# Is it possible to launch a satellite into orbit with a solar sail and a weather balloon using the magnetic poles?

At the poles the solar wind directly impinges. Suppose we put a solar sail satellite in a weather balloon at one of the poles. When it reaches the maximum altitude (~50km) it opens the solar sail and uses the solar wind to accelerate.

Is it possible for such a configuration to put something in orbit?

• "Its possible a such configuration put something in orbit?" No. The solar wind would not penetrate the atmosphere to any altitude to which a balloon could rise. – Andrew Thompson May 13 '16 at 18:41
• @AndrewThompson: You should probably make that an answer. – Nathan Tuggy May 13 '16 at 18:43
• @NathanTuggy Meh.. I don't quite think it has enough information to be a good answer, and BowlOfRed entered an answer that covered another important aspect that I neglected to mention. – Andrew Thompson May 13 '16 at 19:20

The problem is that you have to go from low-speed regime in the atmosphere (the balloon), to a high-speed regime out of the atmosphere (~7000m/s). The low forces available from a solar sail don't allow this to happen quickly enough.

At an intermediate speed it is either destroyed by forces from interacting with the atmosphere or it is insufficiently supported and falls back down.

My hope was not to have to get the high speed regime. Instead use the solar thrust to nullify and constant help the probe to get out the earth.

The problem is that solar thrust is very low, so you need a huge surface area to capture it. Let's say you had a 1kg payload in the upper atmosphere at low speed. Without a balloon, you need the sail to counteract the weight.

Unfortunately, the force available from light is low. Discounting all sail losses, it's about 8.25µN/m^2. If we imagine a magical solar sail that is massless, then to counter the payload weight it would have to be: $$A = \frac{W}{P}$$ $$A = \frac{9.7\text{N}}{8.25\frac{\text{µN}}{\text{m}^2}}$$ $$A = 1.1\text{km}^2$$

So a perfect, massless sail would still need to be over a square kilometer in size to counteract the weight of a kilogram. This is simply not practical for such a small payload. Add in the mass of sail and it becomes impossible. Adding in ionic pressure doesn't help significantly.

Only after you reach orbit (when weight no longer is a problem and tiny forces can do useful work) can such a low-thrust device be useful.

• My hope was not to have to get the high speed regime. Instead use the solar thrust to nullify and constant help the probe to get out the earth. – Esdras Caleb Jun 2 '16 at 13:29
• new idea propel the probe to out ionosphere with laser open the sail after this... Considering we are in pole we could use solar power to empower the laser and propel the probe for a long time util it reach the ionosfere or more. – Esdras Caleb Jun 9 '16 at 13:44
• @EsdrasCaleb, then you're basically using lasers to get to orbit. The sail doesn't help you before then. Lasers to orbit are an interesting possibility, but it's separate from sails and balloons. – BowlOfRed Jun 9 '16 at 15:43
• well we could use ballons to get at some poit and lases afther this point. A ballon could be an stage and the sail the final stage. – Esdras Caleb Jun 9 '16 at 15:50
• @EsdrasCaleb, yes, but launch from balloon only saves you about 1% of the launch energy. If you can just run the laser a bit longer, why bother with the expense and complexity of a balloon? For a traditional rocket it would save (some) fuel and therefore payload. For a laser launch, it only saves you a bit of time. – BowlOfRed Jun 9 '16 at 15:56

You need 1000km of altitude to break even between air drag and light pressure of sunlight. Below that the solar sail acts as a parachute, dragging against the remains of the atmosphere. You must reach 1000km altitude by other means. Definitely not a balloon, and not an orbital gun.

Also, solar wind (protons and ions) accounts for about 0.5% of "thrust" produced by the solar sail. It's the light (photons) that provides the bulk of its propulsive force, and it's not impeded by Earth's magnetic field, so the launch at a pole doesn't help in any significant way.

• Kudos for addressing my hare-brained supplement to the OP – called2voyage May 13 '16 at 21:42
• Yes, I gessed the north pole boreal winds would help has no need of a such high altitude, and the concentrated winds coming from the magnetic field wold help get more ions and protons in sail. But I don't have the data to say if this assumptions would be true... – Esdras Caleb Jun 2 '16 at 13:28