ArianeGroup and SSC Space conducted a rehearsal on 23 July at the Esrange Space Center in Sweden to practice countdown and post-flight procedures for the Themis rocket prototype. The mission aimed to identify any remaining anomalies prior to flight. [claim:3, claim:4]
Themis is an ESA rocket prototype serving as a European demonstrator for low-cost rocket recovery and reuse technologies. It stands as the first full-scale demonstrator for a reusable European main stage. [claim:1, claim:11]
Cryogenic Testing and Safety
During the rehearsal, the prototype was filled with liquid nitrogen cooled to –200°C. While liquid oxygen is typically cooled to –183°C, liquid nitrogen was used for this specific test because it is non-flammable and non-explosive, despite sharing similar density and cryogenic temperature properties with the intended propellants. [claim:5, claim:6, claim:9]
Temperature of the liquid nitrogen used during the Themis rehearsal.
The rocket is powered by the Prometheus engine, which utilizes liquid oxygen and liquid methane as propellants. This combination differs from the Ariane 6 main engine. Methane offers advantages over kerosene and liquid hydrogen, as it delivers higher performance than kerosene and does not require the extreme cooling necessary for liquid hydrogen. Additionally, methane is a larger molecule that is easier to handle and less likely to leak. [claim:2, claim:8, claim:10]
The Prometheus engine produces the same thrust as the main engine used on the Ariane 6 heavy-lift rocket. [claim:7]
Project Development and Funding
Themis was developed under the European Space Agency (ESA) future Space Transportation preparation programme. ArianeGroup serves as the prime contractor alongside multiple European industrial partners. [claim:12]
The launch campaign is being carried forward by the Horizon Europe project SALTO. This project is funded by the European Commission as part of the EU Space Research and Innovation Work Programme. [claim:13, claim:14]
Managed by the EU executive agency HaDEA, the SALTO project involves 25 consortium partners from 12 European Union countries. [claim:15]