Transient thermal analysis during the ascent phase of a balloon-borne payload. Comparison with SUNRISE test flight measurements

The thermal design of stratospheric balloon payloads usually focuses on the cruise phase of the missions, that is, the floating altitude conditions. The ascent phase usually takes between 2 and 4 h, a very small period compared to the duration of the whole mission, which can last up to 4 weeks. However, during this phase payloads are subjected to very harsh conditions due mainly to the convective cooling that occurs as the balloon passes through the cold atmosphere, with minimum temperatures in the tropopause. The aim of this work is to study the thermal behaviour of a payload carried by a long duration balloon during the ascent phase. Its temperature has been calculated as a function of the altitude from sea level to floating conditions. To perform this analysis it has been assumed that the thermal interactions (convection and radiation) depend on the altitude, on the environmental conditions (which in turn depend also on the altitude) and on the temperature of the system itself. The results have been compared with the measurements taken during the SUNRISE test flight, launched in October 2007 by CSBF from Fort Sumner (New Mexico).

An engineering modification of the blade element momentum equation for vertical descent : an autoration case study

An engineering modification of blade element/momentum theory is applied to describe the vertical autorotation of helicopter rotors. A full non-linear aerodynamic model is considered for the airfoils, taking into account the dependence of lift and drag coefficients on both the angle of attack and the Reynolds number. The proposed model, which has been validated in previous work, has allowed the identification of different autorotation modes, which depend on the descent velocity and the twist of the rotor blades. These modes present different radial distributions of driven and driving blade regions, as well as different radial upwash/downwash patterns. The number of blade sections with zero tangential force, the existence of a downwash region in the rotor disk, the stability of the autorotation state, and the overall rotor autorotation efficiency, are all analyzed in terms of the flight velocity and the characteristics of the rotor. It is shown that, in vertical autorotation, larger blade twist leads to smaller values of descent velocity for a given thrust generated by the rotor in the autorotational state.

Tissue engineering of cartilage in space

Tissue engineering of cartilage, i.e., the in vitro cultivation of cartilage cells on synthetic polymer scaffolds, was studied on the Mir Space Station and on Earth. Specifically, three-dimensional cell-polymer constructs consisting of bovine articular chondrocytes and polyglycolic acid scaffolds were grown in rotating bioreactors, first for 3 months on Earth and then for an additional 4 months on either Mir (10−4–10−6 g) or Earth (1 g). This mission provided a unique opportunity to study the feasibility of long-term cell culture flight experiments and to assess the effects of spaceflight on the growth and function of a model musculoskeletal tissue. Both environments yielded cartilaginous constructs, each weighing between 0.3 and 0.4 g and consisting of viable, differentiated cells that synthesized proteoglycan and type II collagen. Compared with the Earth group, Mir-grown constructs were more spherical, smaller, and mechanically inferior. The same bioreactor system can be used for a variety of controlled microgravity studies of cartilage and other tissues. These results may have implications for human spaceflight, e.g., a Mars mission, and clinical medicine, e.g., improved understanding of the effects of pseudo-weightlessness in prolonged immobilization, hydrotherapy, and intrauterine development.

Rocket science and missile engineering.

Mode of access: Internet.

A similitude for nonequilibrium phenomena in hypersonic flight,

"Part I of the present paper was supported by the Arnold Engineering Development Center under Contract no. AF-40-(601)-928. Part II is a part of project DEFENDER sponsored by the Advanced Research Projects Agency, Department of Defense, under Contract no. DA-30-069-ORD-3443."