While waiting for all the remaining parts for the Tycho Deep Space capsule it is a good time to attack all the other issues such as buoyancy, hatch, control panels, parachutes and more.

One subsystem is very dear to me: the seat. As an architect I am always very excited about this. The seat is what specifically distinguishes payload spaceflight from human spaceflight. It is the vital part that integrates a human being with the machine. Except in space station missions the seat is where you live, eat, enjoying the calls of nature, control your flight and hopefully enjoy the entire ride, the entire time.

Your memory of going into space and back to earth will be centered on you location and how it felt both mentally and physically. The seat is essential to all this.

Figure 5.3.1-1 Acceleration Environment Coordinate System Used in NASA-STD-3000. NASA

In human spaceflight you tend to place your astronauts on their backs. The reason for doing this is very simple and based on the high tolerance of acceleration (g-force) in that specific vector (see images right 5.3.1-1 & 5.3.3.1-1) [1]. But as you also see in the NASA images below acceleration must always be addressed related to time. High acceleration can be harmless during a short time frame where as low acceleration (even standing up, 1 G) can be harmful for a long period of time.

With the acceleration vs time aspect in mind you will find that we made our first spacecraft and seat with the astronaut standing up. This is actually possible when having low acceleration for a “short” period of time besides not having a bigger rocket. I will get more into the details of the first spacecraft named Tycho Brahe-1 in future blog posts.

But for the Tycho Deep Space (half sized Apollo CM) capsule, being developed right now, we have enough room to go the oldschool way and the major design of the seat design lines are somewhat derived from the Apollo seating system.

When I design a seat for a spacecraft I work with this basic design topography:

Figure 5.3.3.1-1 Linear Acceleration Limits for Unconditioned and Suitably Restrained Crew members. NASA

1. Context or base:

Something is holding on to the seat. In this case it is our spacecraft. The shape of the interior construction and distribution of subsystem has a major impact on how and where a seat can be placed. The final position and orientation must satisfy functions like window outlook, easy ingress/egress, control panel operation, natural or induced acceleration etc.

2. Acceleration/impact:

The connection between the seat and the spacecraft may require control of natural or induced accelerations and vibrations in vectors related to the mission scenario. There are numerous systems that can handle this. And example could be struts, wire rope insulators, elastic bands, foam and water.

3. Seat main frame:

Something has to hold the seat together. It could be a basic iron or aluminum frame holding on to the struts or directly to the spacecraft. I like plain carbon steel.. for now. This basic frame only needs to have a low detailed ergonomic shape for the human body.

4. Human ergonomics, seat/human:

I recommend having something between the astronaut and the basic seat frame. Adding this layer gives you less requirements of the basic seat frame detailing and a way to create your final ergonomic fit for the astronaut. This layer could be a detailed shaped carbon fiber sheet or a foam coating. I like working with memory shape foam which is easy to shape, add and provides me with a great ergonomic comfort. It really doesn’t matter if you where nervous before a flight and ate too many burgers. Your recently appeared love handles will be well met by the memory shape foam.

5. Final fabric coating:

I prefer having a nice fabric coating on the ergonomic layer especially on foam. A correct fabric gives you the final snazzy look but also makes your seat foam breathe and prevents you from sweating too much while being in the seat for hours or even days.

So far the seat main frame has been created in plain carbon steel to fit the basic requirements of astronaut orientation, window outlook, control panel operation and ingress/egress. The orientation of the seat inside the space capsule can be seen here.

Welding basic seat frame. Image: Copenhagen Suborbitals

Final basic seating frame and crash test dummy Randy. Image: Kristian von Bengtson

I have been around several ideas of acceleration control ranging from long dampening struts, air-cylinders, elastic bands, foam and more. A few months back I snuck on board a Royal Danish battle ship and found a possible solution: wire rope insulations. They are used to hold delicate equipment preventing acceleration and vibration. Such a system is able to deal with specifically known impacts in all directions and could be the connection point between the spacecraft and seat main frame while handling acceleration during launch and splashdown. So, for now I hope it can be a solution to this issue.

Right now I am sketching different ways to add my memory shape foam to the main frame for final ergonomic comfort. When I have settled for a design and production method I will begin this coating process.

Memory shape coating sketch. Image: Kristian von Bengtson

The seat passed its first initial test yesterday. I dragged in into the space capsule, placed to lose sheets of memory shape foam and unintentionally fell asleep for an hour. It was nice and comfy.

It is going to be a great ride.

Ad Astra
Kristian von Bengtson

ref:
[1] NASA, MSIS, Volume I, Section 5 NATURAL AND INDUCED ENVIRONMENTS