Sierra Space wants to send an inflatable habitat with more volume than the entire International Space Station into space on a single 7m fairing launch. At least that’s the goal as the company begins working toward an actual test article even larger than the ones we’ve seen in recent testing.
They believe the ability to launch a relatively small uninflated habitat and then inflate it on orbit into a massive structure is the future of space stations in LEO and even beyond. With the recent completion of a second Ultimate Burst Pressure test, the company is making some significant progress. Here I will go more in-depth into their recent progress, even larger inflatable, upcoming testing, and more.
Even More Testing
Back in December of last year, we saw the first full-scale Ultimate Burst Pressure test (UBP) on the company’s 300 cubic-meter inflatable. These tests simply continue to fill the habitat with pressure until it explodes, recording the maximum pressure among other data.
In terms of what deems a successful pressure test, NASA’s recommended maximum operating pressure that an inflatable should withstand is 60.8 PSI. Which is also just 15.2 psi multiplied by a safety factor of four. On that first test, the inflatable burst at 77 PSI, exceeding NASA’s requirements by around 27%.
This leads us to just over a month ago when Sierra Space attempted another similar UBP test. The main difference here was alterations to the blanking plate, or large metal plate integrated with the softgoods materials. In the future that plate could instead be a window for example but presents challenges related to the overall strength of the inflatable.
Fortunately, on this test, they again were able to pass the agency’s requirements this time bursting at a pressure of 74 PSI, exceeding the requirements by 22%. The actual test articles are massive standing around 6m in length with a 9m diameter. The steel blanking plates measuring 4-ft x 4-ft (1.2m x 1.2m) were integrated into the highest loaded cylinder section of the article; both were 50 lbs. lighter than the ones used in the first full-scale test and accommodating larger windows.
Following the test the company said in a statement, “These back-to-back test results accelerate Sierra Space’s path to flight certification, verifying scalability for 10 cubic-meter and up to 1,400 cubic-meter structures based on the company’s current softgoods inflatable architecture.” They then mentioned, “Sierra Space is currently gearing up for a first test of its 500 cubic-meter space station technology next year.” This statement is significant as it means Sierra Space plans to continue testing even larger inflatables before in-space tests.
In addition, after the test, the Senior Principal Mechanical Engineer at Sierra Space was quoted saying, “This test and the prior two tests are the highest loaded inflatable tests ever. We’re verifying the ability to build a 27-foot diameter module and that’s not only applicable to LIFE 285, but that’s also applicable to LIFE 500.” He then said, “What that means is we’ve shown the ability to build a larger module than 27 feet, and that’s what’s utilized in a LIFE 1400, which is 150% the habitable volume of the International Space Station, in a single 7m fairing launch.”
Based on these comments it’s clear the company has some ambitious goals and is confident they can replicate some of the current test results with much larger inflatables. Assuming the next testing with the large 500 cubic meter volume habitat goes well, one of the next test articles could very well be LIFE 1400.
If all that wasn’t enough, on Sierra Space’s website they showcase a third LIFE variant with an internal volume of 5000 cubic meters. This would require a 9m fairing for launch and once inflated would feature a 22m length and 19m diameter. A single inflatable with more than 5 times the volume of the International Space Station.
The company has also made it clear that speed is important to them. Shawn Buckley, VP of Space Stations at Sierra Space said after the test, “No other company is moving at the speed of Sierra Space to develop actual hardware, stress-tested at full scale, and demonstrate repeatability. We’ve taken a softgoods system that very few companies around the world have been able to design, and now we have consistent, back-to-back results. A second successful full-scale test is an absolute game changer. We now know it’s possible to equal or surpass the total habitable volume of the entire International Space Station, in a single launch” he said.
Unique Materials
One challenge of creating a space habitat that’s inflatable is ensuring it can withstand the harsh space environment and things like orbital debris. The way Sierra Space has approached this has been with a bunch of individual layers.
You first have the restraint layer for LIFE, constructed of high-strength “softgoods” materials, which are sewn and woven fabrics – primarily Vectran – that become rigid structures when pressurized. They point out that under normal operating pressure, the Vectran softgoods materials become 5x stronger than steel, exceeding station lifetime performance safety factors. The restraint layer is complemented by a bladder allowing controlled inflation and pressurization to ultimate burst pressure test failure. Together this creates a structure strong enough to withstand micrometeoroid impacts and other projectiles.
It’s also protected by an MMOD multi-layer soft-goods shield that guards the habitat against space debris such as micrometeoroids. These layers of fabric, plus the internal outfitting, are meant to create ample safeguards against radiation.
For both of the pressure tests, due to their nature, they mainly focused on the LIFE habitat pressure shell – otherwise known as the restraint layer. The company highlights that they’ve been working with their exclusive softgoods technology partner ILC Dover, who has specifically designed and tested Vectran straps at the component and sub-scale levels prior to this full-scale test. So far these materials have yielded good results but there’s still quite a bit of work ahead of them.
One of the set-in-stone applications of this hardware is on the Orbital Reef Space Station. The most recent test actually “closed out Milestone #8 for Orbital Reef with Blue Origin under NASA’s Commercial Low Earth Orbit Development Program.” On that station, these inflatable modules along with the rigid modules provided by Blue Origin will create a commercial station in low Earth orbit.
In theory, New Glenn which has a 7m payload fairing and heavy-lift capabilities, would launch LIFE modules into orbit. It could even send the larger LIFE 1400 variant as well which would provide massive increases to Orbital Reef’s volume.
All that being said, even with the current progress, Orbital Reef isn’t expected to begin launching any segments until later this decade. This aligns with the fact that Sierra Space and the LIFE models still need a lot of testing including in space tests.
In regard to general progress the Sierra Space CEO said, “We are 100 percent committed to maintaining U.S. leadership in Low Earth Orbit. Sierra Space is leading the way with the first commercial space station to replace the International Space Station when it is decommissioned and ensure there is no gap in LEO. “Our revolutionary, expandable space station technology reinvents the space station. Our technology, for the first time, will enable the right unit economics that will usher in the full commercialization of space. Our biotech and industrial partners will utilize our factories of the future to innovate new products that will massively disrupt terrestrial markets and benefit life on Earth” he said.
On the standard size LIFE habitat, its meant to comfortably sleep four astronauts, with additional room for science experiments, exercise equipment, a medical center and even a garden, according to the company. In the past, Sierra Space was awarded a Space Act Agreement (SAA) by NASA, under the second Collaborations for Commercial Space Capabilities (CCSC-2) initiative.
This award by NASA provides support to a “pathfinder” space station, which serves as a technology demonstration for key elements of commercial space stations. This follows the theme of NASA pursuing other options in LEO as we get closer to the ISS’s retirement.
Sierra Space believes that one of the most remarkable features of the LIFE habitat is its adaptability to accommodate a range of businesses, from in-space semiconductor manufacturing to pharmaceutical microgravity research. The habitat leverages the unique conditions of zero gravity, offering an optimal environment for experiments and processes that benefit from this distinct microgravity setting, they say. With substantial volume, power, and data capabilities, they are confident that the habitat is primed for extended human habitation, both for low-Earth Orbit (LEO) missions and for the demanding challenges of long-duration voyages, such as Lunar and Mars surface habitation.
So far, the company has made some impressive progress and is getting closer to actually launching one into space. Over the next few months, we can expect the occasional update as they make progress toward their next test article and general development. Not too long from now we can expect to see LIFE 500 which is nearly twice the size of the test articles we just saw burst. If successful, it could massively increase the size and volume of the average space station in Earth orbit.
Conclusion
Just a few months ago Sierra Space completed another Ulitmate Burst Pressure test and now is moving on to larger inflatables. This joins the other full-scale UBP test passing both times by 27% at first and then 22%. Even still, there’s a lot to be done before we see these inflatables in space with humans inside.