Can Serenity Fly in Hover Mode?

  • Thread starter Lancelot59
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In summary, the conversation discusses the feasibility of a ship like the one shown in the image being able to fly well. There is a debate about stability while hovering and the comparison is made to the Osprey, which uses a lot of technology and computers for flight stabilization. The idea of making an RC version of this ship is also discussed, with the consensus being that it would require a high-tech flight stabilization system. Some participants suggest that a quadrotor would be a more feasible project.
  • #1
Lancelot59
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I'm sure many of you are familiar with this ship:
(Sorry, I couldn't find a smaller image that was any good)
foomandoonian_01_1024x768.jpg


I wonder if this ship would actually fly very well. One of the many things I'm interested in doing is RC aircraft, because I don't have the vast fortunes required to build these things full scale.

In normal flight mode I think it follow the jet fighter school of flying more so where it gets pushed through the air and guided along by the wings/control surfaces. The wings that go out to the main engines actually do have an airfoil shape to them. They have a very large camber, but I guess the big engines take care of the drag.

What I wonder about is stability while hovering. Some schematic type images place the wing mounts half way up the ship, and there's about an equal amount of ship above and below that point. As you can see in the picture only the cargo bay area which also has some other rooms is actually below the mounts. The rest of the ship rides above that, save the large rear end.

I was discussing this with my friend and he pointed out that with something like an osprey the lift force is well above the centre of gravity:
v22osprey01.jpg


Which I think would be a big contributing factor to stability. Serenity's centre of mass is tricky to figure out without having a proper schematic, but it's safe to say the centre of gravity is much closer to the level of the lifting force. Also, with the osprey the lift force generated by the propellers is at the end of the engine nacelles. With jets where do you place the lift force?

Lateral axis stability would seem to be fine. To me it looks like the mass of the bridge and other stuff up front would be balanced by the huge rear end. Something else I see being an issue is that pretty much all your control would be derived from thrust vectoring. What do you guys think?
 
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  • #2
The Osprey has a lot of computers on board. This is how it can fly at all. Each of the propellers have cyclic control, like a helicopter. A sensor suite detects motions of the aircraft and then corrects that motion with adjustments to the propellers. The fact that it has pendulum stability (the center of mass is lower then the propellers) helps, but that does not provide stability of the aircraft. Despite all the technology in the osprey, it doesn't fly well and crashes a lot.

Applying this to Serenity, The lift comes from the bottom of the turbines, but it is where the nacels are attached to the ship that counts. Imagine a see-saw, the legs are down low, but the "lift" is where the axle attaches to the board.

To make an RC Serenity, you would need a pretty high tech flight stabilization system. Good luck
 
  • #3
I don't know much about how a vehicle like this works but it looks to me like it would be extremely difficult to properly balance something like the Osprey. A slight forward or backward shift in the CG would cause the vehicle to pitch up or down and I don't see how you could counteract this. I suppose the V-22 has some measure against this. Does anyone know how anything about the Osprey's longitudinal stability?

I think a quadrotor would be a much easier project. Not to say that quadrotors are easy, because they are not, I have designed and built one from scratch before. Actually the vehicle I built was like a quadrotor but had an additional degree of freedom, the propulsion units were gimbaled about a single axis so they could rotate in a manner similar to the V-22 Anyways, I bet a quadrotor is more doable then designing and building your own version of the V-22. Either way, just getting the vehicle to hover can be a difficult project.

As for the Serenity, I don't think it would actually fly. Those "wings" are really small. The camber won't really matter in terms of drag, that extremely unaerodynamic fuselage will see to that. :smile:
 
  • #4
jackn007 said:
The Osprey has a lot of computers on board. This is how it can fly at all. Each of the propellers have cyclic control, like a helicopter. A sensor suite detects motions of the aircraft and then corrects that motion with adjustments to the propellers. The fact that it has pendulum stability (the center of mass is lower then the propellers) helps, but that does not provide stability of the aircraft. Despite all the technology in the osprey, it doesn't fly well and crashes a lot.

Applying this to Serenity, The lift comes from the bottom of the turbines, but it is where the nacels are attached to the ship that counts. Imagine a see-saw, the legs are down low, but the "lift" is where the axle attaches to the board.

To make an RC Serenity, you would need a pretty high tech flight stabilization system. Good luck
I see. Thanks for the info.

RandomGuy88 said:
I don't know much about how a vehicle like this works but it looks to me like it would be extremely difficult to properly balance something like the Osprey. A slight forward or backward shift in the CG would cause the vehicle to pitch up or down and I don't see how you could counteract this. I suppose the V-22 has some measure against this. Does anyone know how anything about the Osprey's longitudinal stability?

I think a quadrotor would be a much easier project. Not to say that quadrotors are easy, because they are not, I have designed and built one from scratch before. Actually the vehicle I built was like a quadrotor but had an additional degree of freedom, the propulsion units were gimbaled about a single axis so they could rotate in a manner similar to the V-22 Anyways, I bet a quadrotor is more doable then designing and building your own version of the V-22. Either way, just getting the vehicle to hover can be a difficult project.

As for the Serenity, I don't think it would actually fly. Those "wings" are really small. The camber won't really matter in terms of drag, that extremely unaerodynamic fuselage will see to that. :smile:
That's why I said it wouldn't really fly the way you would expect it to. The jets just throw the ship around. It does have a pretty horrible front surface area. The real sore thumb that stick out is the cargo bay underneath. Other then that it's pretty good.

I'm just looking to learn more. A project like this is years off, once I have more knowledge, and experience.

Good question too. How exactly would you control pitch?
 
  • #5
Those toy RC helicopters stabilise themselves pretty well without computers.

They have a gyroscope attached by linkges to control the pitch of the blades. When it starts to tilt to the left the gyroscope increases the lift on the left side blades and reduces it on the right, bringing it upright again.
 
  • #6
Unrest said:
Those toy RC helicopters stabilise themselves pretty well without computers.

They have a gyroscope attached by linkges to control the pitch of the blades. When it starts to tilt to the left the gyroscope increases the lift on the left side blades and reduces it on the right, bringing it upright again.

I'm familiar with how cyclic and collective mixing works. Unfortunately for something like serenity I wouldn't have that ability.
 
  • #7
From an Aero Controls guy:

Your forward flight would not go so well from that configuration. However, hovering could be done. Controlling pitch would be done with servomotors attached directly to your power plant. You would probably be better off using a small turbine rather than props since your Lift/Weight would be pretty low.
 
  • #8
If you truly wanted forward flight, you would probably just end up with an Osprey on turbines.
 
  • #9
viscousflow said:
If you truly wanted forward flight, you would probably just end up with an Osprey on turbines.

Except I guess the osprey has actual control surfaces as far as I know. Serenity would fly solely on thrust vectoring.Unless I modified the supports for the turbines to have some control surfaces. I guess the rear end could also have some too, it has those panels that open to use the main drive. Perhaps those could be used as a really bad rudder?
 
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  • #10
Its tough, I put pencil to paper and I can't see anything remotely close to conventional flight happening without some horizontal stabilizer. Once those turbines rotate forward during transition, you need something to counteract that moment. Also after transition during forward flight, you'll have some moment at the aerodynamic center (AC) which moves, so having your CG at the AC won't help much either.

As for vertical tail you should be ok without one, since all lateral movement would be controlled by differential thrust. Directional and longitudinal stability (plus coupling) are your greatest worry.
 
  • #11
Honestly its not an impossible design, however it would certainly have to be tweaked a bit from the design on the image and end up a bit sophisticated.
 
  • #12
viscousflow said:
Its tough, I put pencil to paper and I can't see anything remotely close to conventional flight happening without some horizontal stabilizer. Once those turbines rotate forward during transition, you need something to counteract that moment. Also after transition during forward flight, you'll have some moment at the aerodynamic center (AC) which moves, so having your CG at the AC won't help much either.

As for vertical tail you should be ok without one, since all lateral movement would be controlled by differential thrust. Directional and longitudinal stability (plus coupling) are your greatest worry.
That's what I was thinking too. The ship's rear end has these panels that open up, I wonder if those could be used to control horizontal stability in flight.

viscousflow said:
Honestly its not an impossible design, however it would certainly have to be tweaked a bit from the design on the image and end up a bit sophisticated.
I would think so. It would pretty much end up flying itself. I picked up a book on aircraft design, I still need to sit down and go through it properly. I can rig up some experiments and see how they go. Garry's Mod is great for this sort of rough stuff. The physics on the source engine aren't super amazing, but they should work fine for these tests.
 
  • #13
Lancelot59 said:
That's what I was thinking too. The ship's rear end has these panels that open up, I wonder if those could be used to control horizontal stability in flight.

It seems to me like it would just be easier to put another turbine in the back. It could just be fixed in place an provide the necessary thrust for pitch control.
 
  • #14
Lancelot59 said:
I picked up a book on aircraft design, I still need to sit down and go through it properly.

If you're serious about doing a first pass design on this I would start off with the dynamics first. Do a 6dof free body diagram and understand where your forces and moments are coming from (see Steven's and Luis, 'Flight Simulation ...' or Robert C. Nelson 'Flight Stability and Automatic Control, etc). Next you'd want to do what I call a "conceptual trim analysis" meaning you want to see what forces and moments are necessary to trim out the craft in a particular configuration (hover, conventional flight, etc..).

Then you can do a static and then an aerodynamic analysis to gain a deeper understanding of where these forces and moments are coming from for a particular configuration.

In my view its important to start at fundamental dynamic analysis first for new configurations.

Good luck.
 
  • #15
hey - hate to break it to you, but the firefly class could probably fly UP well enough, but after that, it just flies using the heat-shield material known as "artistic license," and would have burned up on re-entry.
 
  • #16
viscousflow said:
If you're serious about doing a first pass design on this I would start off with the dynamics first. Do a 6dof free body diagram and understand where your forces and moments are coming from (see Steven's and Luis, 'Flight Simulation ...' or Robert C. Nelson 'Flight Stability and Automatic Control, etc). Next you'd want to do what I call a "conceptual trim analysis" meaning you want to see what forces and moments are necessary to trim out the craft in a particular configuration (hover, conventional flight, etc..).

Then you can do a static and then an aerodynamic analysis to gain a deeper understanding of where these forces and moments are coming from for a particular configuration.

In my view its important to start at fundamental dynamic analysis first for new configurations.

Good luck.
Well I'd like to build some less complicated stuff and get some experience first.
 
  • #17
Lancelot59 said:
Well I'd like to build some less complicated stuff and get some experience first.

That works too :tongue:
 
  • #18
viscousflow said:
That works too :tongue:
RandonGuy88 asked a good question further up, which is how does a v-22 maintain longitudinal stability?
Also, your suggestion of using another turbine in the back for pitch control brings up a question of how long it would be able to fly before running out of fuel.

I'll try to rig up the test rig in Gmod tonight.
 
  • #19
During which phase of flight? During hover longitudinal stability is maintained by two actuators built right into the power plants. It uses sophisticated control systems to control them. As it transitions to forward flight the actuators rotate the power plants. After this the V-22 becomes a conventional aircraft with longitudinal stability maintained by the twin tail.
 
  • #20
Lancelot59 said:
Also, your suggestion of using another turbine in the back for pitch control brings up a question of how long it would be able to fly before running out of fuel.

Ehh not very long. Truth is, for mini turbines the efficiency is already very low. Furthermore, the aerodynamic efficiency of the serenity I assure you is very low also. To compound these inefficiencies you're building a vtol aircraft which is again inefficient since you have to carry around the dead weight used to hover in forward flight.

I'm actually designing my own RC VTOL aircraft which will be hovering in the weeks to come. Mine is using EDFs though not turbines since its been done already. Check this one out: some guy's design with turbines

To be honest, I'm not sure about run times of those small turbines but you'd be lucky to squeeze 10 minutes out of that design.
 
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  • #21
viscousflow said:
During which phase of flight? During hover longitudinal stability is maintained by two actuators built right into the power plants. It uses sophisticated control systems to control them. As it transitions to forward flight the actuators rotate the power plants. After this the V-22 becomes a conventional aircraft with longitudinal stability maintained by the twin tail.

For an RC aircraft I'm not sure I'd be able to do that. When I get on gmod tonight I think I'll experiment with a thruster on the back end for pitch control.
 
  • #22
viscousflow said:
Ehh not very long. Truth is, for mini turbines the efficiency is already very low. Furthermore, the aerodynamic efficiency of the serenity I assure you is very low also. To compound these inefficiencies you're building a vtol aircraft which is again inefficient since you have to carry around the dead weight used to hover in forward flight.

I'm actually designing my own RC VTOL aircraft which will be hovering in the weeks to come. Mine is using EDFs though not turbines since its been done already. Check this one out: some guy's design with turbines

To be honest, I'm not sure about run times of those small turbines but you'd be lucky to squeeze 10 minutes out of that design.


Yeah, I guess building it would be pretty pointless then. 10 minutes isn't very long. Although if I made it bigger I could hold more fuel.
 
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  • #23
Lancelot59 said:
Yeah, I guess building it would be pretty pointless then. 10 minutes isn't very long. Although if I made it bigger I could hold more fuel.

Well actually in the RC world that's a pretty darn good run time. But be careful with just making it bigger. You'll need to keep tabs on Thrust/Weight for hover, and Thrust required to maintain Lift.

Don't let the the first one fall below 1 (obviously), and don't let the second one get out of hand or else you'll be running 80mph + just to get Lift = Weight.
 
  • #24
viscousflow said:
Well actually in the RC world that's a pretty darn good run time. But be careful with just making it bigger. You'll need to keep tabs on Thrust/Weight for hover, and Thrust required to maintain Lift.

Don't let the the first one fall below 1 (obviously), and don't let the second one get out of hand or else you'll be running 80mph + just to get Lift = Weight.

I guess, fuel isn't the lightest thing in the world. Although I wonder how much I could improve the range by having ducted fans run off of batteries. Wouldn't be as faithful to the old design, but it should work the same.
 
  • #25
Of course the main problem with this ship is it's an impossible design for a spaceship because the thrust vector doesn't fire through the center of mass. That fact makes this show almost unwatchable to me because I keep thinking, with all the trouble they went to to make this show believable, they never talked to an engineer or a scientist who would have pointed out this obvious flaw.
 
  • #26
Henry Harris said:
... the thrust vector doesn't fire through the center of mass.
What makes you say that?

http://www.labarc.com/Black/Side.jpg [Broken]
 
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  • #27
DaveC426913 said:
What makes you say that?

http://www.labarc.com/Black/Side.jpg [Broken]

I agree, I don't see how it isn't going through the centre of mass.
 
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  • #28
I probably shouldn't have said anything. I don't want to ruin anybody's enjoyment of the series, but here goes.

Serenity is designed like an airplane. An airplane has wings that give it a vertical force component that keeps it in the air. If you look at the design of Serenity, the control cabin is set vertically above the horizontal line of force just like the design of an airplane. If such a spacecraft were designed in real life, it would pinwheel trying to take off. Look at the way NASA designs spacecraft . The center of mass is always directly in front of the the center line of the rocket engine force vector. Serenity looks like a jet-powered seaplane, not even remotely like a spacecraft .

If you have trouble visualizing this, imagine Serenity set vertically on a NASA launchpad. Trace the thrust line of the engines and notice how the control cabin stick out to one side. It should be obvious that Serenity would never get off the launch pad.
 
  • #29
Henry Harris said:
I probably shouldn't have said anything. I don't want to ruin anybody's enjoyment of the series, but here goes.

Serenity is designed like an airplane. An airplane has wings that give it a vertical force component that keeps it in the air. If you look at the design of Serenity, the control cabin is set vertically above the horizontal line of force just like the design of an airplane. If such a spacecraft were designed in real life, it would pinwheel trying to take off. Look at the way NASA designs spacecraft . The center of mass is always directly in front of the the center line of the rocket engine force vector. Serenity looks like a jet-powered seaplane, not even remotely like a spacecraft .

If you have trouble visualizing this, imagine Serenity set vertically on a NASA launchpad. Trace the thrust line of the engines and notice how the control cabin stick out to one side. It should be obvious that Serenity would never get off the launch pad.

In the vertical case it might tip backwards because of the moment generated by the cockpit section, however the back end is set lower than the engines, and it's fairly heavy from what I remember.
 
  • #30
Henry Harris said:
I probably shouldn't have said anything. I don't want to ruin anybody's enjoyment of the series, but here goes.
Nonsense. We're all rational here.
Henry Harris said:
Serenity is designed like an airplane. An airplane has wings that give it a vertical force component that keeps it in the air. If you look at the design of Serenity, the control cabin is set vertically above the horizontal line of force just like the design of an airplane.
This is not a compelling argument. Just because it has some elements that superficially resemble an airplane does not make it an airplane.

Henry Harris said:
If such a spacecraft were designed in real life, it would pinwheel trying to take off.
As you point out, as long as the thrust is aligned with the CoM, you're OK.

Henry Harris said:
Look at the way NASA designs spacecraft . The center of mass is always directly in front of the the center line of the rocket engine force vector.
Lousy comparison.


Henry Harris said:
Serenity looks like a jet-powered seaplane, not even remotely like a spacecraft .
Again...

Henry Harris said:
If you have trouble visualizing this, imagine Serenity set vertically on a NASA launchpad. Trace the thrust line of the engines and notice how the control cabin stick out to one side. It should be obvious that Serenity would never get off the launch pad.
You're comparing a Saturn V to a Firefly??

I am fairly certain the Wright brothers would take one look and an F104 Starfighter and laugh their butts off.
 
  • #31
DaveC426913 said:
You're comparing a Saturn V to a Firefly??

I am fairly certain the Wright brothers would take one look and an F104 Starfighter and laugh their butts off.

I tend to agree here. Just because it's unconventional doesn't mean it wouldn't work. That vertical moment looks like it could be balanced out. The clockwise moment from the cockpit balanced by the counterclockwise moment of the rear end, which sits lower than the pylons, and the centre of mass.
 
  • #32
Lancelot59 said:
I tend to agree here. Just because it's unconventional doesn't mean it wouldn't work. That vertical moment looks like it could be balanced out. The clockwise moment from the cockpit balanced by the counterclockwise moment of the rear end, which sits lower than the pylons, and the centre of mass.
Yes. We don't actually know how the mass is distributed internally. For all we know, the bilge is very dense.


Additionally, as far as the aerodynamic stability Henry is concerned about, even aircraft today must be computer-controlled to be stable. Many modern jet fighters are minutely controlled on the order of 30 times per second to remain in stable flight, without which they would break up faster than they could fall out of the sky.

It is not unreasonable to suppose that a spacecraft an indeterminate number of centuries in the future might be similarly sophisticated.
 
  • #33
DaveC426913 said:
Yes. We don't actually know how the mass is distributed internally. For all we know, the bilge is very dense.Additionally, as far as the aerodynamic stability Henry is concerned about, even aircraft today must be computer-controlled to be stable. Many modern jet fighters are minutely controlled on the order of 30 times per second to remain in stable flight, without which they would break up faster than they could fall out of the sky.

It is not unreasonable to suppose that a spacecraft an indeterminate number of centuries in the future might be similarly sophisticated.

As some people pointed out to me when I first had this idea, it wouldn't be an easy thing to accomplish. However it is certainly within the realm of possibility. It might not fly as well as it did on the show, but it could certainly fly. We've certainly made much stranger things take flight:

http://books.google.ca/books?id=xSg...sult&ct=result&redir_esc=y#v=onepage&q&f=true
 

1. Can Serenity fly in hover mode?

Yes, Serenity is capable of flying in hover mode. It is equipped with vertical take-off and landing (VTOL) technology, allowing it to hover in place and maneuver in tight spaces.

2. How does Serenity fly in hover mode?

Serenity uses a combination of jet propulsion and thrust vectoring to achieve hover flight. The engines on the sides of the ship provide vertical lift, while the nozzles can be angled to control the direction of movement.

3. What is the maximum altitude Serenity can reach in hover mode?

The maximum altitude for Serenity in hover mode is approximately 10,000 feet. However, this may vary depending on the weight and cargo of the ship, as well as external factors such as weather conditions.

4. How long can Serenity stay in hover mode?

Serenity can stay in hover mode for an extended period of time, as long as it has enough fuel and power. The exact duration will depend on the specific model and any modifications made to the ship.

5. Can Serenity fly in hover mode on other planets?

Yes, Serenity is designed to be able to fly in hover mode on other planets with similar atmospheric conditions to Earth. However, modifications may be needed to adjust for differences in gravity and air density.

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