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#120 by William Graham on 05 Nov, 2007 01:11
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tnphysics - 5/11/2007 2:04 AM
I assume that it is almost in orbit prior to engine start.
I think it probably is. Without an upper stage, Proton can still make LEO, and has been seen to do so with some pretty heavy loads (Salyut, Zarya, Zvezda, etc). -
#121 by edkyle99 on 05 Nov, 2007 01:12
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tnphysics - 4/11/2007 8:04 PM
Why does the Breeze-M have such a low thrust/weight ratio?
I assume that it is almost in orbit prior to engine start.
It only performs a final short burn to reach a parking orbit, then performs all of the on-orbit transfer burns. Since the transfer burns add velocity horizontal to the gravity vector, essentially no gravity losses result and there is no need to worry too much about thrust-to-weight ratios. The only negative thing about the low thrust is that the transfer orbit burns have to be broken into a series of burns, extending the length of the mission. The payback is terrific, however, since Briz-M has one of the most efficient, if not the most efficient, hypergolic propulsion systems ever flown.
Also keep in mind that Briz-M uses drop tanks. The tankage is dropped after it is emptied, decreasing the dry mass and increasing the thrust-to-weight ratio for the latter burns.
Why the low thrust? I've heard it expressed this way. Thrust costs money. If you can perform a mission with less thrust, it should cost less.
- Ed Kyle -
#122 by Nicolas PILLET on 30 Nov, 2007 17:12
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I have a little question about Cosmos-3M.
In the scheme displayed on this web page : http://www.roscosmos.ru/Roket1Show.asp?RoketID=21
What means the sentence "pribornyi otsek" ?
Thank you very much for help ! -
#123 by DarthVader on 30 Nov, 2007 17:24
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If I'm not mistaken "pribornyi otsek" means "Service Module" (e.g Soyuz' service module located "after" the Re-entry module). Might be different meaning for thet particular schema ...
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#124 by anik on 30 Nov, 2007 18:01
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Nicolas PILLET - 30/11/2007 9:12 PM
What means the sentence "pribornyi otsek"?
Priborniy otsek means compartment, which contains equipment (instruments) of control system and unites the second stage with fairing...
But priborniy otsek is not that denoted by two arrows on scheme... -
#125 by Danderman on 30 Nov, 2007 18:11
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Nicolas PILLET - 30/11/2007 10:12 AM I have a little question about Cosmos-3M. In the scheme displayed on this web page : http://www.roscosmos.ru/Roket1Show.asp?RoketID=21 What means the sentence "pribornyi otsek" ? Thank you very much for help ![/QUOTE]
It could mean "compartment for devices" or "instrument compartment".
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#126 by anik on 30 Nov, 2007 18:25
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By the way, the explanation of this scheme in English is more correct than in Russian...
http://www.roscosmos.ru/Roket1Show.asp?Lang=ENG
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#127 by Nicolas PILLET on 30 Nov, 2007 18:26
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anik - 30/11/2007 8:01 PM
But priborniy otsek is not that denoted by two arrows on scheme...
OK, it was that point which looked strange to me !
But in this case, what are the two objects pointed by the two arrows ? -
#128 by anik on 30 Nov, 2007 18:44
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Nicolas PILLET - 30/11/2007 10:26 PM
But in this case, what are the two objects pointed by the two arrows?
See the image above...
It is low-thrust system, which contains tanks and engines for stabilization of rocket during flight between the first and second burns of engine 11D49 of the second stage... -
#129 by meiza on 30 Nov, 2007 19:42
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Gas deflectors!? Does this rocket use jet vanes, in 2007?
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#130 by Skyrocket on 30 Nov, 2007 21:52
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meiza - 30/11/2007 9:42 PM
Gas deflectors!? Does this rocket use jet vanes, in 2007?
Yes!
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#131 by Danderman on 15 Dec, 2007 14:25
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This is definitely the wrong place to ask, but what is the difference between the Zenit 2SLB and Zenit 3SLB now described in the launch calendar? Isn't Zenit2-SLB an inappropriate designator, and shouldn't it be "Zenit 2M"?
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#132 by Jim on 15 Dec, 2007 14:37
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Danderman - 15/12/2007 10:25 AM
This is definitely the wrong place to ask, but what is the difference between the Zenit 2SLB and Zenit 3SLB now described in the launch calendar? Isn't Zenit2-SLB an inappropriate designator, and shouldn't it be "Zenit 2M"?
No, the 2SLB uses the 3SLB fairings and adapters, which Boeing provides -
#133 by anik on 15 Dec, 2007 14:51
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Danderman - 15/12/2007 6:25 PM
what is the difference between the Zenit 2SLB and Zenit 3SLB now described in the launch calendar?
On Novosti kosmonavtiki forum I was told Zenit-2SLB is Zenit with Fregat-SB upper stage and Zenit-3SLB is Zenit with DM-SLB upper stage...QuoteDanderman - 15/12/2007 6:25 PM
Isn't Zenit2-SLB an inappropriate designator, and shouldn't it be "Zenit 2M"?
I saw both names... I shall wait official designation of rocket for Elektro-L or Spektr-R launches and use Zenit-2SLB for now... -
#134 by anik on 15 Dec, 2007 14:55
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Jim - 15/12/2007 6:37 PM
the 2SLB uses the 3SLB fairings and adapters, which Boeing provides
You did not read this: http://www.sea-launch.com/land-launch/index.html
"In place of the Boeing-made fairing used on Sea Launch, the Zenit-3SLB adopts a 4-meter fairing made by NPO Lavochkin. It is in current production and has been flight-proven with the Block DM. The Zenit-2SLB fairing is an improved version of the heritage Zenit-2 fairing" -
#135 by Jim on 15 Dec, 2007 15:06
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anik - 15/12/2007 10:55 AM
QuoteJim - 15/12/2007 6:37 PM
the 2SLB uses the 3SLB fairings and adapters, which Boeing provides
You did not read this: http://www.sea-launch.com/land-launch/index.html
"In place of the Boeing-made fairing used on Sea Launch, the Zenit-3SLB adopts a 4-meter fairing made by NPO Lavochkin. It is in current production and has been flight-proven with the Block DM. The Zenit-2SLB fairing is an improved version of the heritage Zenit-2 fairing"
oops! I was wrong. I was recalling some old info -
#136 by anik on 19 Dec, 2007 15:36
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anik - 15/12/2007 6:51 PM
QuoteDanderman - 15/12/2007 6:25 PM
what is the difference between the Zenit 2SLB and Zenit 3SLB now described in the launch calendar?
On Novosti kosmonavtiki forum I was told Zenit-2SLB is Zenit with Fregat-SB upper stage and Zenit-3SLB is Zenit with DM-SLB upper stage...QuoteDanderman - 15/12/2007 6:25 PM
Isn't Zenit2-SLB an inappropriate designator, and shouldn't it be "Zenit 2M"?
I saw both names... I shall wait official designation of rocket for Elektro-L or Spektr-R launches and use Zenit-2SLB for now...
According to Novosti kosmonavtiki forum, Zenit with Fregat-SB upper stage will be named Zenit-3SLBF... It is approved already by rocket's manufacturer...
But it is unclear, for now, how Zenit with Fregat-SB will be named officially... -
#137 by William Graham on 19 Dec, 2007 20:30
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Danderman - 15/12/2007 3:25 PM
Isn't Zenit2-SLB an inappropriate designator, and shouldn't it be "Zenit 2M"?
My (limited) understanding of matters is that the 2SLB and 2M are the same rocket, but the 2SLB is the designation used for commercial missions (SL = Sea Launch, parent company of the Land Launch consortium), and 2M for government launches (M=Modernised). Not sure though, can't remember where I read that. -
#138 by sammie on 19 Dec, 2007 22:19
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The 2M and 2SLB are not the same, the former is a 2 stage version used to lift large payloads into LEO, while the latter uses the same first two stages, but a third Block DM-SL to put payloads into GTO. It's just that the Zenit will essentially fly in 4 different versions, a 2 stage version for Russian military, a 3 stage version from Oddesey, and two 3 stage versions from Baikonur. One with a fregat upperstage, the other with a Block DM-SL.
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#139 by Skyrocket on 20 Dec, 2007 05:56
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Following versions of the Zenit are existing or planned
Zenit-2: original two stage land launched zenit
Zenit-2M (governmental flights) = Zenit-2SLB (commercial flights): Two stage version of Zenit-3SLB
Zenit-3SL: Sea launched improved Zenit with Blok-SL upper stage
Zenit-3SLB: land launched version of Zenit-3SL
Zenit-2M Fregat-SB = Zenit-2SLB Fregat-SB = Zenit-3SLBF (?): land launched improved Zenit with Fregat-SB upper stage
