Question Shuttle Launch in Orbiter versus NASA

[PaulG]

Ok, so how does NASA do it? They launch the shuttle, get into orbit, and they are pretty close to the ISS.

I've read the tutorials that talk about using Launch MFD, Align MFD, etc to get into the right orbit at the right time. But, its a manual launch and one little messup and I'll be out of fuel.

So, is there an autopilot to get the shuttle into orbit and close to the ISS? I mean, its all predictable, thats how NASA can get the exact minute of intersection right?

Thanks,
Paul

 

[SiberianTiger]

So, is there an autopilot to get the shuttle into orbit and close to the ISS? I mean, its all predictable, thats how NASA can get the exact minute of intersection right?

They use a bunch of eggheads with logarithmic scales. Oh wait, it's been a while since then...

 

[n122vu]

If you are looking to get as close to the way NASA does it as currently possible with Orbiter, I would recommend going to www.orbithangar.com Search for Shuttle Fleet by david413 or Space Shuttle Ultra. Unlke the default Atlantis, these have an autopilot integrated into their functionality. Plus, you can find scenarios for many real-world missions based on actual orbital data (STS-126 for example, which wrapped up on Sunday).

As far as how NASA does it (this is just a high-level answer), the shuttle's ascent is computer-controlled. Once in orbit, the orbiter must make necessary course correction and alignment burns to intercept the ISS (usually takes 1-2 days to intercept, I believe). Orbiter crew also performs RMS checkout, checks for damage to the orbiter during launch with the OBSS, etc., all of which can be simulated with these addons. (Not familiar with SSUltra, but documentation in Shuttle Fleet is very detailed regarding RMS operations).

Hope this helps.

 

[Urwumpe]

Well, real operations are just more careful.

When you do one simulation run in Orbiter you do nothing else than NASA. But NASA does many simulation runs on their computers until they have values which are so good, that they can launch the real thing.

The Computer inside the Shuttle is a great tool, but it is not smart at all: It needs the simulation results and ground computations for calculating it's maneuvers.

The Relative Navigation mode (rendezvous with a space station by using star trackers and radar) of the Shuttle is the most autonomous operation, which can run completely without ground data, but generally, the data calculated that way, is compared and improved by ground data.

Still, the shuttle moves much more careful as you would do in Orbiter - they could reach the ISS in a single direct burn theoretically, but this consumes more fuel when something is wrong, than a slow careful approach, which respects possible errors.

During launch, as this was specially asked, there are many different automatic systems active, as well as a large crew on the ground.

You have the launch processing system, which gets used by the ground crew to automatically open valves, activate systems etc. You have the GLS, which does a similar job as the LPS, but runs almost completely without human interaction. You have the onboard computers running as redundant set, for the last 10 seconds of the countdown, starting engines and after lift-off, calculating already closed-loop solutions, even though the guidance is still open-loop during SRB burn time. As soon as the SRBs separate, the control loop get's closed, the solution for main engine cut-off calculated, and when found, the Shuttle follows it's solution. The target for the main engine cut-off is calculated on the ground before the launch, the same applies to all following OMS maneuvers: The nominal targeting data for these burns is calculated before the countdown even started, written on the data tapes which are used inside the Shuttle for loading the computer programs (Called "I-Load").

basically, when you want to fly a perfect mission like the real world shuttle, you have 10 test and simulation flights, and then fly the real mission, with the maneuver data you gained during the earlier simulations.

 

[PaulG]

AH...WOW! Thank you for that enlightening information! I have a MUCH better appreciation for all this. I'm also 30 simulations higher than NASA.


-----Post Added-----


So, is there a launch autopilot that will automatically intercept a particular Inc/LAN and altitude?

 

[Urwumpe]

So, is there a launch autopilot that will automatically intercept a particular Inc/LAN and altitude?

Yes, the so-called "Super-G integration" (similar to the powered explicit guidance), which flys the Shuttle into an orbit. LAN is defined by the launch time, but Inc and argument of periapsis is controlled by it.

 

[tblaxland]

Yes, the so-called "Super-G integration" (similar to the powered explicit guidance), which flys the Shuttle into an orbit. LAN is defined by the launch time, but Inc and argument of periapsis is controlled by it.

Can't the shuttle also make small corrections to LAN whilst in its launch trajectory? I thought so long as it launched within its launch window it was capable of getting to the correct LAN, Inc and ArgP.

 

[Whatu]

I keep hearing this closed-loop and open-loop things. Whats the difference between them?

 

[Urwumpe]

I keep hearing this closed-loop and open-loop things. Whats the difference between them?

Well, control systems are generally viewed as flow charts.

Closed loop guidance means, you have a desired state and compare it to the current state. As you change the current state by the control actuators, the guidance forms a loop: Desired State and Current State effect the control actuators, which effect the current state (for the next iteration).

Open loop guidance does not compare the desired state to the current state. The guidance just calculates the action on the desire state.

A pitch table for example is open loop guidance, the rocket follows a pre-calculated pitch profile during flight (Pitch changes over time).

If the rocket varies pitch to aim for reaching the intended MECO state, you get a closed loop: The effect of the last control action on the final predicted MECO state gets included in the next command.

 

[PaulG]

I'm finding that for autopilots, and planning, I'm the best autopilot with practice as the integrator. Which, seems in line with what NASA does, based on the previous post. I practice, learn, and then get there without a problem.

As I said, I now have a far better appreciation for this....which was a main point of the Orbiter 2006 project!

 

[Whatu]

Well, control systems are generally viewed as flow charts.

Closed loop guidance means, you have a desired state and compare it to the current state. As you change the current state by the control actuators, the guidance forms a loop: Desired State and Current State effect the control actuators, which effect the current state (for the next iteration).

Open loop guidance does not compare the desired state to the current state. The guidance just calculates the action on the desire state.

A pitch table for example is open loop guidance, the rocket follows a pre-calculated pitch profile during flight (Pitch changes over time).

If the rocket varies pitch to aim for reaching the intended MECO state, you get a closed loop: The effect of the last control action on the final predicted MECO state gets included in the next command.

Thanks! I got it now.

 

[PaulG]

One last round of questions.

In real life, does the shuttle perform a roll to bring the tank and belly of the shuttle facing earth? The shuttle launches so it is essentially launching backwards, but I have seen a tutorial that inverts the shuttle in the upper atmosphere (108kkm).

Also, is there some movie or animation on what the shuttle does so I can visually see it? Possibly one with dialogue?

Thanks,
Paul

 

[tblaxland]

In real life, does the shuttle perform a roll to bring the tank and belly of the shuttle facing earth? The shuttle launches so it is essentially launching backwards, but I have seen a tutorial that inverts the shuttle in the upper atmosphere (108kkm).

Yes, it does. IIRC it has done so since the direct ascent trajectory with OMS assist was introduced post-Challenger.

Also, is there some movie or animation on what the shuttle does so I can visually see it? Possibly one with dialogue?

The Shuttle Fleet launch auto-pilot performs this manoeuvre so you could watch that. Also, this video from STS-124 shows the roll at about 6:10. OMS assist starts at about 3:05:

 

[PaulG]

This was great, thank you!
What is the purpose of the roll? I rememebr growing up, at least before as you said Challenger, there was never a roll.

Yes, it does. IIRC it has done so since the direct ascent trajectory with OMS assist was introduced post-Challenger.


The Shuttle Fleet launch auto-pilot performs this manoeuvre so you could watch that. Also, this video from STS-124 shows the roll at about 6:10. OMS assist starts at about 3:05:
YouTube - STS-124 Launch

 

[Urwumpe]

What is the purpose of the roll?

It allows the S-Band antennas on top of the Shuttle to acquire the "Telemetry and Data Relay Satellite" earlier, allowing to use TDRSS for telemetry and communication instead of ground station. If I remember correctly, the antennas which cover the lower hemisphere of the Shuttle are obstructed by the ET.

 

[Brad]

It allows the S-Band antennas on top of the Shuttle to acquire the "Telemetry and Data Relay Satellite" earlier, allowing to use TDRSS for telemetry and communication instead of ground station. If I remember correctly, the antennas which cover the lower hemisphere of the Shuttle are obstructed by the ET.

In addition it is more tolerable for a heads down ascent as the blood tends to drain from the brain in a head up configuration.... and we know what happens when there is no blood in the brain.

 

[Urwumpe]

In addition it is more tolerable for a heads down ascent as the blood tends to drain from the brain in a head up configuration.... and we know what happens when there is no blood in the brain.

Believe me, the astronauts have no idea, where down is. Just like their blood.

They only feel the acceleration of the engines from lift-off on. Their blood is always pressed into their back from T-2 hours to T+8:30 minutes. Which is uncomfortable, but tolerable.

 

[David413]

The roll to heads up was determined to be necessary several years ago when it looked like the Bermuda tracking station was going to be shutdown. That made it necessary to roll to heads up and start communicating with TDRS.

I've flown several ascents in the motion based simulator at JSC, and you are "on-your-back" until MECO since the acceleration of the shuttle is through your back! The only problem with the sim is that you never go above 1G.

 

[Ghostrider]

and we know what happens when there is no blood in the brain.

You become Paris Hilton?