Lenticular Lifting Body

Vi allego l’executive summary di un progetto di veivolo privato per turismo spaziale in orbita che prevede l’utilizzo del futuro Falcon V. Il progetto è realizzato dalla Grinning Torch Enterprises in collaborazione con alcune università USA. Ma cio’ che ha attratto la mia attenzione è l’utilizzo di un “lenticular lifting body”. Lo studio sembra essere veramente interessante…
A chi ne fa richiesta posso spedire lo studio completo via e-mail.

“In this study, Grinning Torch Enterprises sought to develop a space tourism vehicle concept and model a space tourism business case which can break even by the end of five years of flight operations, realize a minimum Internal Rate of Return (IRR) of 30% on the business through the end of ten years of flight operations, and stay within a maximum debt exposure of $250M (FY05). To begin, Grinning Torch established a design space of alternative concepts and executed an exhaustive downselection process utilizing a zero-order analysis and Systems Engineering techniques to determine that a lenticular lifting body is the most appropriate vehicle for the given mission. Grinning Torch also determined that developing its own launch vehicle within the debt exposure constraint would be impossible and decided to launch the crew module
on SpaceX’s future Falcon V launch vehicle.
Although unconventional, a significant amount of research done on the lenticular shaped lifting body in the 1960’s led Grinning Torch to believe that the vehicle was feasible for entry.
In this design, deployable flaps remain stowed as the vehicle enters at an 80o angle of attack, creating a near ballistic entry with a relatively large nose radius to minimize the effects of aeroheating.
Wind tunnel tests have confirmed the stability of the craft through this phase of entry.
After passing peak deceleration and heating, the flaps deploy and the vehicle performs a lifting entry for the remainder of the trajectory, ultimately landing on a runway.
Although placing a lifting body on top of a launch vehicle can lead to problems involving aerodynamic forces, a significant number of studies using this configuration in addition to precautions taken in the ascent trajectory cause Grinning Torch to believe that this configuration is feasible. After orbit insertion, passengers are free to float about the cabin and look at the Earth below. The nominal mission includes roughly three orbits for a period of almost 5 hours in space. The vehicle both takes off from and lands at Kennedy Space Center.
With space travel being an inherently dangerous activity, as many precautions as possible were taken to ensure the safety of the passengers and crew. The Falcon V has some safety features such as a hold-before-release system upon launch and engine out capabilities. In addition, multiple abort scenarios were analyzed in the case of a benign launch vehicle failure during ascent. The crew vehicle is also fitted with an early ascent abort system which would propel it away from the launch vehicle in the case of a failure on the launch pad or in the first 50 seconds of ascent.
Costing of the vehicle and operations was performed using costing tools such as TRANSCOST. These costs together with market predictions from the economics tool Launch Market for Normal People (LMNoP) allowed Grinning Torch to assess different possible scenarios to determine viability of each. For the nominal business case, Grinning Torch
Enterprises meets the constraints with an IRR of 51% through the end of 10 years of flight operations and a maximum debt exposure of $192M (FY05).”

Interessante, anche se non si tratta di una idea nuova (come del resto lo stesso autore dell’articolo riporta).
La configurazione lenticolare era una tra le sei iniziali prese in consiederazione per il progetto Apollo. Fu scartata, perché presentava una serie di problemi tecnici di difficile soluzione, dall’interfaccia con la torre di salvataggio alla distribuzione degli ambienti interni.
Benché favorita da alcuni centri NASA la configurazione lenticolare fu scartata nel 1961 in favore della capsula semibalistica.

Per chi volesse saperne di più l’immancabile Mark Wade ha scritto un breve articolo sulla sua Enciclopedia Astronautica:

http://www.friends-partners.org/partners/mwade/craft/apocular.htm

In ogni caso ritengo improbabile, come riportato nell’articolo, che un corpo portante lenticolare sia in grado di effettuare un atterraggio su pista come un normale velivolo, sembra più fattibile una discesa con un parasail ed un atterraggio a punto fisso (come le capsule).