Can the space shuttle take off from a runway?

[KeithP]

It can't lift off from a runway but NASA has a special treadmill that it can take off from.

-KeithP

 

[CP5670]

Originally posted by: KeithP
It can't lift off from a runway but NASA has a special treadmill that it can take off from.

-KeithP

:laugh:

 

[jagec]

The shuttle is designed for reentry, not gliding OR flying. However, it's a good enough glider to keep itself in the sky at low enough speeds to land, while being a bad enough glider to be able to fall through the atmosphere without skipping back out into space or burning its wings off.

Originally posted by: astroidea

Originally posted by: KillerCharlie

Originally posted by: Modelworks
The difference between a glider and airfoil is big. Gliders do not provide lift, they rely on resistance against the surface. It is like someone dropping a sheet of paper versus one balled up. The paper isn't generating lift, its using the air resistance to slow it down as it falls.

Airfoil move air at one speed over the top and another below it, lower air pressure above the wing allows the higher air pressure below the wing to push the wing up, that is lift.

I'll stick with what a NASA engineer said " The shuttle is a rock in a controlled free-fall to the ground"

"Gliders do not provide lift?" They provide lift in the exact same way any other airplane wing does. The orbiter is definitely creating lift during its decent. In the latter half of reentry it's acting just like any other glider.

did you even read his explanation? air resistance != lift

His "explanation" is an atrocity. If we were comparing an airplane against a dandelion seed, sure, we could make a scientifically meaningful distinction between the controlled "lift" which the former produces and the "air resistance" provided by the latter (which allows it to gain altitude under a limited set of circumstances, but which cannot be steered).

But according to his explanation, if you turn off the engine in a Cessna, you have magically removed its airfoil. And if you strap a small engine to a glider, you have magically turned its "wind resistant blades" into airfoils.

Put a 747 and the Space Shuttle side by side in a wind tunnel and turn it on, and both of them will register lift. The SS doesn't produce as much at the same angles of attack, but it certainly produces.

 

[coxmaster]

Looks like everybody seems to have explained it fairly well. Overall answer, no.. It couldnt. Well, it could probably but it wouldnt fly long. The wings do create lift, but they create more drag than lift on landing

 

[Aberforth]

Originally posted by: coxmaster
Looks like everybody seems to have explained it fairly well. Overall answer, no.. It couldnt. Well, it could probably but it wouldnt fly long. The wings do create lift, but they create more drag than lift on landing

Yeah, that's sound about right. There is this thing called spoilers which increases the drag.

 

[KIAman]

Actually, the space shuttle creates more drag than lift at higher speeds. At approach speeds (around 200mph), the shuttle's Lift-to-drag (or glide) ratio is just around a Concorde's at 4.5. The Concorde's design allows the ratio to almost double at cruising speeds.

The shuttle, will lose it's ratio until it is just a 1 at hypersonic speeds (atmospheric re-entry).

Allowing for oversimplification, the shuttle's thrust need only to overcome the overall drag produced to take off. I don't have any info on how much drag a Shuttle makes but here is a comparison.

A 747 has a LTD ratio of around 15. It's 4 engines produce a total of 253,000lbs of thrust combined. It has a maximum takeoff weight of 970,000lbs.

The space shuttle LTD ratio is 4.5 (and decreases while going faster). It's 3 rocket engines produce a total of 393,800lbs combined. It is around 230,000lbs.

I'll let someone smarter do the math to get liftoff speeds. My guess is that the Shuttle is capable of liftoff but lack the fuel (rocket propulsion) to keep the main engines firing for longer than a few minutes (if at all, considering its fuel source is the main tank during takeoff).

 

[coxmaster]

Glide ratio doesnt really make much difference here.. Glide ratio only involves unpowered flight.

 

[KillerCharlie]

Originally posted by: coxmaster
Glide ratio doesnt really make much difference here.. Glide ratio only involves unpowered flight.

As the guy above you said, "glide ratio" is the same as L/D. It matters every bit as much in powered flight as unpowered flight. The shuttle creates more lift than drag when landing.

 

[jagec]

Originally posted by: coxmaster
Glide ratio doesnt really make much difference here.. Glide ratio only involves unpowered flight.

Glide ratio gives you an idea of how much power you need to sustain flight or take off. In other words, to take off, a craft must produce enough lift to overcome gravity. Since lift is proportional to drag (that ratio is the glide ratio), it also must produce enough thrust to overcome drag.

(the weight doesn't matter as much as you'd think, since you can always make the runway longer and ensure that the craft doesn't have to climb steeply after takeoff)

Originally posted by: KIAman
A 747 has a LTD ratio of around 15. It's 4 engines produce a total of 253,000lbs of thrust combined. It has a maximum takeoff weight of 970,000lbs.

The space shuttle LTD ratio is 4.5 (and decreases while going faster). It's 3 rocket engines produce a total of 393,800lbs combined. It is around 230,000lbs.

I'll let someone smarter do the math to get liftoff speeds. My guess is that the Shuttle is capable of liftoff but lack the fuel (rocket propulsion) to keep the main engines firing for longer than a few minutes (if at all, considering its fuel source is the main tank during takeoff).

We can wing the math to do a basic comparison: A 747 will need 970,000 lbs of lift to balance the weight, divide by the LTD ratio to get a drag of 64,600lbs of drag, about a quarter of the engines' max combined rating.

The shuttle needs 230,000, divide by LTD to get 51,100 lbs of drag, about an eighth of the engines' max combined rating.

Suffice to say, thrust isn't the problem. I'm having a lot of trouble finding how much fuel is carried onboard, but one link indicates that the deorbit burn lasts three minutes. If this burn was done at the full 393,800 lb rating (1.71 g at full weight, accelerating perpendicular to the force of gravity), this would leave the shuttle traveling at 3,000 m/s, or ~Mach 7.

Now I doubt that the shuttle can perform a full burn for three minutes with onboard fuel stores, and I doubt that this thrust rating is maintained throughout the speed envelope, but during the actual deorbit burn (which occurs in space, where thrust ratings are lower), the shuttle decreases its speed from 28,000km/h to 24,000 km/h using onboard fuel stores.

So I don't doubt that the shuttle possesses the capability to take off under its own power, if you REALLY wanted to.

Originally posted by: Aberforth

Originally posted by: coxmaster
Looks like everybody seems to have explained it fairly well. Overall answer, no.. It couldnt. Well, it could probably but it wouldnt fly long. The wings do create lift, but they create more drag than lift on landing

Yeah, that's sound about right. There is this thing called spoilers which reduces the drag.

Spoilers are designed to INCREASE drag and slow aircraft down.

 

[bsobel]

Suffice to say, thrust isn't the problem. I'm having a lot of trouble finding how much fuel is carried onboard, but one link indicates that the deorbit burn lasts three minutes. If this burn was done at the full 393,800 lb rating (1.71 g at full weight, accelerating perpendicular to the force of gravity), this would leave the shuttle traveling at 3,000 m/s, or ~Mach 7.

Your thinking of the wrong engines. The main engines are for launch, they are NOT used for reentry.

 

[Aberforth]

Originally posted by: Aberforth

Yeah, that's sound about right. There is this thing called spoilers which reduces the drag.

Spoilers are designed to INCREASE drag and slow aircraft down.[/quote]

whoops...I meant Increase. :beer:

 

[Nathelion]

Originally posted by: RedSquirrel
I've always wondered why they can't just create a giant solonoid, put the rocket in it (rebuild it in thick steel / possibly some lead for shielding the inside). Apply billions of volts for a few seconds to the solonoid, WHAM, in space.

They'd need doctors at the space station to rectify the whiplash of all people onboard though, and the aim better be good.

But seriously, if done properly, would that concept work? Save on shitload of fuel. (probably brown out every single power plant in the contry in the process though)

That's called a gauss gun (IIRC?), and you'd need one heck of a solenoid. I think a railgun would be better since it has a longer acceleration phase, but while we're at it, why don't we do it like Jules Verne and build a big cannon?

 

[AeroEngy]

Originally posted by: bsobel

Suffice to say, thrust isn't the problem. I'm having a lot of trouble finding how much fuel is carried onboard, but one link indicates that the deorbit burn lasts three minutes. If this burn was done at the full 393,800 lb rating (1.71 g at full weight, accelerating perpendicular to the force of gravity), this would leave the shuttle traveling at 3,000 m/s, or ~Mach 7.

Your thinking of the wrong engines. The main engines are for launch, they are NOT used for reentry.

Exactly, as I stated earleir the only engines they can fire without the external fuel tank are the OMS (Orbital Maneuvering System). There are only two at the rear of the shuttle for a combined thrust of 12,000 lbf. This is not even close to enough to take off or for that matter maintain any kind of level flight in the atmosphere.

The whole discussion of gliders wings not being airfoils is ridiculous and doesn't make any sense. A glider's wings are just designed to be as efficient as possible given its flying conditions. The wings are typically something like a MH 32 airfoil with a high aspect ratio. That gives a very good glide ratio or lift-to-drag ratio. Note: these are exactly the same mathematically L/D or Vforward/VDown. It is just that a glider has wings designed for a L/D of something like 60 to 70 and the space shuttle has a L/D of about 1.

Also please note that an airfoil can be symmetric and still function quite well. Meaning at 0° angle of attack the same air flow over the wing as under. Refer to pretty much all fighter aircraft. They just have to have an angle of attack > 0 to maintain level flight. So in short any cross section of any wing is an airfoil there is just an infinite number of shapes and therefore flight characteristics they can have

 

[SonicIce]

Originally posted by: KIAman
My guess is that the Shuttle is capable of liftoff but lack the fuel (rocket propulsion) to keep the main engines firing for longer than a few minutes (if at all, considering its fuel source is the main tank during takeoff).

I was just thinking, what if they filled the whole cargo bay with a fuel tank?

 

[AeroEngy]

Originally posted by: SonicIce

Originally posted by: KIAman
My guess is that the Shuttle is capable of liftoff but lack the fuel (rocket propulsion) to keep the main engines firing for longer than a few minutes (if at all, considering its fuel source is the main tank during takeoff).

I was just thinking, what if they filled the whole cargo bay with a fuel tank?

The main engines together burn 1,035 gallons per second. The Cargo bay is 60x15ft so the volume is around 79,300 gallons (assumed it was a cylinder and no gaps between fuel and oxidizer tanks).

So that is at most 76 seconds of burn time. Pretty short flight.

 

[jagec]

Originally posted by: AeroEngy

Originally posted by: SonicIce

Originally posted by: KIAman
My guess is that the Shuttle is capable of liftoff but lack the fuel (rocket propulsion) to keep the main engines firing for longer than a few minutes (if at all, considering its fuel source is the main tank during takeoff).

I was just thinking, what if they filled the whole cargo bay with a fuel tank?

The main engines together burn 1,035 gallons per second. The Cargo bay is 60x15ft so the volume is around 79,300 gallons (assumed it was a cylinder and no gaps between fuel and oxidizer tanks).

So that is at most 76 seconds of burn time. Pretty short flight.

Sure, but 76 seconds at THAT thrust rating would get anything in the air, which satisfies the conditions of the thread.

 

[randay]

the shuttle takes off.

 

[OCedHrt]

Originally posted by: Modelworks

Originally posted by: bsobel

Originally posted by: astroidea

Originally posted by: KillerCharlie

Originally posted by: Modelworks
Planes that take off have airfoil shaped wings designed so that air moves at a different rate over the top than the bottom to create lift. The shuttles are not designed like that, they are shaped for gliding and not providing lift.

Okay, not to be mean, but you're completely wrong.

You're not mean, but mornic pointing out someone is wrong without stating reasons.

It should be pretty obvious that wings provide lift, and there is no real difference between 'gliding' and 'providing lift'. Otherwise, what you have is a rock on a ballistic trajectory.... Whats missing is thrust to make the wings remotely useful. The shuttles only power is really inertia from launch...

The difference between a glider and airfoil is big. Gliders do not provide lift, they rely on resistance against the surface. It is like someone dropping a sheet of paper versus one balled up. The paper isn't generating lift, its using the air resistance to slow it down as it falls.

Airfoil move air at one speed over the top and another below it, lower air pressure above the wing allows the higher air pressure below the wing to push the wing up, that is lift.


I'll stick with what a NASA engineer said " The shuttle is a rock in a controlled free-fall to the ground"

To provide more information: http://en.wikipedia.org/wiki/Lift_(force)

 

[Rubycon]

Originally posted by: Modelworks

I'll stick with what a NASA engineer said " The shuttle is a rock in a controlled free-fall to the ground"

I've heard the same thing said by another NASA physicist too.

Also the SSME Rocketdyne motors are not designed for horizontal operation across the ground? Would the pumps and gimbal mounts even work correctly like this?

 

[gsellis]

The shuttle is a lifting body. It is designed for unpowered flight. But if you think it cannot fly, you would be incorrect. As noted above, the landing flare would be just a thought before impact otherwise.

 

[JTsyo]

Reading through the thread, I think I see the misunderstanding. Some are talking "lift" to mean the lift force is greater than the weight. When the lift is just the force component opposite of gravity. Even if the lift is less than the weight, you still have some lift but not enough to maintain altitude.

If we just look at the equation for lift (L = 1/2 (density) V^2 S (coeff of lift)) we can see that if you get enough velocity, you can overcome the other variables and get your lift to equal your weight. Trouble is the lower the other variables the faster you need to go and the higher the drag.

 

[jagec]

Originally posted by: Rubycon

Originally posted by: Modelworks

I'll stick with what a NASA engineer said " The shuttle is a rock in a controlled free-fall to the ground"

I've heard the same thing said by another NASA physicist too.

Also the SSME Rocketdyne motors are not designed for horizontal operation across the ground? Would the pumps and gimbal mounts even work correctly like this?

I think that we all pretty much assumed that the initial answer to the question "Can the space shuttle take off from a runway" (under its own power, without any modifications from its current setup) was "No."

Then, we wanted to answer the question "Can the space shuttle take off from a runway" (under any circumstances, preferentially with its own engines and whatever modifications might be necessary to ensure proper fuel delivery). That starts boiling down to semantics...and the completely unnecessary confusion about the exact definition of "lift" didn't help.

 

[Jeff7]

Originally posted by: herm0016
the aerodynamics are built for gliding, and it even sucks at that. I don't know if it would generate enough lift.

I seem to have memory of an astronaut saying that reentry is like flying and landing a giant brick.

 

[KIAman]

Astronauts say that because the LD ratio, the change of LD ratio depending on speed, and aerodynamics of a Shuttle are atypical of a flying device. It also probably has minimal control surfaces to make maneuvering even harder than typical aircraft.

Thinking about it, the first manned spacecraft literally dropped strait down during reentry relying on minimal maneuvering thrusters and parachutes. I wonder why we devote such a huge amount of complicated machinery and weight to try to make a flight-like body in our shuttle?

 

[AeroEngy]

Originally posted by: KIAman
Astronauts say that because the LD ratio, the change of LD ratio depending on speed, and aerodynamics of a Shuttle are atypical of a flying device. It also probably has minimal control surfaces to make maneuvering even harder than typical aircraft.

Thinking about it, the first manned spacecraft literally dropped strait down during reentry relying on minimal maneuvering thrusters and parachutes. I wonder why we devote such a huge amount of complicated machinery and weight to try to make a flight-like body in our shuttle?

Probably why the Orion will be back to a capsule.