Project Soyuz 7k.dll

[N_Molson]

Uh in fact I realized I made a calculation error in my Dv counter. It was working with 1 tank only.

I fixed it and with the 380 kg setting, the Dv is only 156.39 m/s :blink:... Does that seem OK to you ?

Now the total mass including the crew is 6912 kg, which seems fairly accurate.

Edit : funny, burning RCS fuel raises the Dv potential of the ship. Logical, but I wasn't thinking to it...

 

[Urwumpe]

seems a bit low to me, but then, you calculated likely the wrong way to be accurate... Astronautix likely calculated with 500 kg fuel for the main engines, you possibly calculated with only the main engine fuel being consumed.

I think the real value is somewhere around 180 m/s, this would permit the historic missions and still mean that Soyuz is immobile (like it was until Soyuz T)

 

[N_Molson]

you possibly calculated with only the main engine fuel being consumed.

Yes, that what I meant. Only for the main engine fuel.

 

[Urwumpe]

Yes, that what I meant. Only for the main engine fuel.

Yes, but during a normal mission, DPO and DO fuel is consumed as well, lowering the mass that does not contribute directly to propulsion.

 

[N_Molson]

Well, if I calculate the Dv for the main engine and the DPO thrusters, I get 171.43 m/s. If we add the DO we probably get your 180 m/s, but it shouldn't count in the display that indicates how much Dv remains, since the DO thrusters can only rotate the spacecraft, not translate it, so a crew with only a full DO tank would anyway be stranded, even if 10 m/s lacked to get a quick orbit decay (well anyway with the 48-hours battery of the 7K-T, that's not even an option).

 

[Urwumpe]

Wait a minute, calculating it with OpenOffice...

 

[N_Molson]

(How I do it ) :

	double PropMass = GetPropellantMass(ph_N2O4);
	double M0divM1 = GetMass()/(GetMass()-PropMass);	
	double logM0divM1 = log(M0divM1);
	double DeltaV_1 = GetThrusterIsp(th_main[0])*logM0divM1;

	double PropMass_2 = GetPropellantMass(ph_H2O2_DPO);
	double M0divM1_2 = GetMass()/(GetMass()-PropMass_2);				
	double logM0divM1_2 = log(M0divM1_2);								
	double DeltaV_2 = GetThrusterIsp(th_rcs[28])*logM0divM1_2;	

	double DeltaV = DeltaV_1 + DeltaV_2;

 

[Urwumpe]

Total mass|6912|kg
SDKU propellant|370|kg
DPO/DO propellant|130|kg
Empty mass |6412|kg
KT-35 Thrust|4090|N
KT-35 Specific Impulse|2746.8|m/s
Stage burn time|248.49|s
SDKU mass flow|1.49|kg/s
DPO/DO mass flow|0.52|kg/s
corrected ISP|2032.63|m/s
Stage DV|152.63|m/s

 

[N_Molson]

That's near the 156 m/s I found on the other post... So what are we missing, or what is wrong in the code-calculation I posted above ?

 

[Urwumpe]

That's near the 156 m/s I found on the other post... So what are we missing, or what is wrong in the code-calculation I posted above ?

Not sure if we are missing something. I just plugged the numbers into it and assumed, that the DPO contributes almost nothing to velocity change. That is of course wrong, but the best approximation possible.

Looks like Soyuz has really only enough fuel for docking and de-orbit.

 

[N_Molson]

Right, so 153-156 m/s for the KT-35, and 15-20 more m/s for the DPO if used completely in linear mode. :yes:

BTW I noticed you use 370 as a value, but 500 - (90+30) ) = 380. Do the missing 10kg account for a N2 pressurization tank ?

 

[Urwumpe]

BTW I noticed you use 370 as a value, but 500 - (90+30) ) = 380. Do the missing 10kg account for a N2 pressurization tank ?

I thought you used 130 kg for it in total. :lol: I have no good idea yet on the DO tank volume.

If at all, Nitrogen will contribute to empty mass, since it is not vented overboard.

With 120 kg for peroxide i get 156.75 m/s dV

 

[N_Molson]

Oh ok, I did as you suggested, DO tank = 1/3 DPO tank. So 90 kg for DPO and 30 kg for DO.

The 120 kg of Peroxyde only give 4 m/s of Dv ? Even with the low ISP, I slightly doubt of that, "my" 15 m/s seem more plausible :hmm:

 

[Urwumpe]

The 120 kg of Peroxyde only give 4 m/s of Dv ? Even with the low ISP, I slightly doubt of that, "my" 15 m/s seem more plausible :hmm:

See above, I excluded the DPO from the total DV, since it is not exclusively used for translations. It can contribute to the total dV, but don't ask me, how much of the DPO is going there.

 

[N_Molson]

Right right, I think we are precise enough for now. But a mission to a Salyut is going to be super-challenging (not for those that find that docking Thorton's ISS with the TMA is hard) :lol:



I admit it, that pic was taken using the scenario editor :blush:

Edit : the docking port was uncorrectly rotated. Fixed.

 

[Urwumpe]

Yes, but if you use the DPO completely and only for translations, you will get 172.66 m/s DV all together in my spreadsheet - not that little, but also pretty abstracted.

---------- Post added at 06:58 PM ---------- Previous post was at 05:40 PM ----------

The placement of the SA thrusters and the CoG of the SA needs some more work, they are badly off - firing the roll thrusters should not cause anything else but roll. They did back then even put small weights into the capsules to fine tune the weight for each astronaut and payload loaded.

 

[N_Molson]

The placement of the SA thrusters and the CoG of the SA needs some more work, they are badly off - firing the roll thrusters should not cause anything else but roll. They did back then even put small weights into the capsules to fine tune the weight for each astronaut and payload loaded.

(Issue#018)

Well, the thrusters are exactly located where you can see the exhausts. It's why I kept them so visible. Concerning the roll thrusters, maybe it's also a matter of direction ; this is a 3D vector and I remember I had difficulties with it (the exhausts don't match perfectly the nozzles).

-> I will see what I can do. -> Shifted the direction of the yaw thrusters a little inwards and backwards, but there is still undesired torque on X & Z.

 

[Urwumpe]

(Issue#018)

Well, the thrusters are exactly located where you can see the exhausts. It's why I kept them so visible. Concerning the roll thrusters, maybe it's also a matter of direction ; this is a 3D vector and I remember I had difficulties with it (the exhausts don't match perfectly the nozzles).

-> I will see what I can do.

It isn't that hard, since the thrusters are all pointed orthogonal to the respective radius vector. if you know the position and the plane of the thruster, you can calculate the direction. In the other direction, by having coarse guesses about the direction of the thrusters, you can limit the position of the CoG in the SA.

 

[N_Molson]

It isn't that hard, since the thrusters are all pointed orthogonal to the respective radius vector.

That was the problem. The roll thrusters (those that are at the base of the SA), have a "nozzle exit" that points slightly upwards (10°-15°), it's where I had trouble.

But maybe this is just a way to protect the thruster from re-entry that doesn't affect the direction of the thrust (though, if the exhaust jet hits something, the thrust is slightly deviated, no ?) ?

 

[Urwumpe]

But maybe this is just a way to protect the thruster from re-entry that doesn't affect the direction of the thrust (though, if the exhaust jet hits something, the thrust is slightly deviated, no ?) ?

No, it is actually just a small imbalance of the SA mass, the one that gives it its automatic angle of attack during reentry.

If you look at a drawing or a good photo, you can see how the thrusters aim (orthogonal) at the CoG