crew Dragon since they commenced private flights in 2022.

Haven-1 will support a crew of four for a 30-day stay, but despite the imminent launch date, no flight hardware has been revealed to the public so far.

VAST has several notable personnel on its books, including Dr. Garrett Reisman and Dr. Andrew Feustel, both from NASA, Peter Russell-Clarke, previously with Apple, and Jim Martz from SpaceX.

Starmax | Gravitics

Another non-NASA private commercial space station enterprise is Gravitics of Marysville, Washington, which is designing and building a range of standard space station modules known as Starmax. With up to 400 cubic meters in volume, the prototype module is 7.6 meters in diameter and 9.7 meters in length. The company has successfully tested its pressure domes, reaching and maintaining 26.6 psi, almost twice the standard operating pressure of the ISS, which is 14.7 psi.

They have also tested Reaction Control Thrusters, rated at 445 Newtons, the gaseous methane/oxygen thrusters have been fired 238 times in 24 hours on the ground-based test rig.

Gravitics is preparing to send experimental components to the ISS as part of the development and verification of systems starting with several Smart Tanks for Space, which are specifically designed to measure fuel levels using Electrical Capacitance Tomography smart gauging. This is timely, as the issue of determining fuel levels will be critical, as on-orbit refueling becomes a necessity for both Artemis and many future missions beyond Earth orbit.

(Lead image: Sierra Space’s ultimate burst pressure test reaches the limit. Credit: Sierra Space)

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