A chair for Martian gravity

The challenge

Analog habitats today just use standard Earth furniture, which doesn't survive the economics of Mars. And at about a third of Earth's gravity (0.38 g), posture, support, and rest all change : so the real question isn't how to ship a chair, but what a chair should even be on Mars.

Approach

Led by Anastasia Prosina with Robert Salazar and Samuel Binkin at the Sasakawa International Center for Space Architecture (SICSA), the study designed flexible, multipurpose furniture that adapts across independent work, conference, social, and dining modes : on the principle that space architecture defines behavior. Everything was designed around the body's real needs at 0.38 g rather than transplanting an Earth chair to another planet.

What we built

The deployable adjustable workstation is a sandwich of two UHMWPE polymer sheets around a closed-cell foam board : stain-resistant, lightweight, high tensile strength, and no water maintenance. The ultralight collapsible chair uses carbon-fiber telescopic poles, UHMWPE connectors, a polyurethane-foam seat, silicone foot pads, and upholstery combining nylon with antimicrobial Merino wool.

Outcome

The chair weighs 1.5 pounds : 75% lighter than a typical office chair : and four units pack into just two cubic meters. Its 110° trunk-thigh angle keeps muscles engaged, helping counter the bone and muscle loss of low gravity. A design study that treats everyday furniture as a serious space-architecture question.

Why furniture is the problem

The greatest challenge in planning and designing Mars habitats is that anything delivered from Earth must travel to the surface on an extensive, expensive transportation system.

How we outfit Martian habitats with efficient furniture has not been widely addressed. Earth-based analogs, NEEMO underwater, HI-SEAS in Hawaii, the Mars Desert Research Stations in Utah, are furnished with wooden tables and metal-framed elements anyone could find at home. It is unlikely those everyday furnishings will be used in space habitats: furniture in surface habitats is one of the main mass contributors, taking up around 20 to 30 per cent of habitat volume.

It costs $783,000 to send one office chair to Mars. A typical office chair weighs 6.6 pounds, at about $118,600 per pound to Mars, based on an Atlas V 541 at roughly $235 million.

Concept

Space architecture defines behavior. The research focused on furniture that follows the ergonomics of a person on the Martian surface while supporting wellbeing, with textures, colors and light that compensate for what is missing.

We took a twenty-six-foot habitat with pre-integrated engineering systems and looked at how to outfit that small volume with elements that could be arranged flexibly and serve more than one purpose: independent work, conference tag-ups, social gathering and dining, breaking the monotony of a small space.

Deployable multipurpose desks, chairs and a galley increased the flexibility of the interior while cutting mass, volume and overall mission cost. Easily maintainable materials such as antimicrobial surfaces also reduce the use of a scarce resource: water.

Posture on Mars

Biomechanical posture is the primary driver of designing any furniture. On Mars the measurements and proportions of the body stay as they are on Earth. Its shape and size would not change, though there might be slight spinal elongation, less than 3 per cent of what zero gravity produces.

But 37 per cent of Earth's gravity, 3.711 m/s² against 9.8, will affect the comfort of certain poses and positions. Dynamic movement changes too: walking and running differ as they do on the Moon, though less so, since Mars has more gravity than the Moon's 1.62 m/s².

Deployable adjustable workstation

Workstations are a core piece of the problem: astronauts spend most of their time working, up to eight or nine hours. The workplace has to be efficient with space, easy to use, routinely maintained and ergonomic.

Ours is a deployable system working in three modes: fast tag-ups, independent work and social gathering, and it doubles as collaborative furniture.

It is made of a sandwich of two UHMWPE polymer sheets with a closed-cell foam board between them. Fabric was not an option, since it would need water, a scarce resource. UHMWPE is stain proof and not chemically reactive, with the highest abrasion resistance of any polymer, light, and exceptionally strong in tension. A sheet need only be 1/32 in thick and still resist cutting.

Ultralight collapsible chair

The chair height adjusts to the workstation depending on the task. With the workstation standing, the saddle chair gives a tall, wide stance like horseback riding, opening the hips and knees and encouraging the spine into its most natural curve.

Low gravity dissolves muscle and bone. To reduce that and allow a safer return to Earth, the chair revises how one sits: a 110-degree trunk-thigh angle leaves a slight imbalance in the resting position, which keeps the back and leg muscles working. It is subtler than exercise or electrical stimulation, but it is an additional noninvasive measure.

The plus-shaped back allows comfortable backward or sideways sitting, and the contoured saddle seat opens the hips for a more active forward posture while leaving room behind for conventional sitting. Height and sitting angle adjust to the crew. Four chairs stow in two cubic meters at 1.5 pounds each, 75 per cent lighter than a typical office chair.

It is built from carbon fiber telescopic poles with UHMWPE connectors that hold the poles in compression, adding rigidity with less material. The polyurethane foam seat is light and durable, with silicone foot pads to stop it sliding. The upholstery is nylon mixed with Merino wool, strong, abrasion resistant and antimicrobial, with texture finishes designed to wake up the tactile senses of a crew with little access to nature or human touch.

Team. Anastasia Prosina, Robert Salazar, Samuel Binkin. Client: Sasakawa International Center for Space Architecture, 2019.