The two main scientific and technological objectives of the RETALT project are:

To investigate Launch system re-usability technology of VTVL TSTO RLV
applying retro propulsion combined with the use of aerodynamic control surfaces which is currently dominating the global market.

To investigate Launch system re-usability technology of VTVL SSTO RLV
applying retro propulsion for future space transportation systems.


To meet these two objectives two reference configurations have been defined:

  • A configuration similar to the SpaceX rocket “Falcon 9” that will be the reference for the state-of-the-art TSTO RLV.

  • A configuration similar to the DC-X that will serve as reference for a SSTO RLV.


The objective of the project is to raise the Technical Readiness Level (a measure of 1 to 9 of how far a technology is away from market readiness) up to 5 for most of the technologies investigated in the project and up to 3 for the Guidance and Navigation and Control system. The partners strive for concepts of reusable launch vehicle that best combine all the investigated technologies in a single design.


We are convinced that it is absolutely necessary to investigate Retro Propulsion Assisted Landing Technologies to make re-usability state-of-the-art in Europe. The know-how for a rapid application of re-usability in European launchers can only come from a strong common effort of research and industry. Once re-usability has become the state-of-the-art in Europe it will impact not only the scientific community and industry of space technologies but each European citizen, as launch technologies will become more affordable and new space debris can be avoided. Additionally, the technologies investigated can be applied in other research areas and industrial sectors.





The overall objective of the RETALT project will be to investigate Launch system re-usability technologies of VTVL TSTO and SSTO RLV applying retro propulsion using two configurations: RETALT1 and RETALT2.

The concept of retro propulsion assisted vertical landing is simple in terms of number of parts needed and in the design. However, it is complex regarding the aerodynamics, aerothermodynamics and thus the flight dynamics of the vehicle. Furthermore, innovative GNC concepts, structures and mechanisms and TPS need to be developed. These fields have been identified for the study of key technologies in the RETALT project.

To obtain a well-structured work flow the project activities are grouped in the following work packages.

WP1: Coordination and Management

WP leaderDLR

WP contributors: CFS Engineering, Elecnor Deimos, MT Aerospace

WP objective:

This work package is responsible for coordinating the project from both the administrative and the technical perspectives, aiming towards achieving effective operation of the project as well as timely delivery of quality results. It covers the overall administration and management of RETALT with the following aims:

  • Ensure meeting the objectives as defined in the project plan;

  • Keeping the project schedule and guarantee the execution of the work plan and the achievement of the project goals on time and within budget;

  • Establishment of appropriate review procedures within the project;

  • Establishment of an efficient system of communications and conflict resolution procedures, also by means of collaborative environment tools to support consortium interactions;

  • Planning, monitoring and controlling project progress and outputs, and taking corrective actions;

  • Administration of the contract and project financial management;

  • Preparation of progress and management reports and reporting to the EC;

  • Coordination of participation and contribution to external events, including relevant workshops and conferences;

  • Overall quality assurance.

WP2: Reference Configurations

WP leaderDLR

WP contributorsALMATECH, MT Aerospace

WP objective:

The main objective of this WP is the definition of the reference configurations, which will be used as baseline for the technical work packages.

WP3: Aerodynamic and Aerothermal Loads

WP leaderDLR

WP contributorsCFS Engineering

WP objective:

The objectives of this WP are experimental and numerical investigation of aerodynamics and aerothermal loads of both RETALT1 and RETALT2 configurations and creating AEDB and ATDB for the flight dynamic analysis.

WP4: Flight Dynamics and GNC

WP leader: Elecnor Deimos

WP contributorsDLR, CFS Engineering

WP objective:

The objectives of this WP are flight dynamic analysis of the RETALT1 and RETALT2 configurations and definition of GNC and control rules.

WP5: Structures and TPS



WP objective:

The objectives of this WP are the design of structural components, TPS and health monitoring instrumentation of both RETALT1 and RETALT2 configurations and manufacturing of test models and ground demonstrators.

WP6: Dissemination and Exploitation


WP contributorsDLR, ALMATECH, AMORIM, Elecnor Deimos, MT Aerospace

WP objective:

The objectives of this WP are to ensure that the results obtained in the RETALT project are widely communicated and to prepare the exploitation plan of these results. To this goal, the WP is organised around the following detailed actions:

  • To prepare and implement a strategy for the exploitation of the project results;

  • To ensure the communication and dissemination of the project, its results and achievements towards the target groups identified in Section 2;

To monitor the projects results for possibilities of IPR protection and Innovation potential (IPR and Innovation Management Team).

WP7: Ethics Requirements

WP leaderDLR

WP contributors: ALMATECH, AMORIM, CFS Engineering, Elecnor Deimos, MT Aerospace

WP objective:

The objective is to ensure compliance with the ‘ethics requirements’ set out in this work package.



During the three years of the project lifetime the consortium will investigate the areas of aerodynamics, aerothermodynamics (i.e. the temperatures that evolve at the surface of the vehicle during flight), flight dynamics, guidance, navigation and control, and advanced structural parts, materials and mechanisms. For this purpose, two types of rocket launchers will be investigated which both start and land in an upright position. One of them will have two stages and will be similar to conventional rockets like the Falcon 9 or the Ariane 5 (RETALT1 concept). For this launcher only the first stage will be landed again. The second launcher has only a single stage (RETALT2 concept). It will be designed for the use of smaller payloads and when returning it will break not only with retro propulsion but also with the aid of a large aerodynamic base surface at the bottom.

These rockets will not really be launched; however, they will be used as the reference configurations for the investigations of the different technologies in the project. Aerodynamic wind tunnel experiments, numerical simulations and ground tests of several components will serve to verify the outcomes of the project.


Conceptual sketch of the RETALT1 spacecraft. Configurations from left to right: launch, stage separation, first stage descent, first stage landing.


Conceptual sketch of the RETALT2 spacecraft. Configurations from left to right: launch, descent and landing.