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Author Topic: Stratolaunch  (Read 46162 times)

Offline blackstar

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Re: Stratolaunch
« Reply #15 on: December 14, 2011, 11:31:47 am »
Well, I'm sure Scaled is up to the task. Building a very large aircraft is not without its problems but it's been done before, unlike everything else they managed to do since 2004, which had no precedents. I worry more about the other components of the system and financial backing than Scaled's ability to pull this off.

What is the largest aircraft built by Scaled?

Offline Hobbes

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Re: Stratolaunch
« Reply #16 on: December 14, 2011, 11:46:51 am »
Probably White Knight 2
Quote
General characteristics

    Payload: 17,000 kg (37,000 lb)[24] to 50000 ft.; 200 kg satellite to LEO[25] (test)    Length: 24 m (79 ft)    Wingspan: 43 m (141 ft)    Height: ()    Powerplant: 4 ◊ Pratt & Whitney Canada PW308 turbofanPerformance    Service ceiling: 21.3 km (70,000 ft [24])
(from Wikipedia)
« Last Edit: December 14, 2011, 12:39:58 pm by Hobbes »

Offline Byeman

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Re: Stratolaunch
« Reply #17 on: December 14, 2011, 11:48:11 am »
Not only that; the fuselages can be designed for a payload of 0 kg; as far as I can see they only exist to provide a place for the undercarriage, crew and tailplanes. Not a floor that can carry 100 tons.

No, they will be carrying LOX tanks for topping off the booster

Offline AeroFranz

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Re: Stratolaunch
« Reply #18 on: December 14, 2011, 12:51:41 pm »
Buying two 747s isn't going to be cheap. For the several hundred M$ they'll cost, you can do an awful lot of design and fabrication work. Your clean-sheet design will also have much lighter fuselages, so it'll have more payload.

All previous points made about superiority of clean sheet design duly noted and for the most part agreed on. I do not think however on the cost issue. Who says you have to buy new 747s? IIRC, the NASA B-52 mothership had the lowest flight hours of ANY B-52 in the air force, so airframe life is not an issue. As a matter of fact, a few years back I spent an evening at the Voyager diner at the Mojave airport a couple of doors down from Scaled. From there I could see dozens of airliners parked out in the desert for lack of use (9/11? economic downturn?), I can't remember if there were 747s...but you get my point, I am sure that there are 747s to be had, and I don't think you can build a new 1.2M pounds design for less than it takes to buy two used 747s that benefitted from ~50 years of high volume production.
The catch in using low wing aircraft lies in having to hang the payload underneath the wing, hence the better suitability of C-5s. Hell, not all the remaining air force C-5s are being converted to -Ms, maybe you can get a deal on a couple that are redundant. Too bad the old models are down half the time for maintenance.
All modern aircraft have four dimensions: span, length, height and politics.   TSR.2 got the first three right - Sir Sydney Camm

Offline mboeller

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Re: Stratolaunch
« Reply #19 on: December 15, 2011, 12:52:26 am »
IMHO,
using 2 747 fuselages would not work because of the cantilever-design with the wing below the fuselage.
Redesigning the fuselage with a wing above the fuselage would cost more than a clean-sheet design.

AAAdrone

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Re: Stratolaunch
« Reply #20 on: December 15, 2011, 10:00:24 am »
IMHO,
using 2 747 fuselages would not work because of the cantilever-design with the wing below the fuselage.
Redesigning the fuselage with a wing above the fuselage would cost more than a clean-sheet design.

I don't really think those are 747 fuselages.  Like Stargazer said the cross-section of each fuselage appears to be too small for them to be made by sticking two 747s together.  The fuselages might be designed from the ground up to look conveniently similar to a 747 though.  The engines and supposedly the landing gear and possibly even the avionics will also be taken from the 747.  Basically the general superstructure is clean-sheet but the more intricate and complex parts are off the shelf if my beliefs are correct.

Offline Gridlock

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Re: Stratolaunch
« Reply #21 on: December 15, 2011, 11:04:57 am »
If you're working largely in CFD then is there an economy available in utilising well-understood and -modelled airframe shapes? My guess.


In the modelling and therefore final shape I mean, not that it's made of 747.

Offline blackstar

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Re: Stratolaunch
« Reply #22 on: December 16, 2011, 07:03:05 am »
There's a good assessment here:

http://www.newspacejournal.com/2011/12/15/stratolaunch-a-contrarian-view/

I think this is the key point:

"Instead, Iíve been pondering this question: what problem does this system solve? Thatís the key question for any business venture, not just a launch vehicle company. What can Stratolaunch do that others canít do, or do as well or as cheaply? Air launch has its advantages, but also carries with it some disadvantages and other issues. That, coupled with what the company has released about its technical capabilities, leads me to wonder if the Stratolaunch system will really be that competitive over more conventional launch systems in service or under active development today."

However, look also at his discussion of the aircraft cost. This is going to be an expensive aircraft. Standard cost models indicate that it will cost billions.

And I think it is also worth asking if it is realistic for Scaled to build such a large aircraft. Scaled builds unique, one-of-a-kind, relatively small and low-powered/low-performance vehicles. This aircraft is of a size that only the major aerospace contractors have experience with.

I think this is a vanity project and it's going to fold in a few years. It certainly doesn't serve any part of the over-saturated launch market that requires these unique capabilities.

Offline RanulfC

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Re: Stratolaunch
« Reply #23 on: December 16, 2011, 08:21:38 am »
Ok, what's "known" so far:
 
- StratoLaunch has already purchased two (2) used 747s they will be stripping for landing gear and avionics. (They said yesterday they are looking to purchase a third for parts also)
 
- Fuselage and wings will be all "new" build, the main reason the cockpit area looks like that of a 747 is because they plan to use the layour and controls from a 747.
 
- Carrier Aircraft will be runway limited to at least 12,000ft runways, however it will NOT be a "dedicated" Air-Launch-Vehicle but will be capable of carrying out-sized and specialty cargo with a 9,200 mile range
 
- The rocket will be a "varient" of the Falcon-9 with 5 engines in the first stage, 1 engine in the second stage. @13,500lbs to LEO delivery
 
- The video (here:https://www.facebook.com/video/video.php?v=202596223158748) shows the whole flight profile.
 
- Both Space-X (booster) and Scaled (Carrier Aircraft) are on-board as "contractors" only. Allen is listed as an "investor" while Rutan is on the "board" as well as Mike Griffin (yes that one :) )
 
Pretty much everything else is speculation and a lot of it. According to the press conference Allen ONLY decided to release as much as he has because construction of the hanger in Mojave is supposed to start soon and that's something they would not be able to "hide" from competitiors.
 
Oh and for the general FYI I found this paper at NTRS which gives some pretty good information on the hows and whys of Air Launch To Orbit economics:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070002822_2007001607.pdf
 
Randy

RGClark

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Re: Stratolaunch
« Reply #24 on: December 16, 2011, 09:27:30 am »
There's a good assessment here:

http://www.newspacejournal.com/2011/12/15/stratolaunch-a-contrarian-view/

I think this is the key point:

"Instead, Iíve been pondering this question: what problem does this system solve? Thatís the key question for any business venture, not just a launch vehicle company. What can Stratolaunch do that others canít do, or do as well or as cheaply? Air launch has its advantages, but also carries with it some disadvantages and other issues. That, coupled with what the company has released about its technical capabilities, leads me to wonder if the Stratolaunch system will really be that competitive over more conventional launch systems in service or under active development today."
However, look also at his discussion of the aircraft cost. This is going to be an expensive aircraft. Standard cost models indicate that it will cost billions.
...

 DARPA with its Alasa program wants this type of airlaunch system but for small payloads, ca. 100 pounds:

Article:
US Military Wants to Launch Satellites from Airplanes.
Date: 07 November 2011 Time: 12:08 PM ET
http://www.space.com/13529-darpa-military-airplane-satellite-launches.html

 Curiously, they also expect it to fly by 2015. For launches this small, it might work to use a WhiteKnight2 for the carrier aircraft, and a Falcon 1 first stage as the rocket, perhaps shrunk slightly to fit within the carrying capacity of the WhiteKnight2.
 DARPA is basing the feasibility of such air launch systems on this study:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015353_2011016245.pdf

 A focus of this study was on systems intermediate in size between DARPA's Alasa and Stratolaunch, with for example the carrier aircraft being 747-sized and the rocket being of Falcon 1e size.


    Bob Clark

RGClark

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Re: Stratolaunch
« Reply #25 on: December 16, 2011, 09:44:33 am »
...
Oh and for the general FYI I found this paper at NTRS which gives some pretty good information on the hows and whys of Air Launch To Orbit economics:
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070002822_2007001607.pdf
 
Randy

 The benefits of air launch go beyond just the speed and altitude attained. This is discussed in this report:

Air Launching Earth-to-Orbit Vehicles: Delta V gains from Launch Conditions and Vehicle Aerodynamics.
Nesrin Sarigul-Klijn University of California, Davis, CA, UNITED STATES; Chris Noel University of California, Davis, CA, UNITED STATES; Marti Sarigul-Klijn University of California, Davis, CA, UNITED STATES
AIAA-2004-872
42nd AIAA Aerospace Sciences Meeting and Exhibit, Reno, Nevada, Jan. 5-8, 2004
http://pdf.aiaa.org/preview/CDReadyMASM04_665/PV2004_872.pdf  [first page only]

 The conclusions are summarized in this online lecture:

A.4.2.1 Launch Method Analysis (Air Launch).
"For a launch from a carrier aircraft, the aircraft speed will directly reduce the Δv required to attain LEO. However, the majority of the Δv benefit from an air launch results
from the angle of attack of the vehicle during the release of the rocket. An
ideal angle is somewhere of the order of 25į to 30į.
"A study by Klijn et al. concluded that at an altitude of 15250m, a rocket launch with the
carrier vehicle having a zero launch velocity at an angle of attack of 0į to
the horizontal experienced a Δv benefit of approximately 600 m/s while a launch
at a velocity of 340m/s at the same altitude and angle of attack resulted in a
Δv benefit of approximately 900m/s. The zero launch velocity situations can
be used to represent the launch from a balloon as it has no horizontal velocity.
"Furthermore, by increasing the angle of attack of the carrier vehicle to
30į and launching at 340m/s, a Δv gain of approximately 1100m/s
was obtained. Increasing the launch velocity to 681m/s and 1021m/s produced a
Δv gain of 1600m/s and 2000m/s respectively.
"From this comparison, it can be seen that in terms of the Δv gain, an airlaunch is
superior to a ground launch. As the size of the vehicle decreases, this superiority
will have a larger effect due to the increased effective drag on the vehicle."
https://engineering.purdue.edu/AAE/Academics/Courses/aae450/2008/spring/report_archive/reportuploads/appendix/propulsion/A.4.2.1%20Launch%20Method%20Analysis%20(Air%20Launch).doc

 A speed of 340 m/s is a little more than Mach 1, while subsonic transport aircraft typically cruise
slightly below Mach 1. So the delta-V saving could still be in the range of 1,000 m/s with air launch,
a significant savings by the rocket equation.


    Bob Clark

Offline blackstar

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Re: Stratolaunch
« Reply #26 on: December 16, 2011, 09:55:05 am »
DARPA is basing the feasibility of such air launch systems on this study:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015353_2011016245.pdf


This is the interim report. The final report has been completed and should be available somewhere.

Offline ouroboros

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Re: Stratolaunch
« Reply #27 on: December 17, 2011, 12:36:13 am »
Smart to make the carrier aircraft capable of carrying outsize cargo (via a cargo pod?) as a revenue generator when not busy throwing rockets, much like the AN-225. There is also the potential market for sale/lease to other air launchable systems (XCOR Lynx? Possible B-52 replacement for NASA for air drop experiments? DARPA and friends?) but the big takeaway is the listed range of 1300nm. This underlies a possible launch approach of going uprange, launching, and recovering the first stage of the rocket via a "glide forward" methodology rather than the traditional "boost back" profile, allowing recovery of all assets at the same airport/spaceport and not taking a large deltaV hit on the rocket for the recovery boost.

The rocket concept is shown with a Pegasus style wing (is this truly necessary for the trajectory?), but nothing is stopping SpaceX from adapting their Hopper VTVL related technologies they are developing for the recoverable Falcon 9 first stage to do a vertical propulsive landing for stage recovery.

Offline Skyblazer

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Re: Stratolaunch
« Reply #28 on: December 17, 2011, 02:07:32 am »
I don't deem it irrational to build a carrier aircraft that can carry just about any kind of self-propelled vehicle to high altitudes. Programs like Pegasus, X-37, X-38, X-40, X-43, X-51, SpaceShipOne, SpaceShipTwo, XCOR Lynx, and many others have relied or will rely on this capability. I wouldn't be surprised if the operating and maintenance costs of a Stratolauncher were distinctly smaller than those of a Stratofortress. Having one platform that can fit the bill with less costs and operate from US ground, especially now that NASA itself is using foreign launch sites for its own programs, seems pretty seems sensible to me.

Offline Byeman

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Re: Stratolaunch
« Reply #29 on: December 17, 2011, 05:29:21 am »
This underlies a possible launch approach of going uprange, launching, and recovering the first stage of the rocket via a "glide forward" methodology rather than the traditional "boost back" profile, allowing recovery of all assets at the same airport/spaceport and not taking a large deltaV hit on the rocket for the recovery boost.


Huh?  Yeah, right.  How many airports do you think can support this aircraft?  There are just couple that can be used to "launch" the configuration.