segunda-feira, 15 de dezembro de 2014

Resistance, When Things Get Hot

Hello reader!

Here is an interesting article published in the DLR Magazine (sept. 2014 - English Edition) highlighting to the SHEFEX III Project, which was recently initiated by the German DLR.

Duda Falcão

RE-ENTRY TECHNOLOGY

Resistance, When Things Get Hot

Only those who master all three phases of a space mission attain full
competence in space. In addition to the launch into space and the
operational phase in orbit, there is also the transportation back to Earth
– and with this comes the necessary re-entry technology. The development,
construction and flight testing of this technology are conducted at DLR under
the name SHEFEX – Sharp Edge Flight EXperiment. Currently, DLR researchers
are preparing for the third phase of the SHEFEX flight test programme. Making
such a complex flight mission feasible at reasonable cost is unique in Europe.

The autonomous spacecraft SHEFEX III demonstrates
the effects of re-entry into Earth’s atmosphere

By Hendrik Weihs
DLR Magazine
Sept. 2014

Schematic structure of SHEFEX III and the onboard systems
for flight control and instrumentation.

The technological challenge associated with atmospheric re-entry and the subsequent flight until landing is the rapidly changing aerodynamic conditions between the first noticeable gas effects – at an altitude of about 100 kilometres and a speed of nearly 28,000 kilometres per hour – and that of the landing, at a speed of only a few hundred kilometres per hour (or significantly lower when parachutes are used). The speed and air density within this range are constantly changing. The key to mastering re-entry lies in understanding and predicting the aerodynamic conditions over the entire range of speeds and optimising structures to withstand the thermal and mechanical loads.

For capsule-like ballistic space vehicles this is rather straightforward. However, a spacecraft that exhibits a high degree of flexibility and controllability to approach a specific landing site in the final phase of the flight must have two properties: a high aerodynamic quality in the hypersonic range (speeds well above 1000 kilometres per hour) and an intelligent flight control system. Using the measurement data acquired during flight, the SHEFEX programme provides the most important answers for improving and verifying simulations and predictions.

With SHEFEX I it was possible to reach Mach 6, six times the speed of sound. This was extended to Mach 11 with SHEFEX II, which also provided fundamental experience concerning the complex effects associated with aerodynamic flight control. The next major step is being taken with the third mission, SHEFEX III, which has recently been initiated. In contrast to the previous two missions that cruised through all altitude ranges with a nearly constant velocity, the autonomous space vehicle SHEFEX III will demonstrate a continuous deceleration from the beginning of the re-entry at an altitude of 100 kilometres (at around Mach 17) until the end of the experiment window at an altitude of 20 kilometres (at Mach 2).

Thus, the flight conditions will come very close to that of a real re-entry from orbit and will cover the critical atmospheric effects. Here, the sharp-edged shape of the spacecraft offers lower drag and significant lift, which in conjunction with a complex control system that features flaps, a sliding weight and reaction nozzles, enables flight along a predetermined trajectory. From a structural point of view, SHEFEX III retains the faceted and thus more cost-effective form of thermal protection, as well as the sharp leading edge with special ceramics and cooling techniques.

The SHEFEX programme encompasses all the relevant disciplines and DLR institutes. Airbus Defence and Space has been brought in as industry partner for the flight control systems for SHEFEX III.

PROJECT INFORMATION

As part of the SHEFEX flight test programme, the German Aerospace Center, DLR, is developing technologies for spacecraft atmospheric re-entry. The research includes the development of basic technologies, such as material systems and structural concepts, numerical design tools, aero-thermodynamic design of the vehicle, as well as the development of appropriate flight guidance and control systems.

Author: Hendrik Weihs has worked at the DLR Institute of Structures and Design in Stuttgart for 27 years. He is responsible for the SHEFEX project.


Fonte: DLR Magazine - No. 142/143 - pages 22 and 23 - September 2014

Comentário: Bom leitor como se pode notar neste pequeno artigo o projeto do SHEFEX III foi iniciado recentemente (talvez em 2014) e não logo após o lançamento do SHEFEX II em junho de 2012 como imaginávamos. Este fato deve ser preponderante para mais um atraso no Projeto VLM-1 (se é que podemos acreditar neste projeto) talvez jogando-o para 2017, 2018 ou até mesmo 2019, caso se venha levar em conta o período de tempo gasto em desenvolvimento pelo DLR nas fases anteriores do programa (SHEFEX I e II). Entretanto, fiquei sabendo que um acordo que envolve o DLR, a AEB, o IAE e talvez o SSC (o que confirmaria a matéria da jornalista Virgínia Silveira do Jornal Valor Econômico postada aqui no blog dias atrás – veja aqui)  foi assinado bem recentemente no âmbito do projeto do VLM-1, e segundo minha fonte (sempre otimista) existe a crença de que agora o projeto vai andar, coisa que eu sinceramente não acredito, pelo menos não dentro do cronograma que deve ter sido acertado na assinatura deste acordo. É preciso entender que mesmo que a burocracia tenha diminuído neste caso específico como sinalizado pela minha fonte, à má vontade política em relação ao PEB só faz aumentar ano após ano e leitor, programa espacial se faz com dinheiro e não com promessas. Em resumo, o fato de a burocracia ter diminuído por conta do modelo agora adotado não é garantia nenhuma de que o governo irá liberar recursos e muito menos que irá fazê-lo dentro do cronograma previsto. Além do mais vale lembrar que o Brasil é conhecido por não cumprir seus acordos internacionais dentro do prazo, especialmente aqueles ligados a área espacial, e com a “Ogra” no poder então... Portanto leitor, não leve essa notícia como tão positiva assim, pois a mesma só gera ainda mais incertezas. Sinceramente espero estar enganado como estava em relação ao CBERS-4, mas...

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