Cop Sub News

Enclosure for the astronaut

Capsule graphic - illustration by Carsten Olsen
Capsule graphic – illustration by Carsten Olsen

“For a while now it has been very quiet from us when it comes to the progress of the capsule that is going to bring our astronaut into outer space. The reason for this is a lack of human resources for designing and developing the capsule.
We are trying to change that by gathering a small group of people who will have the capsule design as their primary focus. This means that we are beginning to transform some of the early sketches and models into something more tangible.

When designing a space capsule that is both safe, lightweight and actually possible for us to build, it is important to break the capsule down in sub-systems. This makes it possible to maintain the overall picture of what needs to be designed and in what order, and what influence the different systems have on each other.
Off course it is fun to go into solution mode and start detail design of little bits and pieces like safety harness mounting brackets or cup holders, but you need to maintain a view of the big picture. This is why we start by collecting all the data and results from all the work that has been done on the Spica rocket capsule these past couple of years.

We have previously worked on small scale models in free fall tests and have also had some students from the Technical University of Denmark (DTU) do a project on the ingress / egress hatch. Now we are starting full scale models.

Here are some of the first drawings of a design of the capsule for the Spica rocket
Here are some of the first drawings of a design of the capsule for the Spica rocket

The first will be a so called boiler plate model of the pressure hull made in steel. This is to use the same model for several tasks. It is being used to determine the location of systems that has to do with the astronaut. That would be things like seat design and –placement, hatch size and –placement, porthole size and –placement etc. Another thing that we can use a sturdy and rigid enough model to do drop tests, to evaluate different deformation structures. These will reduce the shock effect on the astronaut when the capsule has the splashdown when landing.

We are working on a budget and purchasing the materials for the capsule so we can begin building something tangible, so expect some small updates and pictures of the production of the model here on the site and on social media in the coming time.
When we are a bit further in the design process we will begin to add more of the identified systems to the boiler plate model. Here there is another advantage of using steel: it is easy to weld on and cut off new things.
It is still a bit to early to talk about the different systems. We will share that when we are a little further ahead.”
Martin H. Petersen, CS Capsule Lead

In Copenhagen Suborbitals


Our Nexø II rocket is ready and will be launched in the spring of 2018.

“The Nexø II rocket will be  the most advanced rocket build and launched by CS so far. The Nexø rocket class is a technology demonstrator in advance of building the significantly bigger Spica rocket that will take our astronaut to space. Thus, Nexø is an important part of the Spica roadmap and the technology developed and used in the Nexø class will be used in the Spica rocket.

Design and development

Just as Nexø I the Nexø II rocket is powered by our own BPM5 engine providing a nominal thrust of 5000 N running on ethanol and liquid oxygen. It has a body diameter of 300 mm, a total length of 6.7 m and a dry weight of about 178 kg. With a target filling ratio of 85% propellants it will carry 114 kg propellants for a Gross Lift-Off Weight (GLOW) of 292 kg.

Nexø II is actively guided by our own custom build Guidance and Navigation Computer (GNC). A set of four graphite jet vanes are used as the Thrust Vector Control system (TVC) commanded by the GNC. The system is identical to the one successfully used on the Nexø I mission. The animation below illustrates the perfect performance of the TVC system on the Nexø I rocket.

Nexø II is in many aspects identical to Nexø I, we have however implemented a few changes and newcomings:

Dynamic Pressure Regulation (DPR) including a 6000 standard liter (20 liter @ 300 bar) helium tank

Problematic LOX tank vent valve changed for cryo compatible model

LOX tank filling monitored by capacitive gauge

The main feature of the Nexø II rocket is the implementation of the DPR system. The system provides high pressure helium to the propellant tank as they are emptied in order to maintain the feed pressure and in turn the combustion chamber pressure inside the engine. This allows the engine to run at its optimal operating point throughout the entire flight.

To ensure correct filling of the LOX tank during launch preparations we have recently developed a capacitive level sensor calibrated for liquid oxygen. This will allow us to fill the LOX tank with a significantly higher accuracy than what was possible on Nexø I.

Expected flight performance

The primary consequence of the implementation of the DPR system is that Nexø II can have a higher filling ratio and better propellant efficiency than Nexø I. This means that Nexø II will have significantly more total impulse available. It is however also heavier.

With a GLOW if 292 kg and an effective thrust of 4500 N (10% lost to drag on jet vanes) Nexø II will accelerate at an initially modest 5.6 m/s^2 when leaving the launch tower. After 43 seconds of flight it will have depleted its propellants and reached a speed of 1280 km/h or Mach 1.14 at an altitude of 7 km. From here it will coast to apogee at 12.6 km. Upon descent it will deploy a ballute and parachute based landing system to land in the ocean.

Thus Nexø II is neither intended to set altitude or speed records. It is entirely a demonstrator vehicle that will hopefully show we are on track for implementing the same technology in the Spica rocket.”

In Copenhagen Suborbitals



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