# Can modified solar sail use Earth's atmosphere to correct an eccentric orbit?

A solar sail power satellite used create thrust as a while in orbit around Earth will gain eccentricity because it can only propel from on side of the Earth. When the orbit will become eccentric enough the orbit will near the atmosphere.

Can lift be created by using a hard flat wing shaped sail instead of a conventional solar sail to use the ideal gas from Earth's outer atmosphere to gain altitude also correcting eccentricity to create an eccentric but stable orbit only using solar power?

Enough speed is needed to traverse the atmospheric drag of the Earth. For a tighter orbit enough solar sail surface area with weight would be needed compared to traditional solar sails. There be enough speed to allow the sail to use the drag to return the satellite on a mirror trajectory back past the Moon. But ideally the sail would not need to air break that the angle to the sun during a longer rang orbit would be self correcting. Vains would serve as both solar panels and a active orbital stabilization.

Can orbital maneuvers be performed by a solar sail to correct eccentricity?

Can a satellite work like a radiometer?

Can a solar sail be added to an ion engine and work better?

• It is preferred if you can post separate questions instead of combining your questions into one. That way, it helps the people answering your question and also others hunting for at least one of your questions. Thanks! Commented May 15, 2018 at 16:53
• I personally think that "Can the angle of the sail also help keep a periapsis orbit?" and "Can lift be created by using a hard flat sail instead of a conventional solar sail for planing the atmospheric pressure?" are seperate questions Commented May 15, 2018 at 16:59
• @JavaScriptCoder I split the questions
– Muze
Commented May 15, 2018 at 17:13
• To lift an orbit you need to add energy. But drag caused by the atmosphere consumes orbital energy and lowers the orbit. A wing may cause lift but not without drag.
– Uwe
Commented Jun 17, 2018 at 15:55
• @Uwe your are correct that inertia is gathered from the sun and then used in the maneuver leaving the satesail at the same speed and trajectory. So instead of using fuel every so often to maintain orbit it air brakes as it nears enough Earth every so often..
– Muze
Commented Jun 18, 2018 at 2:17

Apparently this question was edited while I was answering it. To the question, "Can you generate lift?": in a word, no. For two main reasons.

First, lift as we know it, and as codified in the classical lift equation, is generated in a collisional gas, i.e. the average distance between molecular collisions ("mean free path") is much smaller than the dimensions of the object generating the lift. This is not true at orbital altitudes. (See the discussion in David Hammen's answer to "Why are LEO satellites not aerodynamically shaped?") Due to the absence of molecular collisions the molecules traveling "over" the "wing" cannot have their paths deviated to follow the contour of the wing as the traditional Navier-Stokes approach to the flow would suggest. So the classical lift equation can't be used.

With the classical lift mechanism invalidated, the only other potential source of lift is molecular deflection, where incoming molecules collide with the surface of the object and reflect ("bounce off") that surface in a quasi-specular manner, resulting in a net momentum exchange that produces a force. But to get that force you need the quasi-specular reflection, at least to some degree, and this is tied to the "Accommodation Coefficient" that has been in the theoretical and laboratory literature since the 1930's, and in tests in space since the 1960's. Work by Kenneth and Mildred Moe indicate that measurements of the Accommodation Coefficient are consistent with entirely diffuse and low-velocity post-collision molecular trajectories, suggesting a large fraction of the molecules adsorb onto the surface and then are re-emitted: no specular reflection, so no deflection force.

That said, you can get some force component from the re-emission. But the re-emission speeds are at the thermal speeds for the temperature of the surface, and those are much slower than orbital speed. So the force derived from the re-emission is much less than the drag force, and L/D is so small it is worthless.

By the way, the research on atmospheric drag in orbit quoted above indicates that in very low Earth orbit there is some variation in the drag coefficient (and thus the Accommodation Coefficient) with vehicle shape, but above that it appears to be independent of vehicle shape. So it wouldn't matter much whether the solar sails were thin-film or rigid.

• @Muze I can't figure out the meaning of "...help keep a periapsis orbit create..." so I can't answer. Commented May 15, 2018 at 18:16
• "...proposition from the solar wind..." There is no solar wind inside Earth's magnetopause to formulate a proposition. Did you mean "propulsion from solar light pressure."??? If so, realize that it matters what you write. Before posting a question or comment, please be sure that what you write accurately reflects what you're thinking. This will prevent a lot of wasted time on the part of people trying to answer. Commented May 15, 2018 at 18:32
• yes you are correct. is that a chemical compound model rocket in your profile picture?
– Muze
Commented Dec 28, 2018 at 12:20
• @Muze Yes, but it's unique. In the mid-1970's I converted a single-stage Estes 1/100-scale Saturn V to a 3-stage (flying) model, using a combination of Estes D and C engines, with the stage separations in the scale locations. The 2nd and 3rd stages are ignited electrically. WIth the masses of the photoflash batteries in the Apollo CM and the D and C engines in the S-II and the S-IVB, it didn't need those clear plastic fins the single-stage version used for aerodynamic stability. I haven't flown it for a long time! Commented Dec 28, 2018 at 20:41
• What was its maximum altitude?
– Muze
Commented Dec 28, 2018 at 20:43

The newly-edited question states "When using a solar sail to create thrust while in orbit around Earth the orbit gains eccentricity. When the orbit becomes eccentric the orbit nears the atmosphere." If the orbit's semimajor axis a remains fixed, then increasing eccentricity indeed drives down the periapsis radius.

But application of a force component in the direction of the velocity vector will work to increase a. Force applied at apoapsis will work against drag to increase the periapsis radius. Drag up there is extremely small, so to prevent the periapsis radius from increasing, the solar sail orientation would have to be managed carefully to keep the resulting forces small, both along the velocity vector and perpendicular to it. Forces applied at periapsis along the velocity vector raise or lower apoapsis: anti-parallel forces, such as drag, lower the apoapsis, while parallel forces, such as those from a properly oriented solar sail, raise apoapsis. Since drag is highest at periapsis, maintaining the apoapsis radius is where the solar sail would be most helpful.

The requirement to maintain the apoapsis radius drives the size of solar sail needed to overcome periapsis drag. This is why at apoapsis the sail orientation must be managed carefully. The sail is capable of producing forces far larger than needed for periapsis radius maintenance. Incompetent handling of the sail orientation could cause large changes in that periapsis radius. If that change is downward, this could be trouble.