Project CST-100

[francisdrake]

Now that's a good one! The launchpad LC-41 towers up vertical
Makes launching somewhat challenging!
Did I miss something, an update or so?

____
Edit: Ok, tried it on a clean install, no problem there.
Guess I have to clean out my Orbiter installation from time to time.

 

[Kyle]

Which BETA version are you using? That might be the problem.

 

[N_Molson]

BTW the addon is Orbiter 2010 P1 compatible, I can't promise anything with the Beta versions. The latest changed a lot of things about touchdown points, so I'd guess that your bug was related to that.

 

[ky]

Might want to take a look at this http://www.flightglobal.com/news/articles/boeing-progressing-on-cst-100-space-capsule-384520/

 

[Urwumpe]

Might want to take a look at this http://www.flightglobal.com/news/articles/boeing-progressing-on-cst-100-space-capsule-384520/

So the abort thrusters are also used for orbital maneuvers, but at a lower thrust?

 

[N_Molson]

So the abort thrusters are also used for orbital maneuvers, but at a lower thrust?

It's a bit hard to believe, because they are 258 kN each. Usually, rocket engines can't be throttled below 50% (at best). And all those thrusters in the pods seem to be enough for orbital manoeuvers. I would not be surprised if there was again some confusion in the article.

 

[garyw]

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain boeing.com by stl-mbsin-02.boeing.com. [130.76.96.48]."

I guess they thought I was the Chinese

No, they've blocked all mail from freemail addresses as thats where spammers like to send from. I have considered doing the same thing myself.

 

[Urwumpe]

It's a bit hard to believe, because they are 258 kN each. Usually, rocket engines can't be throttled below 50% (at best). And all those thrusters in the pods seem to be enough for orbital manoeuvers. I would not be surprised if there was again some confusion in the article.

Well, if I understand the previous articles correctly, it was planned to feed the engines at 1000 psi during the abort. If you would operate the tanks at the lower standard pressure, thrust and specific impulse of the abort engines would be lower, but they should still function.

---------- Post added at 10:33 AM ---------- Previous post was at 10:32 AM ----------

No, they've blocked all mail from freemail addresses as thats where spammers like to send from. I have considered doing the same thing myself.

I have a non-free mail address...

 

[N_Molson]

Another small piece of the puzzle, or maybe just more questions :

http://www.aerospace-technology.com/news/newsboeings-cst-100-spacecraft-completes-thruster-tests

“The 1,500lb force thrust class engine achieved full thrust while validating key operating conditions. (Terry Lorier, Pratt & Whitney Rocketdyne’s Commercial Crew Development program manager)”

So if I understood well each of the "big thrusters" in the pods is rated to 1500 lbf, or 6.67 kN, which would mean 133.4 kN if we sum up the 20. That seems a lot for me (especially for a LEO vehicle), more than Apollo in fact. What do you think guys ?

The spacecraft's service module can accommodate 24 OMAC thrusters.

More probably 28, else I don't see how the spacecraft is going to translate during docking approach. :idk:

Here's one of those "OMAC" thrusters during a test (source : NASA)

 

[Urwumpe]

So if I understood well each of the "big thrusters" in the pods is rated to 1500 lbf, or 6.67 kN, which would mean 133.4 kN if we sum up the 20. That seems a lot for me (especially for a LEO vehicle), more than Apollo in fact. What do you think guys ?

I think it works out. It is less than twice the thrust of the Space Shuttle PRCS (which had 870 lbf thrust per thruster). A single Space Shuttle OMS engine produces 6000 lbf thrust.

20 x 1500 = 5 * 6000 lbf

Since the engines are supposed to assist during an abort, it is thinkable, that the thrust of those engines is much higher than necessary for orbital maneuvers - maybe they simply use not all thrusters during orbital maneuvers, but let the computer alternate the thrusters used for extending life time.

EDIT: If I remember correctly, 30,000 lbf thrust by the OMACs would result in about 1 g acceleration.

 

[N_Molson]

maybe they simply use not all thrusters during orbital maneuvers, but let the computer alternate the thrusters used for extending life time.

Yes, that's definitively an option.

Good, we're going forward. :yes:

 

[Urwumpe]

For implementing the alternating thruster uses (for example in pairs), you simply need a bool variable in the vehicle DLL for storing a flag (Name it as you like, I would call it "RCSACTTH" on a bad day and "bTranslationalRCSActive" when I am verbose).

In PostStep:

When the thruster group level is bigger than 0 (or a small value like 0.05), you set the flag. When the thruster group level is less than the threshold (or zero) and the flag is set, you redefine the thruster group to use a different thruster pair, kill all remaining thrust on the previous thruster pair and reset the flag again.

This time, every time the player uses linear forward RCS, it keeps on using the engines while he presses the key, but switches to new engines for the next burn.

If this is too simple, you can also make the thruster pairs alternate by time intervals... but this requires a new variable...

 

[N_Molson]

I like the idea... Also there could be different modes available, like x2, x4, x10, x20 ...

---------- Post added at 01:36 PM ---------- Previous post was at 01:18 PM ----------

Another small problem : when the LES is activated (now it also activate the 20 "main" thrusters), the dynamic pressure peaks to 87 kPa. Would the capsule structure endure that, provided it lasts no more than a few seconds ? The only way to counter that would be a throttle down, or maybe it is not necessary to burn all the fuel ? :hmm: According to Apollo figures, I guess that staying below 40-45 kPa is a good idea. Escaping a rocket explosion to be crushed by the shell of the capsule is well... not that interesting :lol:

 

[Urwumpe]

I like the idea... Also there could be different modes available, like x2, x4, x10, x20 ...

---------- Post added at 01:36 PM ---------- Previous post was at 01:18 PM ----------

Another small problem : when the LES is activated (now it also activate the 20 "main" thrusters), the dynamic pressure peaks to 87 kPa. Would the capsule structure endure that, provided it lasts no more than a few seconds ? The only way to counter that would be a throttle down, or maybe it is not necessary to burn all the fuel ? :hmm: According to Apollo figures, I guess that staying below 40-45 kPa is a good idea. Escaping a rocket explosion to be crushed by the shell of the capsule is well... not that interesting :lol:

If you stay by Apollo, you should start an abort exactly that way even at 900 lb/ft² (43 kPa) dynamic pressure. That limit was tested during the Little-Joe tests. The additional dynamic pressure was below the design limits for the CM.

And luckily for the CST-100, you don't have to include the additional pressure of the LES exhaust pushing against the CM.

 

[N_Molson]

You mean that the LES can be triggered even when the DynP is already at 43 kPa, or that it should be cut short to be sure that this thresold isn't exceeded ?

 

[Urwumpe]

You mean that the LES can be triggered even when the DynP is already at 43 kPa, or that it should be cut short to be sure that this thresold isn't exceeded ?

Even if you are already at 43 kPa, you can still trigger the abort. That was the "overperforming Saturn V" scenario, with the engines being at the optimal possible performance.

Of course, an abort at MaxQ is a good way to make a rough ride a lot rougher... spacecraft rodeo. That is the point where I would love to let the panels and objects in the VC shake visibly...

 

[N_Molson]

OK, so high dynamic pressure is not really an issue for the capsule, heat would probably destroy it before, am I correct ? (and I've seen one of those schematics where some grey tiles just below the CST-100 nose cone are labeled as "forward heat shield").

With the 432 configuration (3 SRM), I get 42.74 kPa at MaxQ (funny how close it is from the Saturn V 43 kPa !), and if I trigger the abort at this moment, it rises to 80 kPa (the atmosphere density decreases quickly at this point). So, I'd say it is within the safety limits :yes:

 

[Urwumpe]

With the 432 configuration (3 SRM), I get 42.74 kPa at MaxQ (funny how close it is from the Saturn V 43 kPa !), and if I trigger the abort at this moment, it rises to 80 kPa (the atmosphere density decreases quickly at this point). So, I'd say it is within the safety limits :yes:

You should also test a few seconds before MaxQ for verification, should result in a few kPA more dynamic pressure.

In more detailled flight, the SM thrusters will very likely pitch the capsule downward rapidly for maximizing the distance between capsule and launch vehicle = a tiny bit more dynamic pressure.

---------- Post added at 05:17 PM ---------- Previous post was at 05:15 PM ----------

For some more reading about the abort tests of Apollo:

http://klabs.org/history/apollo_experience_reports/tn-d7083_apollo_launch_escape_propulsion.pdf

 

[ky]

Of course, an abort at MaxQ is a good way to make a rough ride a lot rougher... spacecraft rodeo. That is the point where I would love to let the panels and objects in the VC shake visibly...

Looks like I'll have to work on the VC some more..

 

[Urwumpe]

Looks like I'll have to work on the VC some more..

Don't forget the plushfuzzy dices. :lol: