An-225 as a launch vehicle

[Lukaszenko]

Did anybody else see this article? Apparently they want to build many An-225s and use them as launch vehicles. 

Kind of cool. I guess. But, did they get their math REALLY wrong? "90% of the energy of the launch vehicle is spent getting up to an altitude of 10km"? Even my friend who knows NOTHING about spaceflight was dubious about this, if for no other reason than that satellites fly MUCH higher than 10 km (disregarding any sideways velocity). He's actually the one that asked about this. Anyway, it's not him that's going to throw down billions to make this happen, so he didn't really care that much.

And what? They wanted to use the An-225 to launch a fully loaded Buran & Energia from this plane's back? Eh? 

I know it can lift a lot, but 2.5 million kg is a bit more than a lot.

Anyway, normally I wouldn't care about stuff like this, but this is a legitimate article about a legitimate thing from a legitimate source. Really made me go like this  

http://www.bbc.com/future/story/20170503-the-worlds-biggest-plane-may-have-a-new-mission

 

Edited May 7, 2017 by Lukaszenko

[magnemoe]

Same issue as with the stratolauncher, upside is that the 225 might haul an heavier cargo,
Wonder if they will do an top launch or cargo hold drop, latest put rocket on an wagon who rolls out of the plane and then fire it up, 
US air force has tested it and it works. 
safer than top launch 

And benefit of air launch is mostly that you can use vacum optimized engine for first stage and you can fly south to get an better inclination. 

[Wjolcz]

A MAKS-like shuttle would be cool.

[SargeRho]

I was about to say, wasn't the MAKS supposed to launch from an An-225?

[wumpus]

Have you played KSP at all?  [Even the demo version will teach you this, just ignore the lessons of spaceplanes outside of realism overhaul (they basically break the game thanks to the toy size of Kerbin)].

Most of what they say is likely technically true, but pointless.  Getting into orbit is an exercise in speed, not altitude.  A rocket that burns out 90% of its fuel in the first 10km is burning the fuel in a goal to get that speed, not to get to 10k.  The two other reasons it could happen:

1.  It is typically cheaper to extend the fuel tanks than to make a more powerful engine.  This means many rockets will leave the pad with a TWR of 1.1 to 1.2, meaning the rocket is hideously inefficient [in terms of fuel.  It is still a smart design] when it launches.  About the only efficient way to add power (and later throttle down if applicable) is to use solid rocket motors (typically strapped to the sides).
2.  Extra small rockets suffer aero losses disproportionate to larger rockets (effectively aero efficiency scales with length of a booster).  For any rocket that can be carried with by an airplane (even the big boys like An-255 and Stratolaunch) expect aero significant losses compared to something the size of a Soyuz.

Mostly, this all depends on how easy it is to modify the An-255.  Orbital got its start this way (it started with a B-52 which was designed to drop bombs and they could use some of NASA's designs for dropping the X-15).  Statolaunch is effectively dead (it costs billions to design a modern jetliner, don't expect Stratolaunch to be much cheaper) and there's no real way to recoup the costs.

[DDE]

BBC is being stupid again, and I'm not sure Yuzhnoi can get anywhere close to building a MAKS replica.

But otherwise it's a well-worked concept.

[K^2]

8 hours ago, wumpus said:

Most of what they say is likely technically true, but pointless.  Getting into orbit is an exercise in speed, not altitude.  A rocket that burns out 90% of its fuel in the first 10km is burning the fuel in a goal to get that speed, not to get to 10k.

You aren't actually getting much speed in the first 10k. Most of the thrust is spent fighting atmo and gravity to get to thinner air. 10km up, a rocket is going to be through about 1.5km/s of its 9km/s delta-V to orbit. That's going to be between a third and half of its fuel, depending on I_SP. So 90% thing is definitely crap, but because it's simply wrong, not on technicalities.

[YNM]

7 hours ago, DDE said:

BBC is being stupid again, and I'm not sure Yuzhnoi can get anywhere close to building a MAKS replica.

It's partially their fault (mind that most BBC Future things are usually somewhat wishful thinking). But it has something to do with the chinese trying to resurrect An-225 production. I mean, alright they probably really want the cargo capacity, but who knows what the chinese have in the back of their mind ? Maybe they want to have a go on the whole Shuttle-design as well...

[Kryten]

There is a Chinese air-launched vehicle either in advanced studies or in development (sources differ), but it's not very big and meant to be shoved out the back of a domestic Y-20 transport.

Edited May 8, 2017 by Kryten