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Paul Allen's Stratolaunch Finally Flies The World's Biggest Plane (geekwire.com)
"Stratolaunch, the aerospace venture founded by the late Microsoft co-founder Paul Allen, sent the world's biggest airplane into the air today for its first flight test," report GeekWire.
The twin-fuselage plane, which incorporates parts from two Boeing 747 jumbo jets and has a world-record wingspan of 385 feet, took off from Mojave Air and Space Port in California for a flight that lasted two and a half hours. For more than seven years, Stratolaunch has been working with Mojave-based Scaled Composites on the project, which aims to use the plane as a flying launch pad for orbital-class rockets. The first flight test had been anticipated for months. "We finally did it," Stratolaunch CEO Jean Floyd said today during a briefing.
Stratolaunch's plane, which has been nicknamed Roc after a giant mythical bird, took off at 6:58 a.m. PT and went through a series of in-flight maneuvers, including roll doublets, yawing maneuvers, pushovers and pull-ups, steady heading side slips and simulated landing approach exercises. Stratolaunch said it reached a maximum speed of 189 mph and maximum altitude of 17,000 feet.... The plan ahead calls for further tests over the next 12 to 18 months, with the aim of getting the plane fully certified by the Federal Aviation Administration. Stratolaunch has already struck a deal to use Northrop Grumman's Pegasus XL rocket to send payloads weighing as much as 816 pounds (370 kilograms) to low Earth orbit...
Stratolaunch's air-launch system is designed to carry multiple rockets up to an altitude of about 40,000 feet, and then drop them into the air to fire up their rocket engines. The advantage of such a system is that it can take off from any runway that's long enough to accommodate the plane, fly around bad weather if need be, and launch a satellite into any orbital inclination.
Stratolaunch CEO Jean Floyd said their team had dedicated the flight to Paul Allen.
"[A]s the plane lifted gracefully from the runway, I did whisper a 'thank you' to Paul for allowing me to be part of this remarkable achievement."
Stratolaunch's plane, which has been nicknamed Roc after a giant mythical bird, took off at 6:58 a.m. PT and went through a series of in-flight maneuvers, including roll doublets, yawing maneuvers, pushovers and pull-ups, steady heading side slips and simulated landing approach exercises. Stratolaunch said it reached a maximum speed of 189 mph and maximum altitude of 17,000 feet.... The plan ahead calls for further tests over the next 12 to 18 months, with the aim of getting the plane fully certified by the Federal Aviation Administration. Stratolaunch has already struck a deal to use Northrop Grumman's Pegasus XL rocket to send payloads weighing as much as 816 pounds (370 kilograms) to low Earth orbit...
Stratolaunch's air-launch system is designed to carry multiple rockets up to an altitude of about 40,000 feet, and then drop them into the air to fire up their rocket engines. The advantage of such a system is that it can take off from any runway that's long enough to accommodate the plane, fly around bad weather if need be, and launch a satellite into any orbital inclination.
Stratolaunch CEO Jean Floyd said their team had dedicated the flight to Paul Allen.
"[A]s the plane lifted gracefully from the runway, I did whisper a 'thank you' to Paul for allowing me to be part of this remarkable achievement."
Launching rockets from airplanes has been done before but the plan with Stratolaunch is to do so on a larger scale with functionally a bigger rocket. There are some advantages and some disadvantages. One major disadvantage is that there's functionally a size limit: one cannot really put that large a rocket on a plane (and the fact that to get this to work they need to use what is by multiple metrics the largest airplane ever reflects that).
The plane is functioning to some extent like a reusable first stage, but a plane isn't likely to go as high or as fast as as a true first stage, like the Falcon 9's first stage, so it isn't the same as having a true reusable first stage in terms of power.
At the same time, a plane is a well understood, reliable technology. Another connected advantage of air launch is that one is much less beholden to weather events. since the plane can fly above or around bad weather. The Falcon 9 in contrast frequently needs to be delayed due to weather issues (which are made worse in its case because it is a very long and thin rocket); one does have things like the Soyuz which is able to launch in functionally blizzard conditions, but that's pretty rare for a rocket and is in a large part due to the fact that it was originally designed to be an ICBM.
It's only the world's biggest plane in terms of wingspan. In terms of weight, payload, or length, Soviet An-225 remains the biggest.
To me, the most interesting aspect of Stratolaunch is the flexibility enabled by positioning your "launch pad" at just the right place. But I don't know if that will be enough to sustain them in the current market. A lot has changed since they started working on this project, with SpaceX and Rocket Lab both providing "budget" launch services, not to mention Blue Origin waiting in the wings. It will be interesting to see how/if they manage to find their niche.
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That's one big bleeping plane.
Scaled really loves the dual fuselage design. Why? Looks fragile.
What happens if the right and left elevators get out of sync? Just seems like a bad design.
Joking aside, that has to be a weird feeling for the pilots to be so far away from the centerline of the plane. Not that you're going to fly anything this (amazingly, incredibly) massive by the seat of your pants anyway, but still.
This is a spectacular piece of aerospace engineering, basically a huge flying wing built to lift several hundred ton boosters.
The recent SpaceX Falcon 9 Heavy launch with full booster recovery destroys the economic advantage of air launch.
SpaceX's success indicates that launching can become a refuel and repeat process, so there is no need for a hugely expensive aircraft launch vehicle. Especially as that aircraft has limited speed and range and requires an enormous runway to operate from, which undercuts the idea that it can launch to any azimuth from anywhere.
From a business perspective, the operation was successful, but the patient died. Sad.
The Pegasus XL is currently launched (singularly) from an L1011; honest question, but what benefit does Stratolaunch hav over Orbital besides “we can carry three?”
The biggest advantage is lower air pressure. Rocket engines must keep the pressure of the exhaust gas higher than the atmosphere the launch in. This means the engines at sea level launch will have a lower exhaust speed and therefore be less efficient.
Next you don't have to push through 40,000 feet of atmosphere. Rockets launched from sea level do not accelerate at their maximum rate because they want to reduce loss due to air resistance.
Third is flexibility of launch location. You can now launch from anywhere your plane can get to. Launching from the equator to geostationary orbit is easier than going form south Florida.
Last you start a little higher and with an initial velocity. This is probably the least advantage but it still counts. Rockets are all about change in velocity and its an exponential equation. Want to go an extra 1500m/s double the size of your rocket. So a little initial altitude and velocity can mean a huge difference in the amount of fuel needed to reach your intended orbit.
That's Donald Trump's head.
The amount of energy you gain from air launching is a tiny fraction of what's required to get the payload into orbit. Optimistically assuming air launch at 40k' (12k metres) and 600mph (270 metres per second), the energy of 2.2lb (1kg) of payload at launch is approximately 275 kJ but to achieve a 100 mile (160 km) orbit travelling at 17,500 mph (7,800 metres per second) 32 Megajoules of energy is required for the payload. Interestingly enough, I did a quick check of my math and found out that the 32 MJ required for putting a 1kg payload into orbit is the theoretical minimum - the practical minimum is around 100 MJ (https://space.stackexchange.com/questions/4330/how-much-energy-is-required-to-put-1-kg-in-leo). So, the "first stage" of air launch provides 0.85% of the energy required for the theoretical minimum for orbital flight and about 0.275% for the practical amount.
It should be pointed out that if you count the air launch as the "first stage", you actually have a three stage booster - all the current and planned air launched boosters are two stages. So, if air launching was a true "first stage" and the booster only had one stage, then you could argue that you're reusing the first stage but, as it is, you're still throwing away as much expensive booster hardware as if you were launching from the ground - AND you're spending money on an aircraft to get it where the booster's first stage can light.
Now, there is the supposed advantage that air launching is more flexible and doesn't have weather issues. If you look at Orbital Science's Pegasus air launch record, it's no better than any other launcher because of weather (it's a factor when flying an airliner with a 50,000 lb external load) and the extra precision required to launch at the correct point of time and space (which is more of a factor because during the first few seconds of launch, the energy expended to get the booster correctly lined up is quite insignificant compared to when you're already in the air).
Air launch seems to be an obviously more efficient method of launching space craft, but when you look at it practically, there is no economic or even scheduling advantage.
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In my (admittedly layman's) understanding, one nice thing about launching from the ground is that you can keep your rocket aimed precisely straight-up at the moment of ignition (and hopefully thereafter as well, until it's time to deliberately modify the rocket's attitude).
Having the rocket strapped to (and then released from) an aircraft, on the other hand, introduces the possibility that when the rocket's engines ignite, the rocket will be pointing in some inappropriate direction and won't be able to re-orient itself "in time" (for whatever definition of "in time" applies in order for it to make it to its intended orbit).
Does anyone know the technique they plan to use to make sure their rockets are pointed in the right direction when they start producing thrust?
I don't care if it's 90,000 hectares. That lake was not my doing.
When an airplane lands in crosswinds (i.e. wind direction is not parallel to the runway) its nose is pointed at an angle to the runway. When it touches down, the plane needs to abruptly swivel so the nose is pointed down the runway, as now it is being directed by wheels rather than wind. In strong crosswinds, this operation looks really freaky. Here are crosswind landing videos.
Here we have a plane with landing gear much much further apart than any ordinary plane. I wonder whether this makes it harder to do that abrupt swivel? If so, the plane will have much greater restrictions on crosswind landings.
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For those wanting the unadulterated experience, including the slightly oddways landing.
https://www.youtube.com/watch?...
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Air launch has a lot of advantages - the lower air density allows smaller rockets to be efficient (less air drag, square / cube law), lower exhaust pressure (higher ISP, or lower chamber pressure), etc. Also allows a wide choice of launch sites and orbit inclinations. and avoids most of the weather. So I see the advantage.
I'm surprised though that they didn't use a conventional bomber that is designed to release large objects at high altitude. I'd think it would be possible to get a surplus de-militarized B52, or Bear or something. Rocket technology is already pretty restricted due to potential missile applications, so getting permission to use an old bomber doesn't seem like it would be that difficult. A B52 can drop >50,000 pounds at high altitude, which should be enough for >1 ton to orbit.
Engineering a new plane is enormously expensive. Its great that they did it, but it seems a surprising use of their resources.
This thing really does look like something the Soviets would build. Or try to build.
Pegasus already has a launch platform. Should the existing Pegasus aircraft retire, they can get another. It's easy and (relatively) cheap.
Seems to me that that Stratolaunch is simply looking for a payload now, and they need Pegasus far more than Pegasus needs Stratolaunch. In fact Stratolaunch is likely the most expensive way to launch a Pegasus. That's bad news for Stratolaunch.