Author Topic: DynaSoar spaceplane (Read 12103 times)

Archibald · « **Reply #45 on:** April 23, 2006, 10:56:10 pm »

I know this concept too... it was studied by USAF in 1994. Main problems are flight refuelling is not easy on this case (it's a rocket, not a fighter so the mass of Kerosene to trasnfer is huge, causing stability problems during the refuelling). Other problem is even if the plane take off with the fuel tank empty, it is still too heavy to reach orbit by itself and you need an expendable upper stage to send the payload in orbit.
The concept is nevertheless interesting because it take off from an airport (much more easy than a launch pad).
Other interesting concept is MAKS, but the spaceplane has an expendable tank. Apparently the blackstar is the same concept but a revolutionnary fuel (?) eliminate the external, expendable fuel tank (the mothership has also a superior top speed, the engine are Aerospikes)

Archibald · « **Reply #46 on:** April 25, 2006, 02:46:47 am »

Concerning single stages to orbit, the way is very difficult
- airbreathing engines such a Turbofans or Ramjets gave a top speed of mach6 before the light of the Rocket engine. Comparing to Mach25 orbital speed, this is too weak and as a consequence rocket fuel consuption is still too much (even at mach 6, you need external tanks to reach orbit).
Aparently the best option would be starting the rocket engine after reaching mach 10. Of course, you need another airbreathing engine to accelerate between mach6 and mach10... this is the scramjet. Problems with it are so enormous that 40 years have passed between the concept phase in the 60's and the first succesfull flight in the 90's-2000's.
Other solution would pure rocket from take off to orbit. In this case you have huge mass penalties, as Tsikolvski demonstrated 100 years ago! 92% of the take off mass must be... propellants! This explain quite simply why the X-33 failed...
Variant of the concept include the concept describe by madoc (in smaller variants). The main problem with that is weight augmentation.
On the paper, the concept seems viable. the problem is in every spaceship or plane design and building phase, there's weight problems. for example, the A380 must weight 540 tons at the beginning, and ended near 560/570. This 2% augmentation can be catastrophic for the concept Madoc described... and it is unavoidable!

GTX · « **Reply #47 on:** April 25, 2006, 03:26:52 pm »

Hi folks,

This discussion reminded me of the RASCAL (Responsive Access, Small Cargo, Affordable Launch) program/concepts. Here is some information. I also have a full presentation prepared by JPL (I think) somewhere - if I can find it, it is available to anyone interested.

Regards,

Greg

Archibald · « **Reply #48 on:** April 26, 2006, 06:06:35 am »

Interesting concept. Semi reusable with exependable upper stage... hypersonic airbreathing first stage is not easy to make, but DARPA represent one of the best laboratories in the world... and such stage could be very useful later

Archibald · « **Reply #49 on:** April 28, 2006, 05:31:36 am »

Lets come back to Dyna Soar...
After 15 years of successfull flight with USAF, NASA and CIA, the DynaSoar I was free for export markets. After the outbreak of WWIII in 1983, many countries needed high performances recon system to overfly USSR.

The US governement wanted to sell the DynaSoar spaceplane to its allies but a big problem quickly appeared. The DynaSoar launcher, Titan V was unafordable for exports markets, because of its costs, launch pad, and assembly line. As a consequence, Boeing proposed a much simpler way of launching the space plane.

The idea was using a 747 and an expendable upper stage to push the small shuttle in orbit. Boeing first thought was using the Saturn V S-IVB but it was impossible to put it piggy back on the 747 because of its big diameter. More, its J-2 engines were using hydrogen, a dangerous fuel to handle.
As a consequence, Boeing changed its plans and created a cheap expendable stage. They used the H-1 engine of the Saturn I rocket; it had the same thrust as the J-2 but used Kerosen, like its 747 carrier!
More, Boeing ingeneers had a brilliant idea : they adapted the diameter of the stage to the 747 cargo bay. This idea allowed the foreign users of the system to use the 747 not only as launcher, but also as ferrying aircraft!
The 747 launcher was basically similar to the 747-200F, but part of the fuel (and range) was cut to boost the payload at take off. Payload was now 160 tons at take off, range was 4500km only (but sufficient)
The system was quite cheap because the 747, H-1 and DynaSoar were well-known technologies... so DynaSoar started to wear foreign markings (stay tunned!)