Stratolaunch without final conception

Stratolaunch, competitive project to Virgin SpaceShipTwo or more to LauncherOne, after almost five years of development probably will change its final shape.

It is possible that Paul Allen (Microsoft co-founder and founder of Vulcan Inc. and Stratolaunch Systems) will be forced to reinstall engines back into his two Boeing 747 from picture above. Conception of two stage launch vehicle based on very large plane carrying rocket suspended between two fuselages seems to be threatened. When Vulcan Aerospace (Company established in 2015 as a part of Vulcan Inc.) President Chuck Beames in interview from 17 November 2015 given to Wall Street Journal claimed, that Stratolaunch should be redesigned with taking into account new trends in the space industry it was clear that for Stratolaunch changes are closing with huge steps.

Stratolaunch project was born in 2011 as a new launch vehicle for commercial purposes. Paul Allen after founding Stratolaunch Systems (with SpaceX, Scaled Composites and Dynetics as system integrator) decided to put project in hands of Burt Rutan and with team of forty employees and budget of $300 million, Company begun its adventure in the world of space industry. From the beginning, project was standing out due the enormous sized plane which was considered as a first stage of the designed launch system. It was like stretching in size Virgin White Knight carrying SpaceShipOne space plane, also designed by Burt Rutan. Paul Allen decided to buy two Boeing 747-400 to utilize engines, avionics, landing gear and minor parts for building prototype of Stratolaunch. Plane was designed with large wingspan at 117 m (largest wingspan plane ever produced) and twin fuselage. Between fuselages place and latches for second stage rocket were planned. For manufacturing of prototype, Allen and Rutan chose Scaled Composites, company founded by Rutan and owned by Northrop. Scaled Composites was also involved in manufacturing SpaceShipOne and White Knight, so was experienced Company with necessary potential for such ambitious project. At the beginning, until 2012, partner responsible for propulsion for the rocket was SpaceX. Next, after withdrawal of the SpaceX, Orbital ATK was considered as future partner. Positive which spoke in favor of Orbital ATK was their experience with two stage launch systems based on Pegasus rocket (about Pegasus rocket You can read here). First proposition from Orbital ATK was adopting Pegasus rocket, but carrier being under construction in Scaled Composites was able to lift larger rocket. It was started considering utilizing Pegasus II rocket, which was based on Pegasus and still was under development. Pegasus II was able to offer increased payload capability - up to 6100 kg for LEO missions which was impressive comparing to Pegasus which offered only 443 kg for LEO missions. For next three years Pegasus II evolved from combined solid and liquid fueled to all solid fueled rocket. Rocket was designed to utilize small wings and thrust vector control on first and second stage. Third stage was considered to be utilized with 5m payload fairing for LEO and 4 m fairing for GTO missions. Planned mass of the rocket was 210000 kg and comparing to mass of Pegasus (23500 kg) gives a picture of size of Pegasus II. Project started to take a shape. Stratolaunch, utilizing larger version of Pegasus, had ability to launch medium and heavy satellites into LEO with utilizing conventional runways for take-offs and landings. In 2014 situation changed and project started to be expanded to manned missions. It begun when Vulcan Inc. announced possibility of adopting smaller version of Dream Chaser space plane instead Pegasus II rocket. Dream Chaser was space plane project by Sierra Nevada Corporation (You can read more here) as response for NASA Commercial Orbital Transportation Services for lifting cargo and crew on atop Atlas V rocket. Combination of Stratolaunch and smaller (planned size reduction of 25%) Dream Chaser would be able to perform cargo/manned missions to ISS - this idea was interesting for both Vulcan Inc. and Sierra Nevada due the fact that both projects are in advanced phase of development and remain without any potential competition (Virgin is still oriented for space tourism than missions to ISS). On May, 2015 Vulcan Inc. announced about resignation from Orbital ATK as contractor. Pegasus II after adopting full solid fueled system was described as not meeting economical demands. As next contractor GenCorp (division of Aerojet Rocketdyne) was chosen. GenCorp RL10C-1 dual-motor liquid fuel engines are considered as propulsion for rocket stage of Stratolaunch vehicle. On August 2015, in the published interview, confirmed that lifting plane will take-off not earlier then in 2016:

"In 2016, I think, we’ll have the aircraft flying... we should have final assembly done the end of this year or early next year. For the next few years, we’ll do all of our test flights out of Mojave... "

It seemed that Company had stable plan of development, based on following positives of Stratolaunch. Firstly, it was offering 6100 kg of payload capability for LEO (unfortunately without any predictions about costs). Secondly, it could be part as commercial launch system for manned missions to ISS. First option was still based on assumption that the Stratolaunch project could be potential competition to expensive rockets launch systems. On 17 November 2015, Chuck Beames confirmed again that Company is considering strong changes in whole project, in spite of fact that still there is no clear vision of second stage of the launch system. It can be assumed that delay in program, lack of coherent vision of priorities (cargo or cargo and manned launch system) were responsible for slow development. Still, with almost finished lifting vehicle able to lift rocket or spaceplane, project is attractive if profitability would be maintained. Development of small satellites could be undermined the legitimacy of the program (as some sources claim) but still there is plenty of satellites which could not be "cubesatized"; also vision of lifting plane with space plane attached in daily missions should not be considered as a dream but as reality for couple years. Main problem of Stratolaunch are affordable prices of launch services offered on existing rocket launch vehicles with proven reliability (good example are prices offered by ISRO on their PSLV launch vehicle) and Virgin LauncherOne. Customers of Stratolaunch will probably pay a higher price at the beginning (not necessarily attractive, comparing to the launch service providers remaining on the market for a longer period of time) because of the need for return on investment for Vulcan Inc. Price factor would not be necessary significant positive of Stratolaunch. Considering Stratolaunch as regular vehicle for lifting satellites, we should remember that it is limited with its payload capacity. Customers interested in Stratolaunch, probably could not count on combined missions of couple spacecrafts for cost cutting like during conventional rocket missions. As LauncherOne by Virgin is considered - at the momentit seems to be more advanced construction, so it is also potential competitor in lifting satellites into LEO (LauncherOne designers focused more on second stage of their system, then on first stage which is adopted Boeing 747). Maybe best way at the moment for Stratolaunch is utilizing its potential with developed from scratched first stage combined with possibility of lifting space plane (Dream Chaser) for cargo/manned missions to ISS. It should be recalled, that Stratolaunch is commercial program without any grants from government agencies, so possibility of return on Stratolaunch is crucial factor which can decided if project will be continued. It is certain that Paul Allen was counting on government contracts after finishing project. As he stated in 2011:

"With government-funded spaceflight diminishing, there’s a much expanded opportunity for privately-funded efforts...Since the success of SpaceShipOne, I have thought a lot about how to take the next big step: a private orbital space platform business.”

The question should be if SpaceShipOne was good enough to be model for creating space launch system. SpaceShipOne was generally construction designed to fly one time and win the Ansari X prize; large launch vehicle system in such complicated configuration  like two-stage-to-orbit and horizontal take-off, horizontal landing will cost many times more and will bring many times more  problems to solve, then small, single use space plane. Government contracts are always welcomed, but getting such, depends on many factors. It is not obviously that such innovative launch system built by Company without any experience in space industry would be concerned as reliable solution for government agencies or military. But still, space exploration without variety of launch systems, available for small, medium and large companies and private customers is not possible; just like the creating global market was not possible without various means of transport, meeting different demands.

Sources:
https://en.wikipedia.org/wiki/Stratolaunch_Systems
https://en.wikipedia.org/wiki/Vulcan_Inc.
https://en.wikipedia.org/wiki/Pegasus_II_(rocket)
http://www.wsj.com/articles/microsoft-co-founders-space-project-is-in-limbo-1447809375
http://www.thespacereview.com/article/1994/1