The ARCHIMEDES design has been developed, based on the ballute and mission requirements, in the frame of a doctorate thesis, accompanied by an extensive research and test program including scientific analyses, technology development for the ballute and the associated spacecraft systems, and a series of ground and flight tests.
Due to the complexity of the ARCHIMEDES space vehicle is was concluded, that a flight simulation on Earth would be necessary simulating the Mars vehicle as closely as possible. This was the origin of the Miriam-2 flight test program. A partnership was established with the German Sounding Rocket Test Centre DLR-MoRaBa near Munich for a sounding rocket flight campaign transporting a space vehicle as similar as possible to the ARCHIMEDES Mars vehicle far beyond the Earth atmosphere allowing to deploy, inflate and release a ballute with a scientific payload (pod) before it would enter in the upper thin Earth atmosphere under similar atmospheric conditions as would the Mars balloon in the Mars atmosphere.
Due to the mass and volume constraints of the sounding rocket, but also due to the limitations of testing a large ballute on Earth prior to the mission, it was decided to reduce the size of the ballute and its associated systems for Miriam-2 by a factor of 1:2,5, corresponding to a ballute diameter of 4 m compared to the 10-m, ballute for the Mars mission. In order to reproduce the dynamic behaviour of the ARCHIMEDES ballute as far as possible, the relation between the masses of the balloon and the pod should be maintained as far as possible (refer to the table). The Miriam construction should be identical to the ARCHIMEDES design as far as possible considering the reduced size.
The ARCHIMEDES and Miriam-2 design must satisfy a series of conditions imposed by the mission:
- development of a ballute surviving
- an 8 months transport to Mars in densely packed conditions (for Miriam-2 the storage time would be shorter corresponding to the time between integrating Miriam-2 with the sounding rocket in Germany and the launch some weeks later in Kiruna in Northern Sweden)
- deployment, inflation and release of the ballute in space before the start of the actual scientific mission
- the aero-thermal loads occurring at entry
- development of all the corresponding on-board equipment respecting the mass and volume constraints of the P5-A satellite
The ballute development presents the most significant challenge, since never before has a balloon been developed meeting similar conditions. Areas requiring specific attention are:
- selection of material withstanding storage and entry conditions
- achieving a spherical form (no. of segments, segment assembly accuracy etc.)
- achieving tightness
- ballute manufacturing technologies
- cutting of segments
- welding of segments
- integration of pod and inflation hose ("windsock")
- deployment and inflation of the ballute after 8 months of storage and development of the corresponding equipment ensuring the ballute integrity
- ground tests of the ballute under conditions as similar as possible to the flight conditions
Therefore both ARCHIMEDES and Miriam are composed of the following major elements:
- the ballute consisting of the balloon and an instrument and avionics carrier (pod) integrated into the balloon skin
- the ballute storage system in which the ballute is transported to Mars and then deployed for the subsequent inflation
- the balloon inflation system to inflate the ballute in a Mars entry orbit
- the system releasing the inflated ballute
- the corresponding avionics
- the scientific instruments foreseen for the Mars mission should be identical in order to test their functions during the critical atmospheric entry flight phase
The attached images show the actual Miriam-2 design. ARCHIMEDES equipment would be functional identical, if the Miriam-2 mission would demonstrate its validity, but more performant for meeting the requirements for a larger balloon. The necessity to use materials and components surviving the space environment may lead to further changes.