Author Topic: Long March 2F booster and first stage burn time Wikipedia vs seen video.  (Read 1595 times)

Offline markbike528cbx

  • Full Member
  • *
  • Posts: 162
  • The Everbrown portion of the Evergreen State
  • Liked: 143
  • Likes Given: 88
I was watching the Shenzhou 17 launch on the Long March 2F  booster.
I had consulted the Wikipedia page https://en.wikipedia.org/wiki/Long_March_2F.
Wiki states that the burn time of the boosters was 128 seconds and the first (core) stage was 166 seconds.

I was worried when I saw the boosters and 1st stage core both shut down and separate at  158 seconds.

The Shenzhou 14, 15, 16 and 17 launches all had similar booster and core first stage shutdown and separation times.

O no, Wikipedia is wrong?  I also note that everyday astronaut website also has similar values to Wikipedia.

Since Long March 2F is exclusively used for Shenzhou launches, what would the reason for the apparent inaccuracy be?
Differences in MaxQ thrust bucket (if applicable)? 

As a side question, I note that the launch escape system is jettisoned quite early (before booster, 1st core stage burnout).
I guess if they stopped/blew up, then a capsule simple separation would be sufficient?


Offline edkyle99

  • Expert
  • Senior Member
  • *****
  • Posts: 15431
    • Space Launch Report
  • Liked: 8616
  • Likes Given: 1362
Part of the problem is that China has not released a CZ-2F "User's Guide", but did previously (in 1999) release one for CZ-2E, upon which CZ-2F is based.  The CZ-2E manual showed staggered cutoff times for the boosters and first stage (139 seconds for the boosters, 158 seconds for the first stage).  The CZ-2F setup likely changed to reduce dynamic loads, g-forces, etc. during ascent for the Shenzhou spacecraft and their abort systems.  The CZ-2F boosters apparently were stretched slightly to carry more propellant than the CZ-2E boosters, allowing for  their longer burn times. 

 - Ed Kyle
« Last Edit: 10/30/2023 07:06 pm by edkyle99 »

Offline markbike528cbx

  • Full Member
  • *
  • Posts: 162
  • The Everbrown portion of the Evergreen State
  • Liked: 143
  • Likes Given: 88
Thanks Ed Kyle.
Makes sense. 
The 2F being Shenzhou only would mean that there is no incentive to have a users manual for external use. 
Any thoughts on what seems to me to be a early jettison of the Launch Escape System?

Offline edkyle99

  • Expert
  • Senior Member
  • *****
  • Posts: 15431
    • Space Launch Report
  • Liked: 8616
  • Likes Given: 1362
Any thoughts on what seems to me to be a early jettison of the Launch Escape System?
These escape systems are designed to work during ascent while still in the atmosphere.  They are jettisoned above about 80 km or more, typically.  Soyuz jettisons its escape system a bit more than 2.5 minutes after launch.  Saturn IB/Apollo jettisoned at 84 km at T+2:43.  Perhaps CZ-2FG has better T/W during its early ascent and gets into near-vacuum a bit quicker.  Once the escape tower departs, Shenzhou would be protected with additional abort modes.

Also, FYI, there have been four CZ-2F launches without a Shenzhou payload, identified as CZ-2FT.  There were two space station module launches and two reentry test spaceplane launches.  The upgraded CZ-2FG began flying with Shenzhou 8.

 - Ed Kyle
« Last Edit: 10/30/2023 10:38 pm by edkyle99 »

Offline oscar56

  • Member
  • Posts: 1
  • Washington
  • Liked: 0
  • Likes Given: 0
Part of the problem is that China has not released a CZ-2F "User's Guide", but did previously (in 1999) release one for CZ-2E, upon which CZ-2F is based.  The CZ-2E manual showed staggered cutoff times for the boosters and first stage (139 seconds for the boosters, 158 seconds for the first stage).  The CZ-2F setup likely changed to reduce dynamic loads, g-forces, etc. during ascent for the Shenzhou spacecraft and their abort systems.  The CZ-2F boosters apparently were stretched slightly to carry more propellant than the CZ-2E boosters, allowing for  their longer burn times. 

 - Ed Kyle
The change to the CZ-2F's installation was likely done to improve mission safety.
When you look at the stars, you realize how small a person is in this huge world.
  kazecon

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
0