Using weather balloons pressurized to not to pop in a chain from the ground what is the highest altitude possible in a chain?

You could up scale to use blimps but it is a balloon that can achieve the highest altitude of 53km without a tether. Wind is not a factor in the model.

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I would use this to run a power line vertically or just make a ladder to sky dive from.

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    $\begingroup$ I think that you're giving too much information for this question. The question has nothing to do with this blimp/rail system. Your question appears solely to be "Could an electric turbine engine create enough lift to carry a heavy payload into space". So get rid of the stuff about the blimps. You are making it needlessly complicated. $\endgroup$
    – Phiteros
    Sep 9 '16 at 0:14
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    $\begingroup$ @Jen Useful references: en.wikipedia.org/wiki/Non-rocket_spacelaunch $\endgroup$
    – Antzi
    Sep 9 '16 at 1:34
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    $\begingroup$ Space launch is speed, not altitude. How fast can a electric turbine plane go? $\endgroup$ Sep 9 '16 at 3:05
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    $\begingroup$ @OrganicMarble: It's really both. Reaching orbital velocity at sea level won't get you very far. $\endgroup$
    Sep 9 '16 at 14:59
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    $\begingroup$ @jen I don't think any electric airplane has reached even a small fraction of that speed. $\endgroup$ Sep 9 '16 at 15:12

Summary: No, this won't work in any way, shape or form. And if you did get it to work, it'd be more expensive than using rockets.

10 reasons it won't work:

Aircraft can get to an altitude of ~30 km. Above that, the atmosphere is so thin you need unfeasibly large wings to provide enough lift. An aircraft that flies next to a rail is no different in this regard.

Then there's the method for transferring power from the rail to the aircraft. This has been studied extensively: trains use the same method to transfer power from their overhead catenary wires. At a speed of 500 km/h this is already problematic, as the SNCF found when preparing for the world speed record with their TGV. The pantograph presses against the power wire/rail. This moves the power wire/rail. At low speed, this movement is small enough that the pantograph remains in constant contact with the wire.

At high speed, the pantograph can't follow the wire reliably anymore so you get intermittent contact. Applying more (mechanical) tension to the wire reduces how much the wire moves around, but this is limited by the mechanical strength of the wire. The highest speed ever achieved with such a power transfer method is ~580 km/h or about 200 m/s.

Then there's the distance between the aircraft and the rail. This has to be small enough to allow a structure like a pantograph to bridge the gap. But it has to be large enough to prevent the aircraft from hitting the rail when it encounters turbulence (which can easily displace the aircraft tens of meters).

Even if you can overcome the turbulence problem, you've carried your rocket to 20 km altitude and 200 m/s. You need 200 km and 8 km/s, so all that effort has given a very small reduction of the rocket size.

Airplane-launched rockets exist (Pegasus, Virgin LauncherOne) but they aren't common. Most rocket companies don't think it's worth bothering with an aircraft as the first stage. An electric-powered aircraft would add several more hurdles to an already difficult problem.

It seems you're trying to make the launch cheaper by saving fuel. But the fuel cost is a negligible part of the cost of a rocket. A SpaceX Falcon 9 costs \$60M to launch. Only \$200k of that is the fuel cost.

Even if you could accelerate to 1000 m/s on your launch system, that leaves 7000 m/s that must be provided by the booster. 7/8 of a Falcon 9 is still a \$60M rocket, it'll just be a bit shorter than the current F9 because it needs less fuel. The only cost advantage is in a barrel section for the fuel tanks you can omit, and those are cheap parts.

So in order to save a few hundred thousand per launch, you're proposing a rail system and dozens of blimps. Launch rates would have to be huge to make that economically feasible. Until then, using an aircraft as the first stage is a better option, and even that has its limitations, as no aircraft exist that are large enough to launch e.g. a 4-ton communications satellite into GEO.

New: cost, wight, volume calculation

Catenary wire as used by railroads weighs on the order of 600 kg/km.

Bu60-1 was 60,000 m3, that's 50 m in diameter and had a payload of 4.6 kg. So a balloon capable of supporting 500 kg would need a volume of ~60 million m3, that's a diameter of 500 m.

The largest high-altitude balloon is 0.5 million m3 and has a lifetime of 30 days.

So your balloons would need to be 10 times larger than the largest high-altitude balloon ever made, and you'd need to replace them every 30 days.

The string needs to be at a shallow angle to prevent the aircraft from stalling. Say a 1/10 grade. To reach 50 km altitude, you need a string 500 km long.

  • A catenary 500 km long doesn't work: railroad catenaries are supplied with power at regular intervals, at 500 km the voltage drop would be severe.
  • to fill the balloons, you need 3 billion m3 of helium, that's 30 times the world annual production. Cost is on the order of billions of dollars.
  • I've ignored wind effects: high altitude wind exerts lots of force on the balloons and the wire.
  • $\begingroup$ You are kind of edging into the land of unobtanium with this laser filamentation stuff. If you can make up any technology you need, any system is possible. And, no matter what you do to the rail/balloon system, a turbine aircraft will not get you enough velocity to make it worthwhile. $\endgroup$ Sep 9 '16 at 15:23
  • $\begingroup$ My answer doesn't change. The big problem is the power transfer between the rail and the spacecraft, which limits the speed of your electric-powered stage to 200 m/s, making this stage pointless. $\endgroup$
    – Hobbes
    Feb 20 '17 at 14:00
  • $\begingroup$ The goal isn't to get to orbital speeds only a high atmospheric launch. $\endgroup$
    – Muze
    Nov 5 '17 at 20:45
  • $\begingroup$ question is better, but the answer doesn't change. I've added more detail. $\endgroup$
    – Hobbes
    Jan 31 '18 at 21:16

The velocity you need to maintain LEO (~200 km) is on the order of 7800 m/s (~28,000 mph).

The SR-71, which AFAIK is the fastest-flying jet aircraft, reached a top speed of a little over Mach 3, or around 1029 m/s (~2300 mph).

The X-15 rocket plane topped out at ~2020 m/s (~4520 mph). Both of these fell well short of what is required to reach orbit (which is what I interpret most people to mean when they say "space").

And, of course, you run out of usable atmosphere to generate lift well short of LEO.

So, yes, you definitely need rockets to actually reach orbit, meaning you need to carry the mass of the rocket engine and propellant with you as you climb the cable.

Then we have to consider the following logistical issues:

  • Stringing a series of blimps together from ground level to into the stratosphere (20-some-odd kilometers, give or take), such that they stay put and don't pose a hazard to other aircraft;

  • Suspending a continuous conductor from those blimps (that, at 20-some-odd kilometers long, is going to weigh several tens of tonnes, meaning that it will have to have a high tensile strength);

  • Keeping the string of blimps and conductor stable as an aircraft is screaming alongside it, and building it to withstand the shockwaves from the aircraft as it goes supersonic;

  • Transferring energy from the conductor to the aircraft;

  • Building an electric turbofan capable of propelling an aircraft to speeds in excess of 2000 m/s, while it's carrying the payload and rocket mass;

  • Safety protocols if a blimp envelope fails, or if the conductor breaks loose;

Then there are some engineering questions I'm in no way qualified to answer, like how thick the conductor needs to be to transfer sufficient power without melting, how to generate that power, how much is lost to resistance by the time you get to the top of the conductor, etc.

In short, this is not a practical approach.


Anything that saves you gravity losses is a good idea, which is why some people have developed airborne launch systems - the rocket isn't fighting gravity for as long as it would when launched from the ground, which does save quite a bit of propellant mass. However, airborne launch simply isn't practical for anything but small payloads. It's a lot easier (at least from an engineering perspective) to build bigger rockets than to build bigger airplanes.

  • $\begingroup$ @Muze: Altitude is a tiny part of the equation. The engineering complexity of this approach, coupled with power engineering requirements, will not make this any easier or cheaper than rockets. $\endgroup$
    – John Bode
    Nov 5 '17 at 22:06
  • $\begingroup$ @Muze: All of the issues I identified above will still be issues - how heavy is the conductor going to be, how are you going to transmit electricity along its length, what kind of resistance losses will you encounter, how will you insure it doesn't pose a hazard to other aircraft, how are you going to deal with shock waves once the vehicle goes supersonic, can you build an electric turbofan capable of reaching the necessary velocity, etc. $\endgroup$
    – John Bode
    Jan 16 '18 at 23:16
  • $\begingroup$ question revised. $\endgroup$
    – Muze
    Jan 31 '18 at 20:59

It looks like the space shuttle is doing 1500 m/s at 30km altitude, which is about 3350 mph. The fastest jet engine ever built is the mighty J-58 which in the SR-71 produces a top speed of about 2200 mph. I doubt that an e-fan can outdo that and it's already 50% short. You need to be going at least 15,000 mph to make orbit, so I don't see the e-fans adding any value.

  • $\begingroup$ Unless someone comes up with a scheme for very high wattage beamed power, this is a total non-starter. $\endgroup$
    – zeta-band
    Jan 17 '18 at 17:08

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