Overview

Peter Langkjær Madsen (born 12 January 1971) is a Danish former entrepreneur and self-taught engineer who gained public attention for constructing home-built submarines and participating in amateur rocketry. He co-founded the volunteer-run space project Copenhagen Suborbitals and ran a small engineering company, RML Spacelab ApS. In April 2018 he was convicted in Denmark of the 2017 murder of Swedish journalist Kim Wall on board his submarine UC3 Nautilus and was sentenced to life imprisonment.

Engineering activity and public profile

Madsen built and worked on a variety of private projects that combined maritime and aerospace interests. He presented himself as a hands-on inventor and drew attention from hobbyist communities and local media for unconventional, do-it-yourself engineering efforts. His projects were often collaborative, involving volunteers and small teams rather than large commercial or academic institutions.

Notable projects

  • UC3 Nautilus — a privately constructed midget submarine that became one of Madsen's best-known vessels.
  • Copenhagen Suborbitals — a non-profit group co-founded by Madsen that aimed to develop amateur rockets and test vehicles for suborbital flight.
  • RML Spacelab ApS — a company Madsen established for engineering activities and small-scale projects.

Criminal case and trial

In 2017 a high-profile criminal investigation centered on the disappearance and death of journalist Kim Wall after she boarded Madsen's submarine for an interview. The subsequent trial examined forensic evidence and conflicting witness statements. In April 2018 a Danish court found Madsen guilty of murder as well as related offences; he received a life sentence. The case drew extensive national and international media coverage and raised questions about safety, accountability and oversight in privately run technical projects.

Legacy and public response

The contrast between Madsen's prior public persona as an eccentric engineer and his criminal conviction has shaped how his projects are remembered. His activities prompted renewed scrutiny of hobbyist engineering undertakings that involve significant risks, and the case influenced debates about media access to unusual private experiments. Organizations and volunteers associated with his projects distanced themselves after the events, while policymakers and commentators called for clearer safety standards and legal supervision where public safety might be affected.

Notable distinctions

Madsen is widely described as a self-taught maker who moved between maritime and aerospace interests; his conviction for a violent crime is the defining aspect of his public legacy. For further reporting and primary sources, see media coverage linked through official channels and documented court records.