On-Orbit Assembly Strategies for Human Space Exploration
- Paper number
IAC-05-D3.3.05
- Author
Ms. Erica Gralla, Massachussets Institute of Technology (MIT), United States
- Coauthor
Dr. Olivier de Weck, Massachussets Institute of Technology (MIT), United States
- Year
2005
- Abstract
The Arianespace launcher family will grow with the addition of Vega, the new light vehicle that will enter service in 2009 at the Europe’s Spaceport in French Guiana. Joining Ariane 5 and Soyuz, Vega is designed to provide new launch opportunities for small, mini and micro satellites.
The paper first gives an insight into the main characteristics and capabilities of the launch vehicle. The flexibility of the vehicle, fitted to cover a wide range of missions, is demonstrated through the presentation of analyses performed by Arianespace for various missions:
- AEOLUS spacecraft to be injected into a near Sun-synchronous orbit,
- LISA Pathfinder mission to be launched into an elliptic low-inclination transfer orbit,
- SWARM mission consisting in three satellites in near polar low orbits.
The crucial role to be played by Vega in ensuring an affordable access to space for a wide range of small missions is then addressed while keeping in mind two significant drivers:
- Small spacecraft can nowadays achieve complete missions and should therefore be offered dedicated services instead of being bound to fly as secondary payloads;
- The key to mission success starts with the launch phase, one of the most important and sensitive part of the whole mission.
Based on the projection of the Low Earth Orbit satellite launch market for the coming years, an assessment of Vega launch solutions for small, mini and micro satellites serving science, technology and exploration is discussed.
Finally, the Arianespace management of Vega exploitation in synergy with Ariane 5 and Soyuz is presented. It is shown that a consistent and standard approach for the three launch systems will be implemented, thus improving quality and efficiency thanks to other launchers experience.
In recent years, human space exploration programs such as the Shuttle and the International Space Station (ISS) have been plagued by political and technical problems as well as soaring costs. In order to avoid such difficulties, next-generation human space exploration programs should be designed for both sustainability and affordability. By viewing exploration programs as a "system-of-systems," we can focus on reducing costs through the use of flexible, reusable infrastructures to support various aspects of manned spaceflight. One of the most difficult pieces of this system-of-systems is the issue of access to space. Current evolved expendable launch vehicles (EELV’s) can loft only about 25 metric tons into low Earth orbit (LEO); however, human lunar or Mars exploration will require spacecraft many times that size. Prior work on optimal launch vehicle sizing explored the launch vehicle tradespace, concluding that a "best" launcher size exists (around 60 mt for our reference transportation architecture). While the launch vehicle sizing trade is relatively well understood, the other key piece of the puzzle has been given much less attention. On-orbit assembly of separately launched components is an equally important component of the infrastructure enabling human access to space. This paper addresses this deficiency by examining the combined launch and assembly tradespace, with the goal of understanding how various on-orbit assembly strategies can enhance the sustainability and affordability of human space exploration.
To that end, trade studies are performed using various launch scenarios and assembly strategies. On-orbit assembly can be accomplished through three distinct methods:
- Self-assembly: Each module performs its own rendezvous and docking operations.
- Module as tug: A single module collects and assembles the remaining modules.
- Space tug: Dedicated tug module waiting in orbit collects the modules.
The main advantage of the tug cases is that each separate module does not require its own propulsion and guidance/control capabilities, reducing the module mass and complexity. In addition, the dedicated tug case would establish a flexible, reusable assembly infrastructure for use in later missions.
A detailed model is developed to compare these assembly strategies for various launch scenarios (launch vehicle size, reliability, schedule) and vehicle scenarios (number of modules, mass, propulsion systems). Based on a detailed operations concept and orbital dynamics model, we compute the time and propellant required to assemble all components in each case. By comparing these metrics across all launch and vehicle scenarios, we can understand how various assembly strategies impact launch scheduling and mass requirements. Finally, sensitivity analysis is performed in order to determine the driving factors (e.g. number or size of modules) for choosing one assembly strategy over another, and to understand the impact of parameters such as launch dispersion and propulsion type.
Results show that assembly strategy has a significant impact on overall launch mass and launch scheduling. Therefore, the design of a sustainable human space exploration system-of-systems should take into account the assembly requirements as a key component of the launch infrastructure. When combined with modular spacecraft design, investment in a reusable tug-based assembly infrastructure could enable new mission concepts and enhance the sustainability and affordability of human spaceflight programs.
- Abstract document
- Manuscript document
IAC-05-D3.3.05.pdf (🔒 authorized access only).
To get the manuscript, please contact IAF Secretariat.