The thread for space cadets!

[warpus]

Yeah, I gotcha, I just still can't visualize this. Then again, I've never tried to put a satellite into geostationary orbit. It's just that what's been pounded into my head is that any burn in the retrograde lowers your orbit on the other side i.e. periapsis. Clearly that is just an oversimplification. I'm going to have to do this in KSP to see the exact effect of the burn to understand it I think.

Seems like this would be easier to do further out, i.e. not close to the planet. Isn't that where most geostationary satellites live? Is this maneuver even possible when your circular orbit is super close to the atmosphere, or will you just start dipping into the atmosphere eventually?

I have too many questions.

edit: I watched a video on how to put up a satellite into geostationary orbit and that's not how you do it. It seems that it has to go at a specific orbit. It also seems that your speed around a planet depends on your orbit height and nothing else. So how could it be possible to stay at the same orbit and slow down? I am even more confused now. But I do realize that orbital mechanics aren't easy to wrap your head around, so I'm probably just missing some key detail

 

[red_elk]

What's the best way to explain how that works? If you burn retrograde your periapsis will lower. If you burn away from the planet your apoapsis will increase in height. Do both of these actions balance out as you make your way around the planet? It's not easy to wrap your mind around.

I think they do, as long as you adjust thrust vector when your ship goes around the planet.

Even a small satellite takes a lot of thrust to get to geostationary orbits. But once there, the speed of the orbit balances the pull of gravity so they're stable(ish).

Technically, this applies to any circular orbit, not just geostationary
The only remarkable thing about geostationary orbit is that satellites on it have period of 24 hours.

 

[Cutlass]

Yeah, I gotcha, I just still can't visualize this. Then again, I've never tried to put a satellite into geostationary orbit. It's just that what's been pounded into my head is that any burn in the retrograde lowers your orbit on the other side i.e. periapsis. Clearly that is just an oversimplification. I'm going to have to do this in KSP to see the exact effect of the burn to understand it I think.

Seems like this would be easier to do further out, i.e. not close to the planet. Isn't that where most geostationary satellites live? Is this maneuver even possible when your circular orbit is super close to the atmosphere, or will you just start dipping into the atmosphere eventually?

I have too many questions.

edit: I watched a video on how to put up a satellite into geostationary orbit and that's not how you do it. It seems that it has to go at a specific orbit. It also seems that your speed around a planet depends on your orbit height and nothing else. So how could it be possible to stay at the same orbit and slow down? I am even more confused now. But I do realize that orbital mechanics aren't easy to wrap your head around, so I'm probably just missing some key detail

If you slow down, you'll start falling towards the planet. And without exerting a thrust to maintain altitude, will eventually hit air and burn up.

 

[Kaitzilla]

I'm not sure if the legendary Hobbs ever linked this, but I really liked this story.
http://www.astrodigital.org/space/stshorse.html

The Space Shuttle and the Horse's Rear End


Say friend, did you know that the US Standard railroad gauge (distance between the rails) is 4 feet, 8 1/2 inches.
That's an exceedingly odd number. Why was that gauge used?
Because that's the way they built them in England, and the US railroads were built by English expatriates.
I see, but why did the English build them like that?
Because the first railway lines were built by the same people who built the pre-railroad tramways, and that's the gauge they used.
Well, why did they use that gauge in England?
Because the people who built the tramways used the same jigs and tools that they used for building wagons, which used that wheel spacing.
Okay! Why did their wagons use that odd wheel spacing?
Because, if they tried to use any other spacing the wagon wheels would break on some of the old, long distance roads. Because that's the spacing of the old wheel ruts.
So who built these old rutted roads?
The first long distance roads in Europe were built by Imperial Rome for the benefit of their legions. The Roman roads have been used ever since.
And the ruts?
The original ruts, which everyone else had to match for fear of destroying their wagons, were first made by the wheels of Roman war chariots.
Since the chariots were made for or by Imperial Rome they were all alike in the matter of wheel spacing.
Thus, we have the answer to the original question.
The United States standard railroad gauge of 4 feet, 8 1/2 inches derives from the original specification for an Imperial Roman army war chariot.

And the motto of the story is Specifications and bureaucracies live forever.
So, the next time you are handed a specification and wonder what horse's ass came up with it, you may be exactly right.
Because the Imperial Roman chariots were made to be just wide enough to accommodate the back-ends of two war-horses.

So, just what does this have to do with the exploration of space?
Well, there's an interesting extension of the story about railroad gauge and horses' behinds.
When we see a Space Shuttle sitting on the launch pad, there are two big booster rockets attached to the sides of the main fuel tank.
These are the solid rocket boosters, or SRBs.
The SRBs are made by Thiokol at a factory in Utah.
The engineers who designed the SRBs might have preferred to make them a bit fatter, but the SRBs had to be shipped by train from the factory to the launch site.
The railroad from the factory runs through a tunnel in the mountains.
The SRBs had to fit through that tunnel.
The tunnel is slightly wider than a railroad track, and the railroad track is about as wide as two horses' behinds.

So a major design feature of what is arguably the world's most advanced transportation system was originally determined by the width of a horse's ass.

 

[Cutlass]

I have seen that before, although I forget where.

 

[Kaitzilla]

I have seen that before, although I forget where.

We did get some revenge against horses.

The space shuttled rated 37 million horsepower, which should make their whole race feel inadequate.

I can't throw too many stones at horses though for obvious reasons.

 

[r16]

has been argued against but ı wouldn't have a link ready and there have been so many railroad gauges .

 

[Berzerker]

Eta Aquarids peak tonight... We're nearing a full moon apparently so viewing might be best when the Moon sets around 4-6 am I guess. Its remnants of Halley's Comet we go through twice a year.

 

[Ferocitus]

Comet SWAN was visible from Adelaide early this morning.
Not one person predicted that it would prise the sheeted dead from the iron-hard ground.
So disappoint!

 

[Imaus]

We have a closer black hole neighbor, it seems. 1120-1210 odd LY away and the system is in is visible to the naked eye, if you're south of 33 degrees N.

 

[Lemon Merchant]

We have a closer black hole neighbor, it seems. 1120-1210 odd LY away and the system is in is visible to the naked eye, if you're south of 33 degrees N.

This is the very cool stuff that I like to see. I love this thread.

 

[Michkov]

Here is Jupiter in infrared

 

[Birdjaguar]

Virgin Galactic aims for Mach-speed travel

Adventurists around the world are now lining up for Virgin Galactic tourist flights into space, but in the near future, the company could also be rocketing people around the globe.

The company said in February that it wants to build a fleet of vehicles that could transport passengers from Los Angeles to Tokyo in just two hours, and from New York to London in one.

It’s already working on the technology at its headquarters at the Mojave Air and Space Port in California. That’s where The Spaceship Co., Virgin Galactic’s subsidiary, built the first VSS Unity passenger rocket and the VMS Eve mothership, which are both in New Mexico now doing test flights to prepare for commercial launch.

Once operational, Eve will carry the Unity on its underbelly to about 45,000 feet, at which point the spaceship detaches from the carrier plane and fires its motors to shoot into space at more than 50 miles up.

The Spaceship Co. is now building more rockets and motors to join the Unity and Eve in New Mexico. But alongside those efforts, it’s laying the groundwork for superfast Earth-bound planes, drawing in good part on the knowledge and technological advances achieved through 16 years of research and development of commercial spaceships.

Those plans got a boost last Tuesday, when Virgin Galactic announced a new Space Act Agreement with NASA to work together on the technology needed to facilitate development of high speed point-topoint travel.

The agreement, signed with the Langley Research Center, enables collaboration across all of NASA, the company said.

“This is the beginning of an important partnership for Virgin Galactic and The Spaceship Co. that will support the future development of aviation technology,” Virgin Galactic CEO George Whitesides said in a statement. “Virgin Galactic’s unique experience and innovative technology platform will, in partnership with the historic capabilities of NASA and other government agencies, enable the progression of new technical steps that will improve U.S. competitiveness. We see this as an area with tremendous growth potential that we will continue to invest in, alongside our commercial spaceflight operations.”

The company envisions a system that would be integrated into existing airspace and airport infrastructure to allow passengers to board superfast vehicles for point-to-point trips across the globe.

“It’s an exciting opportunity,” Whitesides told the Journal in March. “We’re working now on the fundamental pieces of high-speed global mobility.”

Chief Operating Officer Enrico Palermo said the company is building on lessons learned from its spaceship technology to “transform” planetary travel.

“We’ve been traveling around the planet for 50 years at basically the same speed, but we’re looking at technology now that can greatly increase those speeds to connect the world a lot more in the future,” Palermo told the Journal in March. “We’re well-poised to do it as the only team today that’s already designing, building and flying a vehicle at supersonic speed. We’ve built the team and the processes for it.”

The company formed a partnership in October with Boeing, whose venture capital arm HorizonX invested $20 million to help develop high-speed mobility. A focused project team and an advanced engineering group are now working on that mission in Mojave.

 

[Thorgalaeg]

Virgin Galactic aims for Mach-speed travel

In a world where amazing planes as the Concorde or the A380 are prematurely retired and airliner designers are thinking on plastic windowless pilotless aircraft to save some cents/seat, a rocket powered airliner doesn't look like an idea with a bright future.

 

[Birdjaguar]

In a world where amazing planes as the Concorde or the A380 are prematurely retired and airliner designers are thinking on plastic windowless pilotless aircraft to save some cents/seat, a rocket powered airliner doesn't look like an idea with a bright future.

False starts in new tech are common. The Concord was ahead of its time and too expensive for all but the rich. The new rocket powered planes may follow the Concord path, but faster travel is in our future. You can see it rail traffic in many places; just not in the US. The trick is to replicate the jump made in rail to air travel. We don't yet know what that solution will look like: Bigger planes? Smaller planes? Tiny planes? Public owned? Private? Rockets? Jets? Other? Faster trains running under the ocean?

 

[Berzerker]

Here is Jupiter in infrared

this may be just my imagination, but see those whiter (hotter) spots in that lowest dark band?

Isn't that about where comet Levy broke up and hit Jupiter?

 

[Berzerker]

 

[Michkov]

If you click through the link at the other end of the picture has a visual image of Jupiter taken around the same time for comparison. As far as I can tell the Shoemaker Levy crashsite is on the other side of the planet since there is no red spot to be seen. Also I the heat of the impact would by now be dissipated.

 

[hobbsyoyo]

Has there been naturally occurring antimatter detected?

Positrons are created on earth by cosmic rays and these naturally occurring Positrons were the first evidence for antimatter.

Also, sea quarks are about 30% of the mass of nucleons, so a significant fraction of all matter mass is actually antimatter quarks.

Beta particles can be positrons, so there is naturally occurring antimatter by way of atomic decay all the time as well.

We may have lost our resident rocket scientist but does anyone know why space ships dont burn up while leaving the atmosphere? Why cant a ship enter the atmosphere at about the same speed it leaves or is that an impossibility with our current technology?

Rockets do have to be protected against atmospheric heating during launch. The peak heating load can be on the order of 500 - 1500 W/m2 or something ridiculous like that. The trick is that the rocket is exposed to this only very briefly as it climbs out of the atmosphere very quickly. This allows them to get away with minimal thermal protection.

thats what I dont get, seems like we could have a ship expend fuel to slow down to roughly match the rotation of the Earth so the friction of entering doesn't burn the ship up. Maybe our fuel etc is just too 'primitive' at this point but it cant be long before we figure that out.

You would not really need to cancel the rotation of the Earth, that's kind of irrelevant to the rocket; you need to cancel the rockets forward velocity. If you were able to do that, the rocket would fall straight down to Earth. Depending on how high up you start from and what shape your rocket is, this could still cause you to have a ton of heating on the way down. A rocket with a huge surface area to weight ratio would fall more slowly - this is why Virgin Galactic's SpaceShipTwo opens up its tail fins during reentry as it stabilizes and helps to passively slow the rocket down.

But keep in mind that to fully cancel the rockets forward velocity, you'd need a rocket that is just as big as one to get to orbit, which would have to then be launched into space in the first place by a truly massive rocket. I believe @uppi said this in another post.

Virgin Galactic aims for Mach-speed travel

False starts in new tech are common. The Concord was ahead of its time and too expensive for all but the rich. The new rocket powered planes may follow the Concord path, but faster travel is in our future. You can see it rail traffic in many places; just not in the US. The trick is to replicate the jump made in rail to air travel. We don't yet know what that solution will look like: Bigger planes? Smaller planes? Tiny planes? Public owned? Private? Rockets? Jets? Other? Faster trains running under the ocean?

SpaceShipTwo could get your from Mojave to LA - maybe. It does not have a useful range for point-to-point travel without significant modifications. Given that they have been burning cash for over a decade with little to show for it and that Branson is selling a $400m stake in Virgin Galactic to float Virgin Atlantic, I don't see this coming to pass for a long time. They'd basically need an entirely new vehicle to do hypersonic point-to-point travel and they'd also have to figure out how to get around restrictions on sonic booms that would happen during climb-out and re-entry.

 

[tjs282]

Hobbs! You're back!