On Thursday, May 19, 2016 at 9:01:47 AM UTC+12, wrote:
"A “Made in India” space shuttle may be on the horizon.

This month, the Indian Space Research Organization (ISRO)—India’s equivalent of
NASA—will begin the mission to launch its indigenous space shuttle, the Press
Trust of India reported on May 15.

Although the test model is about six times smaller than the actual version, the
launch will be a significant milestone in ISRO’s Reusable Launch Vehicle-
Technology Demonstration Program. The program, according to ISRO, is “a series of
technology demonstration missions that have been considered as a first step
towards realising a Two Stage To Orbit (TSTO) fully reusable vehicle.”"

See:

http://qz.com/684828/india-will-soon...utm_source=YPL

By using solid rocket boosters and a sled, along with an airbreathing engine on the first stage, they've needlessly increased development costs by a huge margin. Of course, if they wanted to develop these capabilities anyway, then, that's okay. If all they cared about was space access they'd take the Falcon route.

Now in a vacuum you must move at about 120 m/sec to reach an altitude of 70 km mentioned in the article. So that's the low end of the speed range. Since they're wanting to use a scramjet on the second stage, then they should be going Mach 0.8 or more. Mach 1 at Sea Level is 343 m/sec. So, this is likely the range of speeds the solid rocket boosters and sled achieve.

The interesting thing, is that a Maglev system could achieve these speeds far more efficiently without the bother of using solid rocket motors.

https://www.youtube.com/watch?v=OI_HFnNTfyU
https://www.youtube.com/watch?v=f5mA4l6xmGs

This is sufficient to achieve scramjet switchon.

https://info.aiaa.org/Regions/Wester...20Scramjet.pdf

http://arc.uta.edu/publications/td_f...berts%20MS.pdf

The averaged specific impulse of a scramjet engine from Mach 0.8 through Mach 10 is 3000 sec - the equivalent of 30 km/sec - with hydrogen only as fuel.

At one gee horizontal acceleration it takes 6,245 meters to achieve sound speed. At two gees4,417 meters to achieve sound speed. A 300 ton vehicle requires 2.94 MegaNewtons of force. Force times distance is energy, 18.36 GigaJoules. A 300 ton mass moving at 350 m/sec contains 18.36 Gigajoules - so this checks. V=a*t so V/a = t so 350 m/sec / 9.80655 m/s/s = 35.69 seconds. 18.36 GigaJoules / 35.69 seconds equals 514.4 MegaWatts of power.

Mach 10 is 3.43 km/sec. With an *effective* exhaust speed of 30.0 km/sec we require

u = 1 - 1 / exp( 3.43 / 30 ) = 0.1080 ~ 10.8%

propellant fraction. Applied to 300 tons requires 32.4 tons of hydrogen fuel.

Now a pure rocket with a 4.5 km/sec exhaust speed would require

u = 1 - 1 / exp( 3.43 / 4.5 ) = 0.53337 ~ 53.337%

So with a 4.3% structure fraction, which is typical these days we have 57.637% of the take of weight.


Structure fraction for a scramjet stage will likely be 14.2% - which adds a total of 25% of the take off weight. So, it is potentially lighter, despite the development costs.

So, of the 300 ton take off weight with scram jet stage we have;

32.4 tons of hydrogen fuel.
42.6 tons of structure.

75.0 tons - take off weight of first stage powered by scramjet.

The first stage moving at greater than 3 km/sec means that it will skip off the atmosphere like a Sanger aircraft, and fly back to the launch center after separation.

Meanwhile, there's an orbital stage that's pure rocket. It maasses 225 tons and is moving a 3.43 km/sec - so must have a delta vee of 5.77 km/sec. This requires a propellant fraction of 72.258% and so;

162.58 tons - propellant
9.78 tons - structure
52.64 tons - payload (8.10 tons hydrogen)

Which matches the Falcon Heavy.

Drone with GPS technology doesn't need radars and all the sensing stuff the Indians are talking about. However, if they think they need this as a military asset, this is a good cover for that development and might be worth the effort to them. Otherwise, they should be developig a simple space positioning system based on GPS - but that is vulnerable in a confiict to being turned off or disrupted.

The take off weight is equal to Boeing 747. The landing weight is equal to a 777. The payload is between a 777 and a 737.

Deployment of the payload on orbit and return of both stages to the launch center can occur within 180 minutes. 16 flights per day. Each flight requires 51.0 tons of hydrogen. 7,231.8 GigaJoules of energy. When added to the electrical load of 18.36 GJ per launch for the maglev track this is 7,250.2 Gigajoules of energy. Divided by 180 minutes this is 671.3 MW of electrical power. 514.4 MW is used for 35.6 seconds during launch, and the balance is used to produce liquid hydrogen and oxygen for the spacecraft - in the alloted time. Five spacecraft running continuously require 2,570 MW thorium power station surrounding the track. This puts up 175.5 tons per HOUR continuously. A space center that used low cost high value labour to produce aerospace assets at say $1,200 per kg would earn $210.6 million per hour. Transforming the Indian economy.