Analytic Considerations for Lifting Ascent Launch Vehicle Trajectories

[martinbayer]

This post represents the results of an analytical approach I developed in my university days for the performance evaluation of RLVs that utilize aerodynamic lift during ascent. The concrete motivation was the fact that in a course on ramjet design I was told by the docent that for first order performance assessments of ramjets the classical rocket equation could be used. Since that equation is however strictly valid only for a constant effective exhaust velocity and in the absence of external forces, such as atmospheric drag or gravity, while winged launch vehicles with aerodynamic ascent and especially air breathing propulsion may experience significant aerodynamic forces and large variations in the effective exhaust velocity, I decided to try to find if there was a better way - turns out there is. Attached are a briefing that provides an overview of the underlying theory and some concrete comparative results as well as the listing of the associated software that I wrote back in the day in C. More details and background information can be found in a paper called "Analytic performance considerations for lifting ascent trajectories of winged launch vehicles" by yours truly, which was published in Acta Astronautica 54 (2004) 713 – 721. I'll gladly answer any questions as far as my memory serves, and please feel free to recreate/adapt the software.

 

[martinbayer]

This post represents the results of an analytical approach I developed in my university days for the performance evaluation of RLVs that utilize aerodynamic lift during ascent. The concrete motivation was the fact that in a course on ramjet design I was told by the docent that for first order performance assessments of ramjets the classical rocket equation could be used. Since that equation is however strictly valid only for a constant effective exhaust velocity and in the absence of external forces, such as atmospheric drag or gravity, while winged launch vehicles with aerodynamic ascent and especially air breathing propulsion may experience significant aerodynamic forces and large variations in the effective exhaust velocity, I decided to try to find if there was a better way - turns out there is. Attached are a briefing that provides an overview of the underlying theory and some concrete comparative results as well as the listing of the associated software that I wrote back in the day in C. More details and background information can be found in a paper called "Analytic performance considerations for lifting ascent trajectories of winged launch vehicles" by yours truly, which was published in Acta Astronautica 54 (2004) 713 – 721. I'll gladly answer any questions as far as my memory serves, and please feel free to recreate/adapt the software.

In case there is interest in recreating the software, which is freeware, attached is a Word transcript of the code provided as a PDF above that includes English translations for the German terminology used in the original. The actual software listing is the white section, while the yellow section is an input example, and the green section is a corresponding output example. I'll gladly provide any expertise, support, and information I can to restore full functionality, if desired. Please let me know if you have any questions or would like further clarification.

 

[Nicknick]

Guess this came out of your Doktor/Diplom thesis?

Intresting, despite I haven't gone through all the math behind it, at least I understand which proplems are you facing when developing such vehicles.

Unfortunately, this knowledge might end up in the wrong hands, but this is true for all aviation stuff...

 

[martinbayer]

Gues this came out of your Doktor/Diplom thesis?

Actually no, although my aerospace engineering diploma thesis was on the optimization of return trajectories of airbreathing winged booster stages of HTHL TSTO RLVs a la Saenger ll by modifying an existing numerical simulation program, I developed this approach during my time at university purely out of personal interest/curiosity.