Tee hee...look at your own join date

Pete

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PJE

There's so much I don't know about astrophysics. I wish I had read that book by that wheelchair guy.

LOL. I've actually docked the ISS and the Shuttle on a few occasions (STS-108, STS-111, STS-113). As we say in the industry, "orbital mechanics is a *****." It takes ~3 days for the Shuttle to get to the ISS. Period. It's no different for Russian Soyuz or Progress vehicles.

Even if there were secret space stations, they'd have to be at an inclination of 51.6 degrees (like the ISS) to support Lear's theory - changing the inclination of a vehicle once in orbit is basically impossible. They'd have to be at different altitudes or the Shuttle couldn't use the same launch window for both. If they're at different altitudes, they'd be traveling at different speeds. If there were any truth to this, you could look up at the night sky and see one appearing to overtake the other.

But you can't. What are the odds that Coast to Coast wants to hear my reasoned explanation?

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Funnily enough, my first journey into space was a complete accident...

For real?
That's amazing!

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When you're standing on the edge of nowhere, there's only one way up...
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis
Rovers forever! - ToSeek

As we say in the industry, "orbital mechanics is a *****."

I assume that stands for "...harsh mistress."

It takes ~3 days for the Shuttle to get to the ISS. Period. It's no different for Russian Soyuz or Progress vehicles.

Direct ascent to rendezvous is theoretically possible, but only in the sense that it's theoretically possible to throw a ball bearing across the room and hit the light switch so as to turn it off. Because the passive vehicle's orbit is almost never harmonic with the ascending vehicle's position at launch along a rotating Earth, the launch windows would be excessively infrequent and narrow -- prohibitively so for any practical mission.

What are the odds that Coast to Coast wants to hear my reasoned explanation?

Probably about the same as the odds you could throw a ball bearing across the room and turn off the light switch with it.

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"Facts are stubborn things." --John Adams
Clavius Moon Base

Plus you've got to dock, not just knock the passive vehicle out of the sky! While it would be possible to intercept the ISS more quickly, traveling in any direction other than the same exact same velocity vector is the makings for very expensive space debris.

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Funnily enough, my first journey into space was a complete accident...

Plus you've got to dock, not just knock the passive vehicle out of the sky!

Exactly. Coincident points in space comprise only half the equation. You have first- and possibly second-derivative continuity constraints that translate to velocity and acceleration target values.

Continuing the ball-bearing analogy, if you're across the room throwing a ball bearing, some combination of velocity and arc that is dictated by the goal of getting the ball bearing from where you are all the way across the room to the light switch may not be compatible with the constraint of providing enough force to operate the switch but not too much so that you break the switch. If you have to throw that sucker hard in order to get it several meters away, it's going to break something when it hits.

Thus adds to the harsh mistressitude of orbital mechanics and the reason why ascent and rendezvous are done in phases.

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"Facts are stubborn things." --John Adams
Clavius Moon Base

For the planned manned missions to the moon, where they will do 2 launches, will it still take around 3 days for the second vehicle to rendevouz with the first?

As a ground controller or an astronaut? I assume the former, since there were other dockings for the ISS crews between 108 and 113, and since you clearly weren't part of the shuttle only crews for each of those three.

Just a ground controller *sigh* - I used to be an ADCO for the ISS.

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Funnily enough, my first journey into space was a complete accident...

For the planned manned missions to the moon, where they will do 2 launches, will it still take around 3 days for the second vehicle to rendevouz with the first?

I searched unsuccessfully for an answer from mission planning. My guess is that they will not take so long.

The ISS orbit is consistent with its overall mission as a long-term habitat for scientific and engineering research. While resupply mission rendezvous is obviously a constraint, it would have to be secondary since there's no way to plan an orbit favorable for all subsequent rendezvouses. Therefore the ascending vehicle has the burden to adapt its orbit, which requires the 3-day nominal harmonization period.

The initial launch of a second-generation Moon mission has one subsequent rendezvous as a primary mission constraint. Therefore its target orbit can be adjusted to make such a rendezvous more favorable for the ascending second launch, along with the additional constraints of orbital stability and compatibility with the planned translunar trajectory. You can plan both launches and orbits together as a single unit mission and adjust both to make the rendezvous as easy as it has to be.

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"Facts are stubborn things." --John Adams
Clavius Moon Base

Thanks. I wondered if a 3 day wait would cause a problem with, say, liquid hyrdogen boiling off.

It's okay, I still think your job is wicked cool.
(Yes, I have spent a lot of time in New England)

__________________
When you're standing on the edge of nowhere, there's only one way up...
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis
Rovers forever! - ToSeek

Agreed! (Besides, as anyone in any industry knows, it's the people in the trenches that do the real work --- the famous people just get all the credit)

Novelty alert: Google found one reference to "mistressitude" elsewhere on the web (it hasn't indexed this yet) and it found no references to "harsh mistressitude."

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I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

It's a perfectly cromulent word.

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"Facts are stubborn things." --John Adams
Clavius Moon Base

Maybe you were looking in the wrong places...

"Cromulent" is not in my dictionary.
I guess "harsh mistresstude" is like "That's frierd. It's freaky, and wierd."

__________________
When you're standing on the edge of nowhere, there's only one way up...
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis
Rovers forever! - ToSeek

If you can't find it in the dictionary, it's time to google it. In this case, it's also a hint about the joke that you can't find it in the dictionary. It's a Simpson's reference. From the urban dictionary:

Cromulent

Used in an ironical sense to mean legitimate, and therefore, in reality, spurious and not at all legitimate. Assumes common knowledge of the inherent Simpsons reference.

__________________
I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

I love this place! Conspiracy theory debunking and Simpsons references. Awesome!

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Funnily enough, my first journey into space was a complete accident...

...and don't forget the orbital mechanics tutorials!

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"Facts are stubborn things." --John Adams
Clavius Moon Base

That's not all! We've got Star Wars quotes and discussions of superheroes powers, too! BAUT is a really fun place!

__________________
When you're standing on the edge of nowhere, there's only one way up...
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis
Rovers forever! - ToSeek