Spacecraft | EPFL Graph Search

A spacecraft (: spacecraft) is a vehicle that is designed to fly in outer space and operate there. Spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, planetary exploration, and transportation of humans and cargo. All spacecraft except single-stage-to-orbit vehicles cannot get into space on their own, and require a launch vehicle (carrier rocket). On a sub-orbital spaceflight, a space vehicle enters space and then returns to the surface without having gained sufficient energy or velocity to make a full Earth orbit. For orbital spaceflights, spacecraft enter closed orbits around the Earth or around other celestial bodies. Spacecraft used for human spaceflight carry people on board as crew or passengers from start or on orbit (space stations) only, whereas those used for robotic space missions operate either autonomously or telerobotically. Robotic spacecraft used to support scientific researc

Preliminary Design of a Lunar Reconnaissance Drone

Thomas Pfeiffer, Erik Uythoven

In this report, a preliminary design study of a compact lunar reconnaissance drone module which will assist exploration rovers is presented. It is designed to assist future exploratory rover missions in difficult environments such as PSRs or extreme topographies. Although similar concepts have been validated on Mars by NASA’s Ingenuity helicopter, only few such ideas exist for lunar applications. The main challenges of this project lie in the propulsion system to be used, the thermal system of the drone (due to extreme temperatures) and the 3D mapping of the lunar surface using a flash lidar system. These aspects were studied in detail with promising results: For a drone with a weight of 20 kg, 1 kg of green monopropellant is sufficient to cover a distance of a least 1 km before it needs refuelling. In this report, it is assumed that the lightweight flash lidar technology should be developed enough to allow for 10 cm resolution at 50 m flight altitude. This feasibility and initial design study sets a foundation for lunar drones and exploration of the Moon using flying spacecrafts, although many open questions remain to be solved and detailed designs to be performed.

2022

Realization of a solid-propellant based microthruster using low temperature co-fired ceramics

Yannick Fournier, Thomas Maeder, Peter Ryser, Jaya Thakur

The introduction of micro-spacecrafts in the space industry has led to the development of various micro-propulsion techniques. Microthrusters are micropropulsion devices used in a microspacecraft for precise station keeping, orbit adjustment, attitude control, drag compensation and apogee kicking. The principle of operation of a solid propellant thruster is based on the combustion of a solid energetic material stored in a microfabricated chamber. In the current work, Low-Temperature Co-fired Ceramic (LTCC) technology has been used for the realization of a solid propellant based microthruster structure. Hydroxyl Terminated Poly-Butadiene/Ammonium Perchlorate (HTPB/AP) is used as the propellant. It is shown that geometric and dimensional variations in design, depending on the application requirements, can be easily implemented. Preliminary testing for micro-combustion has been done to verify the basic operation of the microthruster. A thrust value of 19.5 mN has been measured.

2010

GPS based navigation performance analysis within and beyond the Space Service Volume for different transmitters’ antenna patterns

Paul David Blunt, Cyril Botteron, Vincenzo Capuano, Pierre-André Farine, Endrit Shehaj

In the last years, Global Navigation Satellite System (GNSS) based navigation in high earth orbits (HEOs) has become a research field of interest, since it can increase the spacecraft’s autonomy, reducing the operating costs. However, the GNSS availability and the GNSS-based navigation performance for a spacecraft orbiting above the GNSS constellation, is strongly constrained by the signals’ power levels at the receiver position and by its sensitivity. The simulated level of signal power at the receiver’s position may considerably increase or decrease when assuming different gain/attenuation values of the transmitter antenna for a certain azimuth and elevation. Assuming a slightly different antenna pattern, therefore may significantly change the simulated signal’s availability results and accordingly the simulated navigation accuracy, leading to an inexact identification of the requirements for the GNSS receiver. This problem concerns particularly the case of orbital trajectories above the GNSS constellation, where most of the signals received are radiated from the secondary lobe of the transmitters’ antennas, for which typically very little information is known. At the time of this study, it was possible to model quite accurately the GPS L1 antenna patterns for IIR and IIR-M Blocks because of the precise information available. No accurate information was available for the GPS L1 antenna patterns of IIF Block. Even less accurate information was available on the GPS L5 antenna patterns. In this context, this paper aims at investigating the effect of different antenna pattern assumptions on the simulated signal availability and on the consequent simulated navigation performance of a spaceborne receiver orbiting in a very highly elliptical orbit from the Earth to the Moon. Initially the impact of averaging the transmitter’s antenna gain over the azimuth, typical assumption in many studies, is analyzed. Afterwards, we also consider three different L5 antenna patterns assumed in the literature (the precise pattern are unfortunately not yet fully available). For each of the considered antenna pattern assumptions, we simulate received signal power level, availability, GDOP and navigation accuracy, in order to evaluate their different effect. Finally, once identified the most conservative assumptions for the transmitters’ antenna patterns, for each elevation of the receiver antenna, we also compute the number of available GNSS observations and we analyze their distribution.

2017

GPS based navigation performance analysis within and beyond the Space Service Volume for different transmitters’ antenna patterns

Paul David Blunt, Cyril Botteron, Vincenzo Capuano, Pierre-André Farine, Endrit Shehaj

2017