Will StratoLaunch Fly?

[fredinno]

Will Stratolaunch actually get things into orbit, and will it be sustainable? Really, the rocket is entering a pretty empty launch market (5T to LEO) with not very many payloads, and lacks a rocket (not even Orbital could satisfy them).

[Kryten]

We can't really give a good guess until they reveal the new rocket design and who's building it, but having gone through two (possibly three) designs already doesn't bode well for their general program management. I give it 50/50 right now.

[Nibb31]

I think that both Allen and Branson have a lot in common. Unlike Musk, they are business people, not geeks. They hire people who are experts, but they are not experts themselves, and the people they hired were probably more influenced by the fat pay checks that by the laws of physics when they gave their advice.

In the end, they both definitely underestimated the harsh difficulty of spaceflight, and wildy overestimated the benefits of air launch. Anyone in the industry knows that it's a dead end and that the drawbacks outweigh any benefits by an order of magnitude.

After 5 years of development, Stratolaunch still doesn't have a rocket, nor does it have a partnership deal to obtain one. I say it's dead in the water. The carrier plane might fly a couple of times, but then it'll end up in a hangar like Hughes' Spruce Goose.

Edited October 16, 2015 by Nibb31

[PB666]

http://www.nytimes.com/2016/06/20/science/stratolaunchs-gargantuan-flying-launchpad-edges-toward-the-skies.html?partner=IFTTT&_r=2

 

[YNM]

If Burt Rutan still involved and the money is in somewhere then it will. You know any aircraft Burt Rutan made flies and flies very, very well.

[Robotengineer]

I haven't seen this before. It seems rather ridiculous. There is really no need to launch rockets from an airplane. 

[Nibb31]

1 hour ago, Robotengineer said:

I haven't seen this before.

Where were you the last 5 years ?

[Kryten]

On 10/16/2015 at 1:13 AM, Kryten said:

We can't really give a good guess until they reveal the new rocket design and who's building it, but having gone through two (possibly three) designs already doesn't bode well for their general program management. I give it 50/50 right now.

We're over six months after this point, and the only thing that's really changed is it's become clear they hadn't actually selected a new LV design. We don't even have any LV designers on record as saying they would like to partner with them. 

[wumpus]

2 hours ago, Nibb31 said:

Where were you the last 5 years ?

Wiki claims that Pegasus hasn't flown since 2013 (two flights since 2008, with single flights in 2016 and 2017 scheduled).  It doesn't look all that good for air-launched rockets.

This is one of those things that "it works in KSP" (assuming you have the flight manager mod) but not so much in real life.  Although I really think the X-43 has potential (which, unlike the stratolaunch, should supply meaningful delta-v).

I'm guessing this roc is laying an egg.

[Robotengineer]

7 hours ago, Nibb31 said:

Where were you the last 5 years ?

I only started really paying attention to commercial space development 2-3 years ago, around the time I started playing KSP. Before that I was younger and wasn't as interested in current events in the commercial space sector. 

[magnemoe]

16 hours ago, wumpus said:

Wiki claims that Pegasus hasn't flown since 2013 (two flights since 2008, with single flights in 2016 and 2017 scheduled).  It doesn't look all that good for air-launched rockets.

This is one of those things that "it works in KSP" (assuming you have the flight manager mod) but not so much in real life.  Although I really think the X-43 has potential (which, unlike the stratolaunch, should supply meaningful delta-v).

I'm guessing this roc is laying an egg.

Think the pegasus is to small to put most useful satellites in specified polar orbits, if you just want an small satellite to LEO its cheaper to hitch a ride. 

[DDE]

Uhm, the original Pegasus is a total wimp, we can go bigger if needed with merely off-the-shelf equipment.

 

[StevieC]

By air-launching the vehicle, you effectively have replaced the first-stage booster with a reusable, manned, air-breathing first-stage that lifts of and lands horizontally. If you can design the craft to use air-breathing engines for the stages that operate whilst still within the atmosphere, using either ramjets or scramjets or a combination of both, then those stages don't require any LOX, just the fuel, be it LH₂, kerosene, liquid methane, or what-have-you. This, plus use of wings to provide aerodynamic lift, could reduce the amount of energy expenditure required both to overcome gravity and to overcome aerodynamic drag. This use of air-breathing engines and aerodynamic lift would allow a launch-system to exploit the atmosphere as a propulsive aid, rather than forcing it to overcome the atmosphere as an obstacle.

[wumpus]

24 minutes ago, StevieC said:

By air-launching the vehicle, you effectively have replaced the first-stage booster with a reusable, manned, air-breathing first-stage that lifts of and lands horizontally.

For values of first stage boosters with near-zero delta-v.  And significant cost.

How much would it really cost to build a launch pad in Ecuador anyway?  Because that would do everything an airlaunch does.

Edited June 21, 2016 by wumpus
Ecuador argument

[PB666]

14 minutes ago, wumpus said:

For values of first stage boosters with near-zero delta-v.  And significant cost.

How much would it really cost to build a launch pad in Ecuador anyway?  Because that would do everything an airlaunch does.

At the equator.

[StevieC]

17 minutes ago, wumpus said:

How much would it really cost to build a launch pad in Ecuador anyway?

You would not want it there because then every launch would be overflying several hundred kilometers of landmass, much of which is populated. The best place in the Western hemisphere to place an equatorial launch-site would be at Macapá, on the coast of Brazil.

[Nibb31]

47 minutes ago, StevieC said:

By air-launching the vehicle, you effectively have replaced the first-stage booster with a reusable, manned, air-breathing first-stage that lifts of and lands horizontally. 

A first stage that only provides 250m/s, negligeable altitude, and wastes immobilization money as a hangar queen.

[StevieC]

Depending on the type of aircraft, it could provide significantly more than that. In the early 1960s, North American Aviation, builders of both the mach 3 XB-70 Valkyrie and the mach 6 X-15, proposed carrying a modified X-15 (one with a delta-wing and possibly a ramjet engine to propel it while still in the atmosphere) to 80,000 feet altitude atop the rear-fuselage of an XB-70, to bring the vehicle to supersonic speed before releasing it from its launch-plane. Unfortunately, only one of the two XB-70s would have been suitable for that mission, and that one was the plane that suffered damage from a collision with an F-104 in 1966, which caused the Valkyrie to crash in the desert near Barstow, California.

At 80,000 feet altitude, most of the thicker air is below you, but if you're traveling at Mach 2 or Mach 3, forward speed still collects enough oxygen for air-breathing engines to be a viable means of propulsion, and some air-breathing engine designs have the potential to offer enough delta-V to lift one's apoapsis to a respectably high orbital radius.

Edited June 21, 2016 by StevieC

[Nibb31]

8 hours ago, StevieC said:

At 80,000 feet altitude, most of the thicker air is below you, but if you're traveling at Mach 2 or Mach 3, forward speed still collects enough oxygen for air-breathing engines to be a viable means of propulsion, and some air-breathing engine designs have the potential to offer enough delta-V to lift one's apoapsis to a respectably high orbital radius.

But nobody is proposing a Mach 3 air launch because:

• Hypersonic separation is a difficult nut to crack.
• Mach 3 and 24 000 meters still makes a rather crappy first stage (typically they get you to Mach 6 or 7 at 100 km).
• You are still going to need a pretty large multi-stage rocket with a first stage that will only be marginally smaller.
• Nobody wants the cost of developing a one-off XB-70 just to have it fly once a month or less.

Edited June 22, 2016 by Nibb31

[StevieC]

Fair enough on most of those points, but I will remind people that once you're at 70 thousand feet, you're above 90% of the atmosphere, by mass.

[StrandedonEarth]

It sounds good in theory, but also remember that even at Mach 3 / 2000mph, you're still a lot of dV away from orbital velocity @ 17,500mph

[wumpus]

I suspect the most important thing for a stratolaunch rocket would be that you could cut atmospheric pressure by 90% or so, making your engines (and nozzle) operate at near vacuum all the way up.  KSP has taught me to underestimate this, but everything I've read about real rocket design says it is critical.  It might be the most important part of a such a launch (well, that and simply flying to a better latitude for no inclination burns).

[Laie]

Hey hey hey, wait a second.

From playing Realism Overhaul, I'm under the impression that it takes on the order of 1500-2000m/s just to get to Mach1@10km. That's only a fraction, but not exactly a small one. In terms of mass, that's 40-60% of the entire rocket.

In principle, small LVs suffer the most from drag, and hence should benefit the most from being carried out of the worst atmosphere. Besides, the smaller the rocket, the wider the choice of planes that could carry it to altitude. The standard example was an SDI satellite killer. Less than a hundred kg payload, but as a standalone LV it would have required MRBM-class infrastructure. Air-launched it's just another kind of missile that goes on the standard mount points.

I won't try to sell anyone on that concept for civilian launches. Especially not for 5t payloads (that's a lot). I just want to point out that air launch is not as obviously silly on the face of it as some here seem to believe.

[lysol]

Another pro is being able to launch in bad weather on the ground.

[PB666]

12 hours ago, Laie said:

Hey hey hey, wait a second.

From playing Realism Overhaul, I'm under the impression that it takes on the order of 1500-2000m/s just to get to Mach1@10km. That's only a fraction, but not exactly a small one. In terms of mass, that's 40-60% of the entire rocket.

In principle, small LVs suffer the most from drag, and hence should benefit the most from being carried out of the worst atmosphere. Besides, the smaller the rocket, the wider the choice of planes that could carry it to altitude. The standard example was an SDI satellite killer. Less than a hundred kg payload, but as a standalone LV it would have required MRBM-class infrastructure. Air-launched it's just another kind of missile that goes on the standard mount points.

I won't try to sell anyone on that concept for civilian launches. Especially not for 5t payloads (that's a lot). I just want to point out that air launch is not as obviously silly on the face of it as some here seem to believe.

A modern turbojet engine uses the mass from the air to accelerate it, the exhaust velocity is cut to a few hundred meters per second affording a very high thrust momentum  per fuel burnt the equivilent ISP is in the 10 of 1000s. There are two types of drag in flying, there is form drag (differentially side drag) that decreases per unit volume with increased radius, thus if mass is proportional to volume, the side drag per unit mass is reduced as mass increases. There is also lift associated drag, that doesn't change with volume. Side drag makes speed a problem with smaller objects, and because speed is a problem it disallows smaller craft from flying at very high altitudes, except in cases with massive wings, such as the solar impulse.

The benefit of being large is the ability to gain altitude, but that requires higher powered jet engines that have large air throughputs.

Your typical rocket at liftoff experiences almost no lift drag or form drag because it is not moving, all of its losses are gravity in the first 15 or 20 seconds of flight. As it travels up it begins to experience form drag and side drag, but in most cases side drag almost disappears and the boundary layer collapses back on the plume, the force is thus the MACH force on the nose-cone, this typically occurs between 15,000 and 30,000 feet where air is 2/3 to 1/3 surface density and declining rapidly, beyond this a rockets speed and upward motion move it out of air quickly. There would be a definite benefit of launching a rocket from 10,000 feet on the equator because the surface gravity is less, its horizontal momentum is higher 1/0.867 that of 30' North. Experienced gravity declines more rapidly, It experiences the air pressure at each moment of flight 10,000 feet higher than being launched at sea level, and the ISP is higher.