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fredymac

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Longer duration video with better shots of landing. With Allen gone I wonder if the money to fully prove out the flight envelope will be provided. Maybe the Missile Defense Agency could use the aircraft to carry their boost phase laser. Not sure how high up this thing can fly or if MDA could settle for a lower altitude for a demonstration test.

 
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sferrin

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That looked like an exciting landing. :eek:
 

kitnut617

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sferrin said:
That looked like an exciting landing. :eek:
Watching the first flight of the XP-82 after it's restoration a few weeks ago, the pilot did the same thing when it landed. Admittedly, doing it in something this big certainly would get the pucker factor up I think.
 

Byeman

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fredymac said:
Longer duration video with better shots of landing. With Allen gone I wonder if the money to fully prove out the flight envelope will be provided. Maybe the Missile Defense Agency could use the aircraft to carry their boost phase laser. A
There is no laser. Also, it is a poor platform for such a task.
 

fredymac

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Byeman said:
There is no laser. Also, it is a poor platform for such a task.

They are developing one. How do you know what the turbulence field is? Did you run the numbers? What shape did you use for the pod structure? Can you show me your Schlieren graphs? You provoke this kind of response if you don't provide any details for the brush off replies you give.
 

Jemiba

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Please, back to a reasonable tone !
 

steelpillow

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I do agree that arbitrary payloads in arbitrary flight regimes could lead to unwelcome oscillatory modes, via interaction of arbitrarily distributed mass and aerodynamic characteristics. Even with the fuselages roc steady (sic), the wing is so wide and thin that its centreline could oscillate significantly. Vertical displacement and pitching come immediately to mind. Due to the structural size, these oscillations would be of unusually low frequency, which means unusually high absolute displacement for a given energy and therefore also higher structural stresses.

Each such flight configuration would need to be de-risked through modelling, backed byl in-flight characterization of the airframe characteristics.

But I do not agree that a degree in rocket science is necessary before such a risk may be taken seriously on a public forum. Rather, the burden lies on the proposer to "run the numbers, design the shape of the pod structure and produce [wind tunnel data]" in order to demonstrate that the regime is safe and, in the case of a precision-aimed laser, adequately stable. Such risks are commonplace enough. Many UK residents will remember the Millennium Bridge fiasco, when this supposedly stable bridge opened and an unexpected vibration mode developed when under operational loads. Nor in an aerospace context do I need to dwell on the safety regime under which the 737 MAX stall-management system was deployed. The "no rocket scientist has proved it unsafe" argument just does not wash.
Of course, low-amplitude, low-frequency unwanted oscillatory modes may be corrected for using software-controlled electro-mechanical systems. But that will not help if there is insufficient mechanical damping to prevent destructive divergence from building up under some unforeseen flight condition.

On the other hand, if all that can be achieved then a central payload will be better insulated from engine-induced vibration than say the US experimental laser installations in a 747 were. But I remain unconvinced that the Roc would be a laser scientist's first choice.
 

fredymac

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All fine and well but “arbitrary”? This vehicle was designed from the outset to carry a large, heavy cylindrical mass under the center wing. A presumption of malfeasance or incompetence is necessary to imply the principal design function will fail. It will undoubtedly require fine tuning and validation but again, how do you presume aerodynamic, stress, and turbulence modelling was not rigorously conducted by the engineering staff during the design process? Indeed, g-loads and vibration levels would have to be assessed because customers would require that information for their payloads.

I am not too familiar with the Millennium Bridge. I thought it was a curved pedestrian bridge and the design staff forgot about the pedestrians (shifting masses on balance and load). I didn’t follow that story but I assume a finding of design failure would have resulted. It is always possible for a company culture to go dysfunctional and allow a serious fault to get by. In this country that would be followed by all kinds of lawsuits and possible bankruptcy.
 

steelpillow

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I think you are taking the suggestion that something might fail as a claim that it will.
In the case of the Millennium Bridge, the specification of the structural analysis software was prescribed by national engineering safety standards. However the standards did not recognise the particular failure mode that occurred and so the software did not check for it. That the mode was induced by pedestrians instinctively adjusting their step to the oscillations was pure coincidence from the structural point of view. The safety standards have since been updated to include the particular oscillatory mode and I understand this has happened globally.
Similarly, nobody is presuming that Stratolaunch have not done their job properly. But there remain those mathematically arbitrary conditions - the known unknowns - that one cannot model in advance. And the aerodynamic-inertial coupling of a large, heavy pod on a slim, wide wing is a biggie.
 

fredymac

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I am no expert on the state of Finite Element Analysis and Computational Fluid Dynamics software so I can't assess how comprehensively it can cover all possible perturbations. On the other hand, I would think experts who use the software would have a feel for where they are uncertain of the results and give themselves some design margin. In the end, its a matter of expertise and thorough consideration of risks.
 

Mark Nankivil

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I have yet to see a failed design from Scaled Composites - time will tell if Roc maintains that track record. I wonder far more about a mssion for the airframe with Paul Allen's passing and the near immediate cancellation of the efforts for those launch loads.

Anyone know how long before the expected Pegasus XL launch?

Enjoy the Day! Mark
 

Byeman

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They are developing one. How do you know what the turbulence field is? Did you run the numbers? What shape did you use for the pod structure? Can you show me your Schlieren graphs? You provoke this kind of response if you don't provide any details for the brush off replies you give.
It is intuitively obvious. The "pod" would have poor visibility being slung between two fuselages. That is why the ABL had the mirrors in the nose.

And what does Schlieren have anything to do with it? It will fly nowhere close to trans-sonic.
 

Byeman

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On the other hand, if all that can be achieved then a central payload will be better insulated from engine-induced vibration than say the US experimental laser installations in a 747 were. But I remain unconvinced that the Roc would be a laser scientist's first choice.
It would be less insulated, since it is on the wing which the engines are attached.
 

FighterJock

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Anyone know what has become of the Spaceplane (shuttle) that was under development until the death of Paul Allen? The Stratolaunch website is still showing that it is active, yet I have seen news on the web that it has been canceled. :confused:
 

Moose

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Anyone know what has become of the Spaceplane (shuttle) that was under development until the death of Paul Allen? The Stratolaunch website is still showing that it is active, yet I have seen news on the web that it has been canceled. :confused:
Stratolaunch has cancelled all their rocket/spacefraft development. At the moment, they plan to fly Pegasus and hope to attract a customer with their own vehicle.
 

FighterJock

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That is sad that they have cancelled all rocket/spacecraft development, let's hope that Pegasus gets customers soon so that they can restart development at some point in the future. By the way the Spacecraft was my favorite of all the Stratolaunch designs.
 

TomS

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Pegasus is a really marginal launcher right now. Its cost ($55 million plus) isn't that far off a Falcon 9, for much, much less payload. It's going to have to cut its price by about 80% to compete against other launchers coming out in its weight class. That includes the Virgin Orbit LauncherOne (target price of $12 million), another air-launched option coming soon if you really need to hit weird orbits.
 

steelpillow

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On the other hand, if all that can be achieved then a central payload will be better insulated from engine-induced vibration than say the US experimental laser installations in a 747 were. But I remain unconvinced that the Roc would be a laser scientist's first choice.
It would be less insulated, since it is on the wing which the engines are attached.
I trust you are aware that there are no engines on the wing centre section. Are you suggesting that there is an absorbent coupling between a one-piece wing and bolt-on fuselage structures? Otherwise, being out along the next wing section is further from the engines than being in the separating fuselage.
 

Byeman

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The ABL laser was nose mounted for turbulence minimization, not visibility.
It was visibility. It allowed the turret the most view. turbulence is not a problem from the side of the fuselage. See SOFIA aircraft
 

fredymac

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It was visibility. It allowed the turret the most view. turbulence is not a problem from the side of the fuselage. See SOFIA aircraft
Here is the ABL with a 1.5 meter telescope mounted externally in a sealed, rotating turret.
Also, the predecessor ALL with a 60cm telescope mounted externally in a sealed rotating turret. Experience with this configuration (boundary layer, turbulence) led to the switch to the ABL location.

And finally, a picture of SOFIA. Notice what's missing. I've mentioned before that my profession is optical engineering (including HEL systems). And that is all the time I am going to spend on this.
 

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sferrin

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Supposedly the Russian IL-76 laser testbed also has its laser in a nose turret. (I say "supposedly" because all the pictures I can find show a turret-shaped fairing rather than an actual turret.)
 

steelpillow

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Sad to hear, but hardly surprising. It's a traditional way to write off development costs and sell on a flyable airplane to someone with the cash and knowledge to maintain it and market its services. Let's hope that happens here.
Not sure what that says about the Pegasus XL planned as its first payload, though.
 

sferrin

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They can park the Composite Goose next to the Spruce Goose.
 

FighterJock

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Really sad about Stratolaunch. Let's hope that someone (Virgin Galactic) takes Stratolaunch over, I cannot believe that they would just let them disappear.
 

dan_inbox

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Hmm. It would be sad if their project made sense technically.
Since it doesn't make much sense (in that the gains from the the launch out of that plane are marginal at best), then it is only normal that reason prevails.
In my book, it was a billionnaire's pet toy, not a great project to advance space conquest.

I wish I had the money to afford such a toy, but foremost I wish I had the wisdom to choose one that makes sense.
Orbital's Stargazer L-1011 launching Pegasus was a failure decades ago. Making a bigger/costlier/hightech-ier version of it wasn't a good idea...
 

RanulfC

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In general the concept was plausible but the execution, especially without a launch vehicle in the pipeline, was more than a bit lacking. Frankly I never saw the need for such a large carrier vehicle unless you payload was enormous. Which it likely was planned to be considering I'd noted elsewhere I "know" I'd seen this design before:
(Page 12 Figure 1.2 "Gryphon LV and Eclipse Carrier Aircraft")

17,000lbs to LEO or 7,900lbs to GEO with an overall gross mass of around 500,000lbs for the LV.

But again the question is do you NEED that much payload?

"Swiftlaunch" only put around 1800lbs into LEO but didn't need a specialiced Carrier Aircraft;

Whereas AirLaunch planned about 10,000lbs total to LEO with a 3STO LV massing around 207,000lbs all up at take off which used a (not really extensivly) modified 747 carrier aircraft which for the $15 million dollar cost can also 'part-time' as an air-tanker. http://mae.engr.ucdavis.edu/faculty/sarigul/papers/AIAA-2008-7835.pdf
(Note this report points out while a custom carrier has advantages the cost has pretty always been found prohibitive and this is only going to reinforce that conclusion)

I'd also like to point out that while Orbital's Pegasus and Stargazer were expensive that's not actuall Orbital's fault and neither were really a 'failure' in the role and mission. Orbital originally had a deal to use the NASA/AF B-52s but it was made clear that they would not support a higher flight rate or incrased mission tempo so Orbital would need to fund and develop their own carrier aircraft hence they built Stargazer. Secondly the Air Force and DoD did not choose to puruse more launchers which had been something they indicated during the testing and development program. Since that had been a factor used to caculate costs per launch the cost went up significantly.

Loss or expected revenue of course led to lack of development on more advanced models of the Pegasus in the usual feed-back loop and here we are.

Randy
 

martinbayer

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As I've pointed out *repeatedly* (and without any objectively substantiated refutation, I might add) in this thread, Allen's ultimate goal, while (for whatever reason - expediency?) taking admittedly highly questionable intermediate steps like expendable rocket stages (yuck!) into consideration, was evidently a fully reusable winged HTHL TSTO RLV, a both worthwhile and promising objective for advancing the goal of a cost effective, reliable, and responsive LEO transportation shuttle. There is of course absolutely no guarantee whatsoever that his conceptual design would have converged and delivered the intended benefits, but I for one deeply mourn his passing, for it represents just one more missed opportuniy for at least trying to help us leave our earthly creadle for good.

Martin
 
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RanulfC

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As I've pointed out *repeatedly* (and without any objectively substantiated refutation, I might add) in this thread, Allen's ultimate goal, while (for whatever reason - expediency?) taking admittedly highly questionable intermediate steps like expendable rocket stages (yuck!) into consideration, was evidently a fully reusable winged HTHL TSTO RLV, a both worthwhile and promising objective for advancing the goal of a cost effective, reliable, and responsive LEO transportation shuttle. There is of course absolutely no guarantee whatsoever that his conceptual design would have converged and delivered the intended benefits, but I for one deeply mourn his passing, for it represents just one more missed opportuniy for at least trying to help us leave our earthly creadle for good.

Martin
While not 'refuting' your point and yes it's always sad when a concept doesn't pan out, especially one that has possibities such as StratoLaunch, my specific point was there where numerous other ways that the "goal" could have been approached that likley would have had a greater margin of operations and larger chance of overall success. The "Roc"would have made a lot more sense if someone else had been already or willing to build a launch vehicle but none of the "partners" had either the resources or the willingness to do so with any reasonable launch vehicle that Alan would not also be paying the majority of.

SpaceX was a conflict of interest from the announment, there was simply no incentive for them to take the idea seriously. Orbital was a questionable choice I think as I don't see anyway to make a "Pegasus II" work at the scale proposed. (Granting that it would have been a pretty obviously 'easier' LV to design from a structures point of view, economics and reusability were unlikely) I don't know that they didn't but I'd have thought AirLaunch/T-Space would have been high on the list to reach out to as most of their designs could use the Roc's capabilites. (I'd have loved to have seen Alan or someone grab up the X-34s at some point if only to get them out of the weather and away from the wreckers) "Black Ice" was a good concept but the amount of work and money needed to even get to a prototype stage would have been on par with the Roc itself. The sub-scale Dreamchaser concept was interesting but still didn't really address the launch vehicle issues and concerns.

Desiging and building a credible "Horizontal" launch vehicle isn't a trivial task and especially when you get into the vastly better performing LV designs with liquid propellant tankage to worry about.

A fully reuable launch vehicle was likely not initially to be due to the up-front costs, even a partially reusable may have been a step to far but not having ANYTHING in the wings waiting on Roc to fly...

Randy
 

martinbayer

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Randy,

I completely concur with your whole analysis above, including that potential alternative approaches might have been more promising, such as (in my very own personal view) for example a fully reusable winged VTHL TSTO with liquid rocket propulsion, parallel staging and propellant crossfeed, but in today's space transportation landscape you take what you can get (or not)...

Martin
 
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Flyaway

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The world's largest airplane is up for sale for $400 million

Holding company Vulcan is seeking to sell Stratolaunch at $400 million, people familiar with the matter tell CNBC.

Vulcan is the investment conglomerate of late billionaire Paul Allen.

There are several possible suitors for Stratolaunch, especially the most active space industry trio of billionaires: Elon Musk, Jeff Bezos and Richard Branson.

While it's unknown if either Musk's SpaceX or Bezos' Blue Origin is pursuing a purchase of Stratolaunch, people familiar tell CNBC that Vulcan has spoken to Branson about selling Stratolaunch to his Virgin Group.
 

FighterJock

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It will be interesting to see who eventually buy's Stratolaunch it is not that expensive at $400 million.
 

Grey Havoc

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I suspect that things like support equipment and spare parts inventory will be sold separately.
 
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