We are getting near the point where the Briz-M has failed in the past, sometimes due to the main engine plumbing failing
We are getting near the point where the Briz-M has failed in the past, sometimes due to the main engine plumbing failing.There *are* 4 FGB-class auxiliary thrusters pointed in the right direction, but these are plumbed to the main prop tank, apparently, these are connected to a smaller "high pressure" prop tank. Since these are fired to provide acceleration for the start of the main engine firing, I suspect that they are required to have higher than normal pressure in the prop tanks (with "normal" being the tank pressure when the thrusters are used at ISS).I would imagine that if Briz fires multiple times, these auxiliary propulsion prop tanks are pretty much empty by the end of the mission; otherwise, they could be used to provide a little extra delta-V as verniers.
2nd Briz-M burn completed: lasted 1039s for 1066s nominal
Quote from: input~2 on 10/25/2013 07:44 pm2nd Briz-M burn completed: lasted 1039s for 1066s nominalWhy does it often seem to burn under the nominal length, I have noticed this before?
Quote from: Danderman on 10/25/2013 08:34 pmWe are getting near the point where the Briz-M has failed in the past, sometimes due to the main engine plumbing failing.There *are* 4 FGB-class auxiliary thrusters pointed in the right direction, but these are plumbed to the main prop tank, apparently, these are connected to a smaller "high pressure" prop tank. Since these are fired to provide acceleration for the start of the main engine firing, I suspect that they are required to have higher than normal pressure in the prop tanks (with "normal" being the tank pressure when the thrusters are used at ISS).I would imagine that if Briz fires multiple times, these auxiliary propulsion prop tanks are pretty much empty by the end of the mission; otherwise, they could be used to provide a little extra delta-V as verniers.There is no "auxiliary propulsion prop tank". The 11D458 engines take their propellant in the same tanks as S5.98M main engine.
The Briz-M (Breeze-M) upper stage is the Phase III variant, a recent upgrade which utilizes two new high-pressure tanks (80 liters) to replace six smaller tanks
Exact launch time is 18:08:53.957 UTC.Quote from: Danderman on 10/25/2013 08:34 pmWe are getting near the point where the Briz-M has failed in the past, sometimes due to the main engine plumbing failingExactly! How do you think what will be this time? Your thoughts are very important!
Quote from: Nicolas PILLET on 10/25/2013 09:47 pmQuote from: Danderman on 10/25/2013 08:34 pmWe are getting near the point where the Briz-M has failed in the past, sometimes due to the main engine plumbing failing.There *are* 4 FGB-class auxiliary thrusters pointed in the right direction, but these are plumbed to the main prop tank, apparently, these are connected to a smaller "high pressure" prop tank. Since these are fired to provide acceleration for the start of the main engine firing, I suspect that they are required to have higher than normal pressure in the prop tanks (with "normal" being the tank pressure when the thrusters are used at ISS).I would imagine that if Briz fires multiple times, these auxiliary propulsion prop tanks are pretty much empty by the end of the mission; otherwise, they could be used to provide a little extra delta-V as verniers.There is no "auxiliary propulsion prop tank". The 11D458 engines take their propellant in the same tanks as S5.98M main engine.I have a dim memory of there being high pressure prop tanks for the auxiliary thrusters. Actually, it's more than a dim memory:http://www.nasaspaceflight.com/2013/03/ils-proton-m-launch-satmex-8/QuoteThe Briz-M (Breeze-M) upper stage is the Phase III variant, a recent upgrade which utilizes two new high-pressure tanks (80 liters) to replace six smaller tanksIf the auxiliary thrusters and the main engine both share the same prop tank(s), why does failure of the main engine result in end of mission? Why can't the four 40 kg thrusters simply fulfill at least part of the remaining mission?
The Breeze M is then delivered to Building 44 in Area 31, the propellant fueling hall, where MMH and N2O4 are loaded in the high pressure tanks of the low-thrust settling/attitude control system thrusters.Proton Launch System Mission Planner’s Guide, LKEB-9812-1990 Revision 7, July 2009
As always, let's all try and get a really nice launch image for the article (which will go on at launch).