Is it possible to complete 1 orbit within the atmosphere?

[SpaceLaunchSystem]

I know it's probably not (because of atmospheric drag) but is there any velocity where you could complete an orbit within the atmosphere?

[SargeRho]

Define "within the atmosphere". The ISS is still in Earth's atmosphere. If by within the Atmosphere you mean below the Karman line, I think not.

[Motokid600]

"In the atmosphere" ... Yes, lol. Your velocity doesn't have much to do with it. It's the altitude you want. Because... Technically the ISS is still somewhat "in the atmosphere" So.. it depends how low are we talking here?

[SpaceLaunchSystem]

I mean below the karman line.

[Bill Phil]

Maybe if you had wings that are ginormous and still applied thrust. Not to mention that you need to change your attitude constantly....

[Dodgey]

According to Wikipedia the lowest possible orbit of one revolution is approximately 150km. So no you cannot, unless you had an immensely dense material.

[SpaceLaunchSystem]

According to Wikipedia the lowest possible orbit of one revolution is approximately 150km. So no you cannot, unless you had an immensely dense material.

Okay. Thank you for teaching me something new.

[Mazon Del]

I choose to declare that the first "orbit" was in fact completed by Magellan with the lowest altitude of roughly 10 feet above sea level (depends on where he was on his ship at any point). Check mate.

[SargeRho]

That's not an orbit though.

[sal_vager]

It's looking like the answer to this one is "no"

[zxczxczbfg]

Rule of thumb: It's not an orbit if you have to keep firing your thrusters to keep it from falling.

[PakledHostage]

I choose to declare that the first "orbit" was in fact completed by Magellan with the lowest altitude of roughly 10 feet above sea level (depends on where he was on his ship at any point). Check mate.

Or, you should say, some of his crew aboard the Victoria were the first to "orbit" the Earth. Nao Victoria was the only ship in Magellan's initial fleet of 5 ships to completely circumnavigate the Earth. Magellan himself was killed in a battle in the Philippines during the expedition.

Rule of thumb: It's not an orbit if you have to keep firing your thrusters to keep it from falling.

Magellan's crew didn't have to fire their thrusters to keep from falling...

[zxczxczbfg]

Magellan's crew didn't have to fire their thrusters to keep from falling...

Which is why his crew aren't considered the first people in orbit.

EDIT: Yes, I realize you're joking.

Edited November 5, 2014 by zxczxczbfg

[PakledHostage]

You do realise that Mazon Del and I are joking, right?

[Mr Shifty]

You might be able to complete an unpowered skipping orbit that skips below the Karman line.

[BagelRabbit]

The closest I can think of to this was a concept posed by Wernher von Braun. This was an absolutely ingenious way to return from the Moon.

After the astronauts lifted off the Moon, they would burn to a trajectory with the periapsis inside the Earth's atmosphere, but not by much. The astronauts would detach their top stage, which was designed like a plane, prior to entering the atmosphere. The trajectory that the astronauts took would have been shallow enough for the plane to leave the atmosphere. However, the plane would use its wings to brute-force itself to remain at altitude. Once the plane had burned off most of its velocity (which would take almost a full "orbit" to complete), it would glide in for a landing.

This would reduce the G-forces on the astronauts tremendously: Wernher calculated that the astronauts would experience 2 g's of centripetal force, which would balance nicely with the 1g of gravitational pull, to give the astronauts about 1g of force. When the G-force dropped back to zero, the astronauts knew that they were at suborbital velocity, and that they could land. There were some little things that weren't entirely correct, there, but the overall concept was actually very clever.

I'm pretty sure that this is the closest we're gonna get to a full orbit in-atmosphere.

[HarvesteR]

I think the basic criteria for being officially in an orbital trajectory is that your spacecraft should be able to simply 'coast' its way entirely around the planet. No thrust applied by the spacecraft. Decay from external perturbations wouldn't void this criteria unless the forces are strong enough to cause a free-falling body to decelerate quickly enough that it doesn't manage to complete a single revolution, something very much like what being inside the atmosphere would do to you.

If you can manage to establish an orbit just inside the very edge of the cut-off point to Kerbin's atmosphere (around 69,750m altitude), you might be able to complete a full revolution before that tiny amount of atmosphere slows you down into a sub-orbital state again. That would be quite tricky, as even the lowest edge of the atmosphere still exerts some drag... Not sure if enough to decelerate you down into the no-return altitudes over the 30 minutes or so it takes to go around Kerbin, but as you lose altitude (and you will), the drag also increases, which lowers your periapsis yet more...

Actually, I'd love to see someone try... Now I'm intrigued.

Cheers

Edited November 5, 2014 by HarvesteR

[Bill Phil]

According to Wikipedia the lowest possible orbit of one revolution is approximately 150km. So no you cannot, unless you had an immensely dense material.

Like, say, a rod from a god? (Tungsten,low drag design)

[Mr Shifty]

If you can manage to establish an orbit just inside the very edge of the cut-off point to Kerbin's atmosphere (around 69,750m altitude), you might be able to complete a full revolution before that tiny amount of atmosphere slows you down into a sub-orbital state again. That would be quite tricky, as even the lowest edge of the atmosphere still exerts some drag... Not sure if enough to decelerate you down into the no-return altitudes over the 30 minutes or so it takes to go around Kerbin, but as you lose altitude (and you will), the drag also increases, which lowers your periapsis yet more...

HarvesteR! It would be interesting to see an attempt. The issue is that your initial orbital speed here is pretty fixed: an orbit at 69km has a speed of 2297 m/s. It should be pretty easy to see if it can be done. I suspect that good aerodynamics, you might be able use aerodynamic surfaces to stay inside the atmosphere at much higher speeds as in this video from the KSC to Wideawake Orbiter challenge. This might make it more likely to succeed.

ROgKCxozau4

[Tex_NL]

Rule of thumb: It's not an orbit if you have to keep firing your thrusters to keep it from falling.

So you're saying the ISS is not actually in orbit?

No one will dispute the ISS is well above the Karman line and in orbit. Still it experiences enough atmospheric drag to require frequents boosts to maintain altitude. The drag effect is significant enough to feather the solar panels on the dark side to conserve speed.

[tg626]

Atmospheric Studies
Kerbal Space Center, Kerbin 626
Dr. Wernher Von Kerman, Director
Gene Kerman, Mission Control

DATE: 141/01
TEST VEHICLE: K2

MISSION PROFILE: Launch a K2 rocket into a 68km orbit and observe, through ground tracking and telemetry, the 
duration and trajectory of it's subsequent ballistic flight.  Observations to reveal data about the properties of Kerbin's 
extreme upper atmosphere just below the Kerman Line.

SUMMARY: Vehicle was successfully launched and briefly established a 68.4km x 68.1km orbit, a testament to our 
engineers ingenuity and the new AR-202 Flight Control Computer.  Following this all active control was suspended 
and the vehicle was passively observed.  Vehicle began to tumble at a rate of approximately .8 RPM however it 
remained aloft and after 1 complete trip around the planet had only descended 10km.  Of course increasing atmospheric 
density resulted in an exponential loss of velocity and the attendant loss of altitude resulting in ground impact before
a second circumnavigation was completed.

Our staff will continue to analyze the detailed data from this mission in order to improve our understanding of 
Kerbin's uppermost atmosphere.

DBNR

Edited November 5, 2014 by tg626

[Javster]

You mean with no external power right?

[metaphor]

I've also tried this in KSP before, it seems an average rocket can go about 1.5 revolutions around the planet before landing when starting at a 69 km circular orbit.

[Tommygun]

I think this is one of those areas where defining the exact criteria may not be possible, but is left to a general group consensus.

There have been a couple of nonstop aircraft flights and balloon trips that some may argue as technically orbits too.

[WestAir]

Does this count if only part of your orbit is below the Karman line?