Question General Spaceflight Q&A

[Urwumpe]

How many orbits does it realistically take for the shuttle to intercept the ISS?

It could do it in a pretty short time, depending on how close to the ISS it is launched. The final approach just takes four orbits, the orbit insertion takes two orbits, so you could minimal need six orbits for it.

But in reality, you have also other constraints that influence the flight plan:

• You need to do a OBSS survey of the heat shield.
• Your crew needs at least 36 hours for adapting to micro-gravity, otherwise you would have potentially space-sick astronauts during manual docking.
• The ground stations need to calculate the maneuvers that are not done by the on-board computer by radar data. Having more orbits for measurements means better accuracy.

 

[ElPelado]

White circles with black dots on the ISS

I think once someone asked what those white circles with black dots all around the station are, and someone said that those were points used to guide the robot-arm.... or something like that...

Can any one explain what those really are? and what's their use?
Thanks!

 

[Urwumpe]

I think once someone asked what those white circles with black dots all around the station are, and someone said that those were points used to guide the robot-arm.... or something like that...

Can any one explain what those really are? and what's their use?
Thanks!

They are reference marks for the automatic SSRMS motion. The control computer uses the dots for telling where the end-effector is and how to locate for example the next grapple fixture for walking over the skin of the space station (Grappling the new fixture on the hull, releasing the old fixture, make the base the new end effector...repeat until the robot arm is at the fixture that is planned to be used for the task).

The astronauts don't need to execute that themselves, the robot arm can do such basic tasks itself.

 

[DaveS]

They are reference marks for the automatic SSRMS motion. The control computer uses the dots for telling where the end-effector is and how to locate for example the next grapple fixture for walking over the skin of the space station (Grappling the new fixture on the hull, releasing the old fixture, make the base the new end effector...repeat until the robot arm is at the fixture that is planned to be used for the task).

The astronauts don't need to execute that themselves, the robot arm can do such basic tasks itself.

Actually, not correct. Those dots are part of the now defunct Canadian Advanced Space Vision System (ASVS): [ame="http://en.wikipedia.org/wiki/Advanced_Space_Vision_System"]Advanced Space Vision System - Wikipedia, the free encyclopedia[/ame]

 

[ElPelado]

Ok, thats what I asked. I remembered that it is used for automatic motion of the arm, but I didnt know that automatic motion was being used.

So, for example, yesterday, after the arm gave the shuttle arm the ELC-4 and moved to the truss, it was done automatically?

Thanks!

 

[Urwumpe]

Actually, not correct. Those dots are part of the now defunct Canadian Advanced Space Vision System (ASVS): Advanced Space Vision System - Wikipedia, the free encyclopedia

I had the dots explained as part of the robot arm control system. And not as defunct. After all, such dots are not mysterious experimental technology, but exist in more sophisticated ways already in industry, for example in car factories.

 

[DaveS]

I had the dots explained as part of the robot arm control system. And not as defunct. After all, such dots are not mysterious experimental technology, but exist in more sophisticated ways already in industry, for example in car factories.

Well, they aren't used any more on ISS. The MPLMs for example used to have them, but they have been removed. And there's none on the trusses or any of the pressurized modules beyond Destiny.

---------- Post added at 10:59 AM ---------- Previous post was at 10:52 AM ----------

Just to settle this I have asked ULF5 Lead Flight Royce Renfrew if the ASVS is used anymore on Twitter.

 

[Donamy]

At one point, it looked like the cross hairs in the ODS were centered on the dot, on the grapple pole of the PMA2. Maybe just a coincidence.

 

[DaveS]

Just got a reply from ULF5 Lead Flight on the ASVS "dots". According to him, they're not used anymore.

 

[Izack]

Is there a good source of information on the electrical systems of the ISS?

 

[Wishbone]

http://www.spaceref.com/iss/ - the only linky that currently comes to mind, specifically http://www.spaceref.com/iss/ops/iss.familiarization.pdf

I've got a Q, though. Are there any reports on the detailed inner workings of Data Management System and other main ISS GNC software?

 

[dnt462]

How is Mission Control set up, because i have a hard time imagining it runs a schedule like during Apollo were a flight could last up to 2 weeks?

 

[Wishbone]

MCC-Moscow is operating in shifts, 24 hours a day. Each organisation with a piece of the responsibility pie has its representatives in the control group. There is also a NASA support group that does shifts the same, and is the backup for MCC-Houston.

Their e-mail is [email protected]; the web site is less informative: http://www.mcc.rsa.ru/

MCC-M is a department within TsNIIMash, the head research institute of Roskosmos.

 

[ElPelado]

Small question: I've read many times that if the Main Engines keep going on until the ET is empty, they can explode or be damaged in some way... why is that? What exactly would happen?
Thanks

 

[garyw]

The turbopumps in the engines would overspeed and fly apart. Result would be very bad. this is why it's imperative that the various tank cut off sensors are working correctly.

 

[Urwumpe]

The turbopumps in the engines would overspeed and fly apart. Result would be very bad. this is why it's imperative that the various tank cut off sensors are working correctly.

Not just that, also you could overheat at the LOX pump to the point, that the metal of the engines starts to react and burn with the oxygen. Hydrogen-rich cutoffs are preferred because of that.

 

[IronRain]

I have a question about the forward docking mechanism of Zvezda. How was it attached to the hatch (because the only attachment point seems to be in the center and where is the docking mechanism now? (disposed or still on ISS...)

 

[Orbinaut Pete]

I have a question about the forward docking mechanism of Zvezda. How was it attached to the hatch (because the only attachment point seems to be in the center and where is the docking mechanism now? (disposed or still on ISS...)

The forward port of Zvezda uses the passive Hybrid docking system. The hatch itself includes a docking cone, as seen in the image below.

Once the docking to Zarya was completed, the hatch was removed. It currently resides in the Transfer Compartment of Zvezda (see image below), as it will still be needed when the MLM docks to Zevzda's Nadir port (as the hatch is completely removable from the forward port, it can also be used in the Zenith and Nadir ports of Zvezda).

Hi-res version.

 

[IronRain]

Thanks! Do they need to de-pressurize the hatch section or a special EVA to position the hatch? Something needs to be remove from the nadir hatch I guess?

 

[Orbinaut Pete]

Thanks! Do they need a special EVA to position the hatch? Something needs to be remove from the nadir hatch I guess?

For the Nadir hatch, they can just close it as normal before Pirs undocks from Zvezda. However, when there is negative pressure on the other side of the hatch (like in 2009 when they needed to put the docking cone in place ready for the MRM-2 docking to Zevzda Zenith), and "internal" EVA is required. In such a scenario, the crew suit up inside Zvezda's Transfer Compartment, close the hatches between the Transfer Compartment and the rest of the station, depressurise the Transfer Compartment, then remove a flat hatch and put the conical hatch in place of it.