Inflatable spacelift

[K. A. Pital]

A spacelift that inflates and lifts into space some equipment on it's spire.

Would that be plausible with any type of flexible material currently existing? Or aquirable in the near future? Carbon tubes?

[Surlethe]

To lift any meaningful amount of material into space, I would expect the pressure required to inflate the lift would be incredible. How would you pump the air into it?

[The Duchess of Zeon]

The only really viable way to use lifting gas for reaching orbit would be to have a giant, hydrogen filled dirigible attain an altitude above 100,000 feet and then launch an underslung rocket into LEO. Which would actually be very cheap.

[The Duchess of Zeon]

Say, we can do the launch over the equator with a dirigible designed to reach an altitude of 120,000ft (we need a dirigible because we want a powered lift vehicle so we can maintain a perfect alignment over the equator, and so we can protect the payload against unexpected events; power is so much more useful than drifting), so first we get the rocket to 120,000ft, and then we align it perfectly with the equator, and then launch. We can get about 1,500 metric tonnes of lift capacity out of a dirigible built with existing materials, which would have to be the maximum weight of the rocket; from 120,000ft, however, that offers a very good payload to orbit, and we'd want the highest possible thrust/weight ratio that modern science can give us on the rocket as well. We can even release it so that the rocket motor fires at the optimum angle for orbital entry.

[Sidewinder]

Three quarters of the atmosphere lies within the troposphere, and the depth of this layer varies between 17 km at the equator and 7 km at the poles. The ozone layer, which absorbs ultraviolet energy from the Sun, is located primarily in the stratosphere, at altitudes of 15 to 35 km. The Kármán line, located within the thermosphere at an altitude of 100 km, is commonly used to define the boundary between the Earth's atmosphere and outer space.

Altitude classifications
Low Earth Orbit (LEO) - Geocentric orbits ranging in altitude from 0 - 2000 km (0 - 1240 miles); one revolution takes 90 minutes, the speed is 8 km/s.
Medium Earth Orbit (MEO) - Geocentric orbits ranging in altitude from 2000 km - to just below geosynchronous orbit at 35,786 km (22,240 miles). Also known as an intermediate circular orbit.
Highly Elliptical Orbit (HEO) - Geocentric orbits with a high apogee and low perigee that result in long dwell times near apogee.
Geosynchronous Orbit (GEO) - Geocentric orbit with an altitude of 35,786 km (22,236 statute miles) above mean sea level. The period of the orbit coincides with the rotation period of the earth: 24 hours; the speed is 3 km/s.

Considering that the balloon in question must be rigid enough to NOT bend under the influence of gravity, water (condensed water vapor, rainfall, ice), or winds, the materials used must be incredibly strong, and therefore, incredibly expensive. Add the fact that HUGE quantities are needed to make a balloon big enough to lift something that high, and the budget would "balloon" to the point where it's more economical to simply build a hundred rockets.

How would you pump the air into it?

With jet engines? (Of course, it would require enough engines to power a bomber wing.)