An SSTO as "God and Robert Heinlein intended".

[N_Molson]

Not at all. Basically, you just have to input the correct numbers in the configuration files. Just take any rocket that comes with the package and replace the numbers by your own, as a theoretical experiment.

[RGClark]

Quote:

Originally Posted by N_Molson

 Not at all. Basically, you just have to input the correct numbers in the configuration files. Just take any rocket that comes with the package and replace the numbers by your own, as a theoretical experiment.

Where are the configuration files and how do you execute the program?

Bob Clark

[Galactic Penguin SST]

Quote:

Originally Posted by RGClark

 Where are the configuration files and how do you execute the program?

Bob Clark

Download the Velcro Rockets add-on and read the documentation.

GPS

[T.Neo]

Velcro Rockets is a really fun and easy addon to play around with. There's nothing intimidating about it; it's all based on .cfg and .scn files, the functions are well described in the documentation and the values should make sense to anyone with a good idea of launch vehicle comparisons.

I've spent many an afternoon creating all sorts of interesting combinations (as well as all-new stages).

[RGClark]

Just saw this discussed on NasaSpaceFlight.com:

Untested Rocket Boosts SpaceX Revenue Nearly $1 Billion.
By Amy Svitak
Source: Aviation Week & Space Technology
September 17, 2012

Quote:

...Another change, she says, involves the rocket's nine Merlin 1D engines, which will be positioned in an octagonal configuration, rather than the “tic-tac-toe” placement on the current Falcon 9.
“You actually want the engines around the perimeter at the tank, otherwise you are carrying that load from those engines that are not on the skin,” she says. “You've got to carry them out to the skin, because that is the primary load path for the launch vehicle."
http://www.aviationweek.com/Article....495349.xml&p=2

See this thread on NasaSpaceflight for how this engine arrangement might look:

SpaceX Falcon 9 v1.1.
http://forum.nasaspaceflight.com/ind...6757#msg956757

This could have another advantage in that the octagonal arrangement of the engines makes possible the use of an aerospike in the center, if the center engine is removed.
This would give the first stage engines Merlin Vacuum type performance, raising the Isp from the ca. 311 s of the Merlin 1D to the ca. 340 s of the Merlin Vacuum.
This would result in a marked improvement in payload.


Bob Clark

[Urwumpe]

Yes, makes sense what is described there... you can actually already calculate this by using graphical computation methods.

The problem is, that such a placement is not without problems as well.

And no, I know I am the usual fun stopper here, but you won't get vacuum performance by installing an aerospike in the center of a ring of otherwise normal rocket engines. This is not how it works. even the theory of the "boat tail effect" is pretty doubtful today. And an Aerospike engine will also not operate at vacuum performance... it will simply be more effective than other engines outside the design pressure. That does not make it the magical solution for everything.

[T.Neo]

Interesting news. I wonder what the manugfacturing/assembly trade-off between this and the 'square' configuration is.

[Urwumpe]

Quote:

Originally Posted by T.Neo

 Interesting news. I wonder what the manugfacturing/assembly trade-off between this and the 'square' configuration is.

Well the main problem is quite easy to see there: you need a wider stage for fitting 8 engines into a geometry, that has them only on the circumference, compared to alternatives that have center engines or multiple concentric rings (topographically, rings and rectangles are the same... of course not geometrically).

Next, you still need some serious amount of thrust structure - while the construction works great if you have fixed engines thrusting forward, the situation looks differently when the engines gimbal. The radial forces of such a situation have again to be transported evenly on the tank walls, the thrust structure has to withstand it. you also can't just leave the bottom of the tank unsupported, it would simply drop out if the acceleration reaches a critical limit - the lightest way to prevent this is installing a supporting structure below it or go the egg way and have a dome that distributes the loads of the fuel to the side walls. But this would then mean that the tank gets longer and usually heavier, only in very few situations, such a construction works to your advantage (The German 206 series of submarines have such a inverted front bulkhead on their pressure hull)

Structural mechanics are for a very good reason a science of their own... the choices are literally endless and you can never run out of configurations to research, material combinations to test on old structures or simply have to include dynamic behavior better into your tests.

[RGClark]

Nice article here:

New Mexico space museum volunteers restoring DC-X for exhibit.
by TopSpacer on February 13, 2013 at 3:01 am
http://hobbyspace.com/Blog/?p=591#comment-7550

Bob Clark

[RGClark]

Orbital Science's Antares rocket is scheduled to launch this month:

Orbital's Antares Rocket Rolls Out to Pad in Preparation for First COTS Mission
By Mark Usciak

Quote:

Antares has a two-day window in which to launch Antares; it stretches from April 17-19. NASA hopes that initiatives like COTS and CRS will enable private companies to handle sending cargo (and perhaps one day crew) to destinations in low-Earth orbit. If these companies can do so affordably, then NASA would be able to conduct operations beyond the orbit of Earth for the first time in more than four decades.
http://www.americaspace.com/?p=33849

This is an important launch to give further support to NASA's more commercial approach to developing launchers.
Another reason this launch is important is because it uses the high efficiency Aerojet AJ-26 engine. This is derived from the Russian NK-33 engine. The NK-33 has long been a favorite of SSTO advocates because of its high Isp and high thrust/weight ratio at the same time.
Ed Kyle's page on the Antares estimates its first stage propellant load as 242 mT, and dry mass as 18.8 mT. The first stage is not weight optimized being based on old 1960's era Russian design.
However, SpaceX has shown by using various weight saving methods such aluminum-lithium alloy and common bulkhead design, that you can get a 20 to 1 mass ratio. Suppose we upgraded the first stage to get a 20 to 1 mass ratio. This would put its dry mass at 12 mT.
Kyle's page gives the AJ-26 a vacuum Isp of 331 s. The twin engines used on the first stage are given a vacuum thrust of 334,000 kgf at 100% and 370,000 kgf at 108%. Orbital Science's Antares brochure gives the vacuum thrust as 3,630 kN, which corresponds to 370,000 kgf, so I'll take this as the vacuum thrust:

Antares™
Medium-Class Launch Vehicle.
http://www.orbital.com/NewsInfo/Publ...s_Brochure.pdf

Now use Dr. John Schilling's rocket performance estimation program:

Launch Vehicle Performance Calculator.
http://www.silverbirdastronautics.com/LVperform.html

Input these numbers for the dry mass, propellant mass, Isp and thrust. Select "No" for the "Restartable Upper Stage?" option. Select Cape Canaveral as the launch site, which will provide for better payload than from Wallops. Input 28.5 degrees as the inclination of the orbit to match the latitude of a launch from Cape Canaveral. Then I get about 3,400 kg to LEO:

====================================
Mission Performance:
Launch Vehicle: User-Defined Launch Vehicle
Launch Site: Cape Canaveral / KSC
Destination Orbit: 185 x 185 km, 28 deg
Estimated Payload: 3399 kg
95% Confidence Interval: 722 - 6633 kg
====================================


Bob Clark