Forum: Civil and General Aviation

Elite 1K Joined: May 26, 2005 - 08:39 PM Posts: 1496

Orbital manuvering is HARD. I always knew that in the back of my head, but I started playing around with Orbiter http://www.medphys.ucl.ac.uk/~martins/orbit/orbit.html which is a free space simulator, and docking with another object in space will about drive you mad!

Big props to CDR Collins on a job well done!

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Do all space shuttle crew people get a USAF rank? Or is that within NASA itself?

No, they retain the rank that they held in their respective service upon entry into NASA. You can see in some of the pictures a mix of both Navy and Air Force wings. The civilian Astronauts don't hold a military rank. (I think)

Cool topic. The pics in the previous page are not of a real space shuttle. That's the Enterprise prototype (care to guess on how it got the name?), used to test glide performance, hence it is being released in flight. The small winglets on the back of the 747 were added because the shuttle blocks the vertical stabilizer.

Speaking of orbital maneuvering, anybody care to guess how astronauts turn in space (without propellants), why payloads are spun out of the shuttle’s bay, or why boosters are needed when instruments are turned on?

Last edited by agilefalcon16 on Aug 13, 2005 - 06:57 PM; edited 1 time in total

Pat1 wrote:

Cool topic. The pics in the previous page are not of a real space shuttle. That's the Enterprise prototype (care to guess on how it got the name?), used to test glide performance, hence it is being released in flight. The small winglets on the back of the 747 were added because the shuttle blocks the vertical stabilizer.

Yes, I'm aware that a few of the photos I posted on the previous page are of the Enterprise prototype, but I'm confident though, that they're not all of the prototype. Even though I can't prove it (Because the names are too small to read) I have found other photos that are of operational shuttles "piggybacking" on NASA 747s.

Shuttle Columbia

Shuttle Atlantis

Elite 1K Joined: May 26, 2005 - 08:39 PM Posts: 1496

They use reaction wheels to change attitude without burning RCS propellants, which are basically torquable gyros that can be spun up or slowed down to provide fine control.

Satellites are spun to better average out the center of mass so the satellite is more stable and makes it easier to calculate trajectories.

Not sure about boosters when instruments are turned on, the Shuttle is powered by fuel cells that don't generate any forces when operating.

Hi Guysmiley,

Thanks, I had no idea reaction wheels were used in spacesuits. Simple maneuvers like 180 degree turns can be performed by arm motions, just like one would do in a swimming-pool. In this case you would be “upside down” with respect to the previous position. Other turns can be performed with appropriate arm movements.

I’m not sure what you mean with “average out the center of mass”. I’m pretty sure ejected payloads are spun around an axis through the center of mass (or as close as possible to avoid other motions). Like you said, it is for stability purposes. Same principles at play; if you spin it before propelling it, it makes it less susceptible to torques and the orientation isn’t affected as much.

In the case with Voyager 2, boosters were turned on not to power up instrumentation. A lot of equipment uses spinning mechanisms (hard drives, recorders…) and like in the earlier cases, conservation of angular momentum requires the vessel to spin in the opposite direction (like a helicopter without the rear rotor). Boosters were turned on to counteract induced torques. Other schemes could also be used to counteract these torques.

Hi agilefalcon16,

Sorry I didn’t notice, I guess only the pics with the 747 in the silver scheme is porting the Enterprise?

Pat1 wrote:

why boosters are needed when instruments are turned on?

Is it because some instruments have gyros in them, and the boosters are needed to keep the shuttle from spinning around the gyro when it starts up? It wouldn't go much, but the whole "every action has an equal and opposite reaction" thing must still apply...

VPRGUY wrote:

Pat1 wrote:

why boosters are needed when instruments are turned on?

Is it because some instruments have gyros in them, and the boosters are needed to keep the shuttle from spinning around the gyro when it starts up? It wouldn't go much, but the whole "every action has an equal and opposite reaction" thing must still apply...

Hi VPRGUY,

Correct, a lot of satellites (if not all) have gyros as part of their inertial guidance system. They are set in motion before release (e.g. the spinning launch). Other equipment such has computer hardrives or tape recorders will induce moments which are corrected by IGS by boosting. And it is not just onboard equipment that will change the orientation, friction from upper atmosphere or even solar wind can induce torques!

Another way would be to turn on the same equipment in opposite places and opposite orientation (i.e. one facing inward and one outward) about the rotational axis.

Elite 1K Joined: May 26, 2005 - 08:39 PM Posts: 1496

Ah, I didn't realise you meant ASTRONAUTS, not spacecraft. Well, you could think of human arms as reaction wheels... sort of. Wink

Quote:

Well, you could think of human arms as reaction wheels... sort of.

Why not? Serves the same purpose...

saw that 747 up close and personal at an airshow.. ehres my budy coming out of it.

I thought you folks might enjoy looking at this old photo I took during one of my last F4 Tow Target Missions over the Lake Bed in California (near Edwards AFB).

It was when the 747 was being used to Piggy Back the Shuttle to Edwards (in-flight testing and avionics work was being conducted).

I always though I was very lucky to have been flying that day and had my camera with me to take the photo. I feel it is a historic shot....if you ask me Smile

My girlfriend took this picture when the 747/shuttle stopped at Altus, where she is stationed, for gas.

Very, very nice shot...what a great angle too...tell her ...great job!

Forum: Civil and General Aviation

What's up with the Shuttle?