Author Topic: Delta II RP-1 Loading (Read 28825 times)

Jim · « **on:** 11/02/2006 03:19 pm »

How many people know that the reason why the RP-1 on Delta II is loaded late in the countdown?

It is because it is heated to the high 80's F to increase first stage performance

kevin-rf · « **Reply #1 on:** 11/02/2006 03:40 pm »

How?

I would buy to prevent gelling.

or to lower the viscosity allowing for more efficent turbine operation.

An increase of the exhaust temperature by 60 degrees buys you how much of an ISP increase?

Edit : Or the higher temperature allows for more efficent combustion...

Jim · « **Reply #2 on:** 11/02/2006 03:47 pm »

The 3 and 4 solid configurations take a performance hit for early fueling loading (it cools down). They have to load early to add weight to the stack so that the wind does rock it on the launch mount

kevin-rf · « **Reply #3 on:** 11/02/2006 04:04 pm »

Okay Jim, I'm gonna feed the troll a little... I can not find the exhaust temp of the RS-27, so I'm gonna guess 3000 Deg C and your favorite source list the Vac ISP at 303.

So if 3000 (Yes I sould convert from C to Kelvin, but I don't have a real exhaust temp) = 303 ISP

Boosting the Fuel Temp by ~30 Deg Kelvin would result in (3000 + 30) * 303 ISP / (3000) = 306 ISP

So you gain a 3 in your vehicle ISP?

How close am I?

kevin-rf · « **Reply #4 on:** 11/02/2006 04:11 pm »

So does that translate into a roughly 1% increase in the first stage Delta V?

Jim · « **Reply #5 on:** 11/02/2006 05:11 pm »

I don't know the exact numbers, the but early loading hit was on the order of XX fps.

Edit:
Still looking for the hit

Propforce · « **Reply #6 on:** 11/02/2006 05:44 pm »

Quote

Jim - 2/11/2006 8:02 AM

How many people know that the reason why the RP-1 on Delta II is loaded late in the countdown?

It is because it is heated to the high 80's F to increase first stage performance

Quote

kevin-rf -2/11/2006 8:47 AM

Okay Jim, I'm gonna feed the troll a little... I can not find the exhaust temp of the RS-27, so I'm gonna guess 3000 Deg C and your favorite source list the Vac ISP at 303.

So if 3000 (Yes I sould convert from C to Kelvin, but I don't have a real exhaust temp) = 303 ISP

Boosting the Fuel Temp by ~30 Deg Kelvin would result in (3000 + 30) * 303 ISP / (3000) = 306 ISP

So you gain a 3 in your vehicle ISP?

How close am I?

LOL... that's not the reason at all. RP-1 is used to regeneratively cool the RS-27A combustion chamber therefore the fuel is heated up already prior to combustion.

The reason is completely opposite, that is to load the RP-1 late to keep the fuel cool

The cooler the RP-1 fuel is, the higher density it is, therefore one can load more fuel into the existing volume tank, hence boosting the first stage performance.

Jim · « **Reply #7 on:** 11/02/2006 05:52 pm »

No, the fuel is actively heated before it is loaded. The ground RP-1 system has heaters. The RP-1 is unloaded after every attempt so that it can be heated again.

Edit:

I can count another "no", since you didn't know this

Propforce · « **Reply #8 on:** 11/02/2006 06:30 pm »

Just talked to my Delta II propellant guru ....

You were right, the RP is heated to increase the overall vehicle performance. Even though this reduces propellant density thereby reducing the total RP-1 loading, it still provides an overall vehicle delta-vee advantage.

This practice is opposite of what Atlas II and Sealaunch were doing, from what I understand. Both were chilling their propellants to maximize mass loading.

Now why the difference approach, that's a good question...

edkyle99 · « **Reply #9 on:** 11/02/2006 06:46 pm »

Quote

Propforce - 2/11/2006 1:13 PM

Just talked to my Delta II propellant guru ....

You were right, the RP is heated to increase the overall vehicle performance. Even though this reduces propellant density thereby reducing the total RP-1 loading, it still provides an overall vehicle delta-vee advantage.

This practice is opposite of what Atlas II and Sealaunch were doing, from what I understand. Both were chilling their propellants to maximize mass loading.

Now why the difference approach, that's a good question...

My guess would be that the differing approaches have to do with the fact that the Atlas and Zenit engines, which provide all or most of the liftoff thrust, are optimized for thrust while the Delta II engine, which provides less than 20% of the liftoff thrust on the "79XX" models, leans more toward vacuum optimization. Or, from another perspective, it is because the Atlas and Zenit engines burn a much higher fraction of total vehicle mass in fuel than the Delta II engine does, so fuel density is relatively more important for Atlas and Zenit while that extra bit of specific impulse is relatively more important for Delta II.

- Ed Kyle

Jim · « **Reply #10 on:** 11/02/2006 07:02 pm »

Atlas V loads the RP-1 once for WDR and leaves it in until launch. So it is subjected to the ambient temps and therefore not chilled.
Zenit is different and is detanked after every attempt.

Jim · « **Reply #11 on:** 11/02/2006 07:03 pm »

The heating of the Delta fuel increases the total energy of the system

Propforce · « **Reply #12 on:** 11/02/2006 08:19 pm »

IT was Atlas II and not Atlas V

Jim · « **Reply #13 on:** 11/02/2006 09:40 pm »

Quote

Propforce - 2/11/2006 4:02 PM

IT was Atlas II and not Atlas V

They didn't detank after WDR neither

LaunchOps · « **Reply #14 on:** 03/16/2007 10:09 am »

The fuel transfer tube goes through the middle of the LOX tank, the fuel is loaded "late" and heated to keep it from starting to freeze. LOX load time also constains the launch window, as after about 160 mins the RP-1 in the transfer tube begins to gel.

bigdog · « **Reply #15 on:** 03/16/2007 10:00 pm »

Quote

Jim - 2/11/2006 1:02 PM

Atlas V loads the RP-1 once for WDR and leaves it in until launch. So it is subjected to the ambient temps and therefore not chilled.
Zenit is different and is detanked after every attempt.

Is that just if the WDR is close to launch? I'm told by someone who supported the STP launch that it was loaded the day before after they rolled out. Also wouldn't that make things more hazardous having it loaded during the transport and during the down time at the VIF?

Jim · « **Reply #16 on:** 03/17/2007 12:39 pm »

Quote

bigdog - 16/3/2007 7:00 AM

Quote
Jim - 2/11/2006 1:02 PM

Atlas V loads the RP-1 once for WDR and leaves it in until launch. So it is subjected to the ambient temps and therefore not chilled.
Zenit is different and is detanked after every attempt.

Is that just if the WDR is close to launch? I'm told by someone who supported the STP launch that it was loaded the day before after they rolled out. Also wouldn't that make things more hazardous having it loaded during the transport and during the down time at the VIF?

Not really, it is only RP-1. There are plans that when/if they eliminate WDR's, they would load RP-1 in the VIF.

publiusr · « **Reply #17 on:** 03/30/2007 07:31 pm »

Jim, if you were given supervision over Zenit's fuel loading, would you heats its RP, and or change any of the fuel handling?

Jim · « **Reply #18 on:** 03/31/2007 12:17 am »

Quote

publiusr - 30/3/2007 3:31 PM

Jim, if you were given supervision over Zenit's fuel loading, would you heats its RP, and or change any of the fuel handling?

Don't know what the RD-170 needs. it is automated so it doesn't matter.

Liryc · « **Reply #19 on:** 10/16/2012 03:27 pm »

Hi guys,

I was wondering hor the RP1 and LOX are fueled in the launcher ?
I only see what seems to be air conditionned and electrical connections betweek the tower and the launcher..

Cheers !
cyril