Was the space shuttle really like the one in Orbiter?

[DelRioPilot]

I ask this in a general sense. Of course the one in Orbiter does not model the full suite of switches, and does not model the flight dynamics, damage characteristics, etc perfectly.

But in real life, was it possible to sort of hand fly the shuttle freely, while throttling the OMS at will? I notice in the cockpit there is what looks to be a throttle. Did that control the OMS?

 

[romanasul]

I ask this in a general sense. Of course the one in Orbiter does not model the full suite of switches, and does not model the flight dynamics, damage characteristics, etc perfectly.

But in real life, was it possible to sort of hand fly the shuttle freely, while throttling the OMS at will? I notice in the cockpit there is what looks to be a throttle. Did that control the OMS?

No, the shuttle could not be throttled. The on board computer controlled everything. To perform a maneuver the delta v was entered I believe in feet per second and the time to the maneuver. Of course all this data was given by mission control. There is a much more realistic alternative to the stock Orbiter shuttle and Shuttle Fleet called SSU (Space Shuttle Ultra). It's not completed yet but it offers excellent functionality.

 

[DelRioPilot]

No, the shuttle could not be throttled. The on board computer controlled everything. To perform a maneuver the delta v was entered I believe in feet per second and the time to the maneuver. Of course all this data was given by mission control. There is a much more realistic alternative to the stock Orbiter shuttle and Shuttle Fleet called SSU (Space Shuttle Ultra). It's not completed yet but it offers excellent functionality.

So the "throttle" looking thing seen at both the Commander and Pilot positions... what was that exactly?

Thanks for the recommendation on SSU. I did try it out a bit, but will probably use it more when it's complete. I currently use Shuttle Fleet in conjunction with AutoFCS which does retro burns automatically.

With that said though, is there an MFD addon which allows you to do burns automatically with a set DV and time?

 

[DaveS]

The throttle was for the SSMEs during ascent and the speed brake during descent. It served no purpose during on-orbit ops and was just a emergency thing when the GPCs wasn't working correctly. Normally all throttle activities was done automatically by the GPCs but the crew could switch to a semi-manual mode where they used the throttle to command a level and the GPCs carried it out.

 

[Cras]

With that said though, is there an MFD addon which allows you to do burns automatically with a set DV and time?

Yes

I use Shuttle Fleet (if I want to fly the Shuttle and flip more switches I will fly a mission in SSMS) but to simulate the way various OMS burns were done, I use DVTools to get me a solution, and I then use IMFDs Delta V Program to actually do the burn.

Requires a few changes to the default settings in IMFD, such as turn off the auto throttle down and RCS features (set them to zero) as the Shuttle didnt throttle the OMS, it was either on or off. Instead of throttling you could set up for either both engines to burn, only one of them, or do an RCS only burn.

With using SF and IMFD you only have the option to burn both OMS or RCS, but it does add realism. I dont really like using a throttle when flying in Orbiter so I use this for most burns I do. I get no satisfaction in doing things by hand and find setting up burns for x amount of seconds at a specific time much more rewarding in terms of getting the ship to where I want it to go.

 

[BruceJohnJennerLawso]

The throttle was for the SSMEs during ascent and the speed brake during descent. It served no purpose during on-orbit ops and was just a emergency thing when the GPCs wasn't working correctly. Normally all throttle activities was done automatically by the GPCs but the crew could switch to a semi-manual mode where they used the throttle to command a level and the GPCs carried it out.

Why a manual backup for the SSMEs but not the OMS? More critical situation during ascent? (less time/ways to fix the problem maybe)

 

[DelRioPilot]

The throttle was for the SSMEs during ascent and the speed brake during descent.

So, when told "go at throttle up," the throttle could in theory be advanced? But it was usually done automatically, requiring no input from the pilots?

I use Shuttle Fleet (if I want to fly the Shuttle and flip more switches I will fly a mission in SSMS)

I'm with you on this. When it comes to Orbiter, I only care about getting most of the general concepts realistic, not the intricate little things. Thanks for the addon info by the way. I'll be looking into those.

I do still find it strange that the STS didn't have the option for a throttleable OMS. It's my understanding that the Dream Chaser will have this functionality.

 

[Cosmic Penguin]

So, when told "go at throttle up," the throttle could in theory be advanced? But it was usually done automatically, requiring no input from the pilots?



I'm with you on this. When it comes to Orbiter, I only care about getting most of the general concepts realistic, not the intricate little things. Thanks for the addon info by the way. I'll be looking into those.

I do still find it strange that the STS didn't have the option for a throttleable OMS. It's my understanding that the Dream Chaser will have this functionality.

Ah, the misnomer of "go at throttle up"......

It actually is just a call out that all systems are functioning normally at the point where the SSME throttle back up to 104% thrust - all nominal SSME actions are controlled by each engine's own computer.

 

[Linguofreak]

So, when told "go at throttle up," the throttle could in theory be advanced? But it was usually done automatically, requiring no input from the pilots?

Note that the wording is "go at throttle up" not "go for throttle up". "Throttle up" in this context was just a name for a certain point in the flight timeline (namely, that at which the computer throttled up the engines if everything was going well), and "go at throttle up" just meant that nothing had gone wrong by that point, so the launch could continue as usual.

If manual control of the throttles were ever required at the throttle up point, the "go at throttle up" call would never have been given, and some sort of abort would have begun as soon as booster separation occurred.

 

[Urwumpe]

Why a manual backup for the SSMEs but not the OMS? More critical situation during ascent? (less time/ways to fix the problem maybe)

The OMS simply can't be throttled. The valves only know open and closed. Also if you had not even Backup Flight System (The fifth GPC running on a different software) available, you had been unable to reenter. You can't fly the orbiter without Fly-by-Wire. And for the OMS engines you had the RCS as backup anyway.

 

[BruceJohnJennerLawso]

The OMS simply can't be throttled. The valves only know open and closed. Also if you had not even Backup Flight System (The fifth GPC running on a different software) available, you had been unable to reenter. You can't fly the orbiter without Fly-by-Wire. And for the OMS engines you had the RCS as backup anyway.

So an OMS failure would have implied a general fly-by-wire failure, which would have mandated a rescue mission anyways... makes sense.

 

[Izack]

So an OMS failure would have implied a general fly-by-wire failure, which would have mandated a rescue mission anyways... makes sense.

If an OMS engine failed, but the GPCs were still operating, manoeuvres could still be done under FBW with the remaining OMS, or with the RCS. So an OMS failure doesn't imply FBW failure, but the opposite is essentially true. AFAIK.

As I understand it, it is also possible to redirect OMS propellant into the RCS, though, as mentioned earlier, efficiency there is significantly lower.

 

[Urwumpe]

As I understand it, it is also possible to redirect OMS propellant into the RCS, though, as mentioned earlier, efficiency there is significantly lower.

Yes, OMS to RCS is possible, but not the other way around, because the OMS tank pressure is higher.

 

[BruceJohnJennerLawso]

Yes, OMS to RCS is possible, but not the other way around, because the OMS tank pressure is higher.

Was a similar mechanism available to route Apollo SPS propellants to the SCS? Rather clever, I should say though.

 

[Urwumpe]

Was a similar mechanism available to route Apollo SPS propellants to the SCS? Rather clever, I should say though.

No, since it had four separate SM RCS systems, one for each Quad.