Copenhagen Suborbitals is a crowd-funded human space program. It has flown six home-built rockets and capsules since 2011. The organization successfully launched its Nexø II rocket in the summer of 2018. Its stated goal is to have one of its members reach space (above 100 km) on a sub-orbital spaceflight. The organization was founded by Kristian von Bengtson and Peter Madsen.

As of September 2024, the program has 63 volunteers who elect a chairman and board members at their annual general assemblies. The chairman is Jørgen Skyt.

Copenhagen Suborbitals was founded in 2008 by Kristian von Bengtson and Peter Madsen as a non-profit, crowd-funded project that discussed most of their operations on blogs and lectures.

On 23 February 2014, the board of Copenhagen Suborbitals announced that Kristian von Bengtson had left the group, after falling out with Madsen. Madsen left in June 2014.

In 2014, Copenhagen Suborbitals designed a basic first crewed rocket and space capsule. They named it Spica, and it is planned to stand 12–14 m tall with a diameter of 950 mm. As of late September 2024, two pressure hardened 950mm steel tanks have been constructed and the development of the BPM-25 engine class is well underway.

Originally, the Spica rocket was planned to be powered by the BPM-100 class, but due to internal manufacturing troubles, the BPM-25 was eventually decided on as the engine to power the rocket. Though it is weaker, it provides several advantages through greater roll authority and flow control. The BPM-25 engines, unlike the BPM-100, will have to be clustered in order to achieve the necessary thrust to launch Spica to the desired altitude. The BPM-25 provides 25 kN of thrust. Similar to the BPM-100 engine, it uses liquid oxygen as oxidizer and ethanol as fuel. Spica will maneuver by thrust vectoring on its BPM-25 engines.

The rocket will be fully guided by home-built electronics and software. Many of the systems and technology planned for use on this rocket were previously tested and proven on the smaller Nexø class rockets in during the 2016 to 2018 period. The space capsule will be of a tubular design similar to its predecessor Tycho Brahe. While the Spica capsule has not entered more than marginal construction as of 2024, CS plans on first building a boilerplate capsule to test on the ground before moving onto the real article.

During the 2016-2018 period, the group designed, built and tested a series of smaller engines with a nominal thrust of 2 and 5 kN - the BPM(Bi-Propellant Motor)-2 class and BPM-5 class respectively. Nexø I launched under the power of a BPM-5 on July 23rd, 2016. On August 4, 2018, just as the Nexø I, Nexø II was launched under the power of a BPM-5. The Nexø class was primarily intended to serve as a technology demonstrator ahead of the development of Spica. The BPM engines are bi-liquid rocket engines using LOX and ethanol, regeneratively cooled by the ethanol fuel.

The BPM-2 was primarily intended to serve as a test article for the CS test stand and manufacturing methods, and was never intended to launch a rocket. The BPM-2 engine was static fired 4 separate times on May 2nd, 2015.

The tests were successful, with results exceeding expectations. Different fuel additives (such as TEOS) as well as different jet vane materials were also tested. The 2015 test firings used passive pressure blow-down.

No more development or use for BPM-2 or -5 engines is planned. CS has primarily moved on to the use of the BPM-25 ahead of the planned development of the Spica rocket.

From 2008 to 2012, the group based the work on a hybrid rocket, using liquid oxygen (LOX) as oxidizer. Originally, the HEAT-1X rocket was to be fueled by paraffin wax, but a ground test 28 February 2010 revealed that some of the paraffin wax had only partially melted, instead of evaporating. The result was that HEAT-1X had less power than expected. A ground test firing of HEAT-1X-P (P for polyurethane) was conducted 16 May 2010. The polyurethane had the impulse required, but showed heavy oscillation. Until 2011 the group had performed more than 30 tests of various engine types at their rocket engine test facility at Refshaleøen. In fall of 2012 a concept engine using white fuming nitric acid and furfuryl alcohol was tried using a static test setup. In 2012 a decision was made to switch to bi-propellant, liquid-fueled engines running on liquid oxygen and ethanol. This evolved into the BPM(Bi-Propellant Motor) class currently in use at CS as of 2024.

The HATV (Hybrid Atmospheric Test Vehicle) was a planned sounding rocket. The HATV booster was successfully static fired, though it was never launched.

HEAT 1X (Hybrid Exo Atmospheric Transporter) was the rocket booster module intended to launch the space capsule Tycho Brahe into space, the combination being known as HEAT-1X TYCHO BRAHE. The rocket design was the result of numerous static-booster tests of the solid fuel epoxy and the liquid oxidizer nitrous oxide. A combination which was also used in the scale-down test rocket HATV (Hybrid Atmospheric Test Vehicle) which was only one third the size of the HEAT. Stabilization of the rocket was provided through rollerons. The rocket was launched on June 3rd, 2011. from the floating Sputnik platform.

Within the first few seconds the rocket unexpectedly began to pitch over to approximately 30 degrees to horizontal. Due to the undesirable angle, the motor was manually commanded to shut down 16 seconds into flight at an altitude of 1.4 kilometers, with the rocket eventually rising to an apogee of approximately 2.8 kilometers, significantly off from the 30km goal. The rocket landed 8.5 kilometers away from the position where it was launched. The Tycho Brahe successfully separated from the booster, however, both the parachutes for the booster and Tycho Brahe did not successfully deploy. In the case of the Tycho Brahe, it was successfully recovered from the ocean after suffering a 26G impact upon landing. It was found waterlogged and partially damaged. The booster sank to a depth of 80-90 meters.

TM-65 and TM6-5 IIA/B were liquid propellant engines using 75% Ethanol and liquid oxygen (LOX) as oxidizer. These engines produced about 65 kN thrust. First static tests were conducted in May 2012. One TM65 II engine was for HEAT-2X and one was for HEAT-1600 LE. The TM-65 engine passed the test undamaged, and was fired at up to 50% of its rated thrust. The group planned to repeat the test with higher thrust levels, until the TM-65 class in 2014 was abandoned in favour of the BPM-100 engine concept.

The HEAT-2X was a rocket built for flight-testing the TM-65 engine. It was planned to carry a 1:3 scale, 80 kg space capsule mock-up called the TDS-80 into the stratosphere above the Kárman Line.

The rocket was not flown as it suffered an engine fire during a static test in the summer of 2014. The rocket nozzle imploded and a welding seam opened resulting in the expulsion of all the ethanol fuel (some 500 L) in just three seconds resulting in a large fire which damaged part of the rocket. The engine failure and subsequent fire was filmed up close with a high-speed camera, which although burned on the outside, survived the inferno enough for the film to be recovered. The fire damaged the onboard TM-65 engine enough to be unrepairable, leading to both the engine and HEAT-2X as a whole being retired to the CS museum. This was one of the major deciding factors in choosing to retire the TM-65 class.

The Recruits Initiative, launched in 2021, was designed to attract and educate talented young individuals in the fields of rocket science and technology. The initiative also aimed at enhancing Danish expertise within the space and defense industries by fostering the development of skilled professionals. This project contributes to the success of the Spica project and it also strengthens the competitiveness of Danish businesses in the growing global space industry.

The Recruit Rocket is a single-stage rocket designed and developed by the recruits team at Copenhagen Suborbitals. The rocket measures 5 meters in length from nose to engine, with a total weight, including fuel, of approximately 165 kg. Instead of a turbopump, it is powered by a dynamic pressure-regulating system (DPR). The BPM5 engine has been refined to the maximum during the rocket’s development, and through optimizing the design, it has achieved an impressive performance of 10 kN. The rocket’s top speed with a 5 kN motor is estimated to be 475 m/s, which is 1710 km/h. The project has provided a unique opportunity for the new members to gain hands-on experience, not only with the fundamental aspects of rocket design but also equipping them with the ability to tackle the various challenges that arise during rocket projects. As of 2024, the rocket is set for static testing in early 2025.