Feeds:
Posts
Comments

Archive for the ‘Suborbital’ Category

Watch in high res at youtube. White Knight Two doesn’t look so large span after all. Spaceship Two is pretty wide with its outset elevons and the WK2 outer wings need to have the engines so there’s not much wing outside with the single purpose of lifting (or stopping the tip vortex). It seems both planes are really light too. Carbon fiber throughout. SS2:s wheels are really tiny. They have gone for minimum dry mass. The landing speed doesn’t seem huge even with its low aspect ratio. Maybe the size misleads. The landing is very smooth.

Of course the couple climbs out very fast even with gear out since SS2:s tank is empty and it doesn’t have the solid fuel onboard either.

I’m reminded of the lifting body research of the sixties. Who says we aren’t experiencing the golden age of aerospace right now? There’s happening interesting stuff left and right now, most of it in the more modest programs.

Advertisements

Read Full Post »

Inspired by Michel Van (not Scott Lowther as mentioned earlier) at Secret Projects, who ran into the Gemini inflatable Rogallo wing test videos that are now available (not embeddable so linked only). There are parafoil systems for airdropping stuff, though they don’t seem to be doing flares or line pulls to soften the impact:

And if somebody says parafoils are not maneuverable, I give you a Russian self built RC parafoil:

Speaking of rocketry, a member from the local hybrid group said they have found out the probable cause of roll control problems: the forward fins that were put on the rocket for roll control cause huge vortices when deflected, so that they effect the main fins far aft and the effect might be the opposite from intended.

Read Full Post »

In a patent by the famous Barnaby Wainfan. EDIT: corrected the link. This patent was filed in 2006 and granted in 2008.

Enter, turn, boost, glide

Read Full Post »

Well, scaling seems to be my pet issue. I recently wrote something not entirely well reasoned in a comment at Paul Breed’s. (For some reason Chrome complains about blogrolling.com malware there so continue if you’re sure you’re safe.)
So let’s make it better. (A word of caution though, I’m quite sleep deprived now.)
For those who like to jump into conclusions, it’s going to be like this all over again.

Assume a pressure fed rocket first stage has a certain propellant chemistry, tank and thus chamber pressure and must operate in the atmosphere, hence has a certain exit pressure (0.1 MPa or 1 bar or 15 psi is the optimal). Then it has certain thrust per nozzle area.

Now, the rocket needs thrust to lift off. If we assume a constantly scalable shape, its mass will be base area times length times density.

Since the maximum fittable nozzle exit plane also depends on the base area, we find that for a certain area, the rocket can only have so much mass – or that the rocket has a maximum density times length parameter. If we assume the propellants have been picked early on, density is set and the rocket only has a height constraint.  Each pressure and propellant chemistry basically has a “characteristic length” that can’t be exceeded. Otherwise it can’t lift off.

The higher the exhaust velocity, the smaller the nozzle, so raising chamber pressure reduces the needed nozzle size per thrust and the rocket can be lengthened.

For small rockets, I’d hunch that they have little length and thus they don’t really have to worry about this. They can be as thin (and thus long) as practical, to try to avoid drag losses.

For upper stages, the thrust to weight needed is less and the weight even less so it’s even less of a problem – except that the expansion ratios can be huge since there’s no back pressure anymore. Still, with small rockets, pretty huge expansions might be possible without having much problems because the second stage is very small (=also short) anyway and thus there’s little mass per nozzle exit plane area.

On really tall rockets like Saturn V, the thrust per base area has to be huge, hence it had to have those base extensions for the corner engines (note how the N-1 had a conical shape with a wider base, the engines had a bit higher pressure but the upper stages were kerosene – these cancel out a bit but the base of the rocket had some empty space) . Similarly with STS, putting so much thurst on the tiny orbiter’s tail required high chamber pressures and some tail shaping

I don’t have any numbers handy, but if we assume a 10 m tall 1000 kg/m^3 density (water) rocket, then it has 10,000 kg per m^2 or the thrust required for a 20 m/s² acceleration is 200,000 N/m^2. This is easily achievable. With an exhaust velocity of 2000 m/s, the mass flow needs to be 100 kg/(s*m²) to produce that thrust. Again with the exhaust velocity that mass flow means a density of 0.05 kg/m^3. Air’s density is 1.2 kg/m^3 at 300 K, so that’s 20 times less dense which means hotter, the density is like hot air at 6000 K. Though the molecules might be mostly lighter OH instead of N2 and O2, making that rocket exhaust at 3000 K for the density. Rocket exhaust isn’t that hot – it’s cooler and denser and thus more thrust per unit area.

For a second stage we can look at the pressure fed AJ-10 from Delta 2: 1.7 meters diameter (certainly constrained), 40 kN of thrust. For a T/W of 1, density of 1000 kg/m^3, we get 4 tonnes and 1.7 meters of depth. Quite a stubby stage with a roughly spherical tank! Isp is 321 s. The real Delta II second stage weighs 7 tons and the payload is some too, but reusable rockets won’t have such high performance first stages (nevermind solids!), so they might need more T/W.

Oh, BTW, I assume three stages to orbit for pressure feds though I haven’t looked it that closely.  Mass ratios and ISP:s I’ve only hunched.

Read Full Post »

EDIT2 Video is online now. END EDIT


(I haven’t worked with the rocket, I just know the people who did this!)

Read Full Post »

Altitude was 2222 m. Apparently the backup timer shot the drag chute out while the rocket was still ascending. The team said they have video and will upload it later, if asked nicely enough. 🙂
Meanwhile, some launch photos.
You can see the small roll control vanes in the forward fuselage.

Read Full Post »

A Finnish largish amateur hybrid rocket project, Iso-Haisu (Large Stinky or Big Skunk, the successor of the smaller Haisunäätä, Skunk, the first Finnish hybrid) was flown today at a military artillery range. Reports say it disappeared into the clouds but it has not yet been located. The flight computer logger was onboard so the altitude is unverified. And no onboard video / pictures yet either!

The rocket radioed furiously after landing but failed to get found. It apparently landed about a kilometer from the launch site when the GPS data was deciphered.

It’s a heavy rocket with considerable overbuilding and lots of electronics. Better not try to reach all the goals at the same time.
Hope it gets found tomorrow!

Read Full Post »

Older Posts »