TY  - CHAP
A1  - Dachwald, Bernd
A1  - Wurm, P.
T1  - Mission analysis for an advanced solar photon thruster
T2  - 60th International Astronautical Congress 2009, IAC 2009
N2  - The so-called "compound solar sail", also known as "Solar Photon Thruster" (SPT), is a solar sail design concept, for which the two basic functions of the solar sail, namely light collection and thrust direction, are uncoupled. In this paper, we introduce a novel SPT concept, termed the Advanced Solar Photon Thruster (ASPT). This model does not suffer from the simplified assumptions that have been made for the analysis of compound solar sails in previous studies. We present the equations that describe the force, which acts on the ASPT. After a detailed design analysis, the performance of the ASPT with respect to the conventional flat solar sail (FSS) is investigated for three interplanetary mission scenarios: An Earth-Venus rendezvous, where the solar sail has to spiral towards the Sun, an Earth-Mars rendezvous, where the solar sail has to spiral away from the Sun, and an Earth-NEA rendezvous (to near-Earth asteroid 1996FG3), where a large orbital eccentricity change is required. The investigated solar sails have realistic near-term characteristic accelerations between 0.1 and 0.2mm/s2. Our results show that a SPT is not superior to the flat solar sail unless very idealistic assumptions are made.
KW  - Interplanetary flight
Y1  - 2009
SN  - 978-161567908-9
N1  - 60th International Astronautical Congress 2009, IAC 2009; Daejeon; South Korea; 12 October 2009 through 16 October 2009
VL  - 8
SP  - 6838
EP  - 6851
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Schoenrock, Britt
A1  - Muckelt, Paul E.
A1  - Hastermann, Maria
A1  - Albracht, Kirsten
A1  - MacGregor, Robert
A1  - Martin, David
A1  - Gunga, Hans-Christian
A1  - Salanova, Michele
A1  - Stokes, Maria J.
A1  - Warner, Martin B.
A1  - Blottner, Dieter
T1  - Muscle stiffness indicating mission crew health in space
JF  - Scientific Reports
N2  - Muscle function is compromised by gravitational unloading in space affecting overall musculoskeletal health. Astronauts perform daily exercise programmes to mitigate these effects but knowing which muscles to target would optimise effectiveness. Accurate inflight assessment to inform exercise programmes is critical due to lack of technologies suitable for spaceflight. Changes in mechanical properties indicate muscle health status and can be measured rapidly and non-invasively using novel technology. A hand-held MyotonPRO device enabled monitoring of muscle health for the first time in spaceflight (> 180 days). Greater/maintained stiffness indicated countermeasures were effective. Tissue stiffness was preserved in the majority of muscles (neck, shoulder, back, thigh) but Tibialis Anterior (foot lever muscle) stiffness decreased inflight vs. preflight (p < 0.0001; mean difference 149 N/m) in all 12 crewmembers. The calf muscles showed opposing effects, Gastrocnemius increasing in stiffness Soleus decreasing. Selective stiffness decrements indicate lack of preservation despite daily inflight countermeasures. This calls for more targeted exercises for lower leg muscles with vital roles as ankle joint stabilizers and in gait. Muscle stiffness is a digital biomarker for risk monitoring during future planetary explorations (Moon, Mars), for healthcare management in challenging environments or clinical disorders in people on Earth, to enable effective tailored exercise programmes.
KW  - Ageing
KW  - Anatomy
KW  - Muscle
KW  - Musculoskeletal system
KW  - Physiology
Y1  - 2024
U6  - https://doi.org/10.1038/s41598-024-54759-6
SN  - 2045-2322
N1  - Corresponding author: Dieter Blottner
VL  - 14
IS  - Article number: 4196
PB  - Springer Nature
CY  - London
ER  - 
TY  - JOUR
A1  - Zhen, Manghao
A1  - Liang, Yunpei
A1  - Staat, Manfred
A1  - Li, Quanqui
A1  - Li, Jianbo
T1  - Discontinuous fracture behaviors and constitutive model of sandstone specimens containing non-parallel prefabricated fissures under uniaxial compression
JF  - Theoretical and Applied Fracture Mechanics
N2  - The deformation and damage laws of non-homogeneous irregular structural planes in rocks are the basis for studying the stability of rock engineering. To investigate the damage characteristics of rock containing non-parallel fissures, uniaxial compression tests and numerical simulations were conducted on sandstone specimens containing three non-parallel fissures inclined at 0°, 45° and 90° in this study. The characteristics of crack initiation and crack evolution of fissures with different inclinations were analyzed. A constitutive model for the discontinuous fractures of fissured sandstone was proposed. The results show that the fracture behaviors of fissured sandstone specimens are discontinuous. The stress–strain curves are non-smooth and can be divided into nonlinear crack closure stage, linear elastic stage, plastic stage and brittle failure stage, of which the plastic stage contains discontinuous stress drops. During the uniaxial compression test, the middle or ends of 0° fissures were the first to crack compared to 45° and 90° fissures. The end with small distance between 0° and 45° fissures cracked first, and the end with large distance cracked later. After the final failure, 0° fissures in all specimens were fractured, while 45° and 90° fissures were not necessarily fractured. Numerical simulation results show that the concentration of compressive stress at the tips of 0°, 45° and 90° fissures, as well as the concentration of tensile stress on both sides, decreased with the increase of the inclination angle. A constitutive model for the discontinuous fractures of fissured sandstone specimens was derived by combining the logistic model and damage mechanic theory. This model can well describe the discontinuous drops of stress and agrees well with the whole processes of the stress–strain curves of the fissured sandstone specimens.
KW  - Constitutive model
KW  - Damage mechanics theory
KW  - Discontinuous fractures
KW  - Uniaxial compression test
KW  - Non-parallel fissures
Y1  - 2024
U6  - https://doi.org/10.1016/j.tafmec.2024.104373
SN  - 0167-8442
VL  - 131
PB  - Elsevier
CY  - Amsterdam
ER  -