Talk:Space Shuttle Solid Rocket Booster

From Wikipedia, the free encyclopedia

This is the talk page for discussing improvements to the Space Shuttle Solid Rocket Booster article.
Article policies
WikiProject Space
Space Portal
This article is within the scope of WikiProject Space.
Start This article has been rated as start-Class on the assessment scale.
Related projects:
WikiProject Spaceflight WikiProject Spaceflight Importance to Spaceflight: High

This article has been rated but has no comments. If appropriate, please review the article and leave comments here to identify the strengths and weaknesses of the article and what work it will need.
It is requested that a photograph or photographs be included in this article to improve its quality.
The Free Image Search Tool (FIST) may be able to locate suitable images on Flickr and other web sites.

Contents

[edit] "Perforated" as an adjective

According to dictionary.com, "perforated" is an acceptable adjective. One meaning given is "Having a hole or holes, especially a row of small holes." --P3d0 14:36, Jan 31, 2005 (UTC)

[edit] Give Source

I was surfing the NASA website when I found this article (almost word for word) in the NASA NSTS 1988 News Reference Manual http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/stsref-toc.html I realize it is probably public domain, but seeing as how this article is essentially copy-and-pasted straight from the NASA manual, I think a little credit is due.68.117.57.158 06:53, 1 August 2005 (UTC)

I did a little more digging and found that the copy-and-pasting first appeared in Theon's edit (17:11, 17 June 2004)-not that it makes much difference (sorry if I'm going about this the wrong way-it is the first time I have ever written on wiki) 68.117.57.158 07:00, 1 August 2005 (UTC)

[edit] The O-rings

It seems perverse in this otherwise very informative article, not to mention either a) The construction of the boosters out of a number of segments joined together with sophisticated double O-ring seals or b) The fact that it was the failure of one of these seals that was directly responsible for the Challenger disaster - particularly, since the latter incident and some of the changes that resulted are detailed in the article. My knowledge is limited to what can be found on the web - and elsewhere in Wikipedia - nevertheless, I have included a modest section on the O-ring sealed construction. I invite others with more knowledge to edit and expand this. Peter M 18:43, 9 October 2005 (UTC)

Nice pictures of original and new joint are here: http://history.nasa.gov/rogersrep/v6ch1.htm, http://history.nasa.gov/rogersrep/v6p14.htm, http://history.nasa.gov/rogersrep/v6p15.htm —The preceding unsigned comment was added by 195.212.29.187 (talk) 13:46, 28 December 2006 (UTC).

[edit] Saturn V and other statements

The shuttle does not have more liftoff thrust than the Saturn V. The 3.3 million lbs (takeoff) thrust figure for the SRB is wrong -- it's vacuum thrust. SRB sea level takeoff thrust is considerably less. Joema 01:22, 8 February 2006 (UTC)

Comment: If you are using that STS-107 graph as proof, then the shuttle reaches as much or more than 3.2 million at sea level. In addition, I have cited below two NASA links which (and they have updated it in the past year) to say 3.3 million sea level specifically. The shuttle produces nearly the same, not much less, than the Saturn V. User CapeCanaveral321.

Also the SRB does not require most of the thrust to reach orbit. Joema 01:22, 8 February 2006 (UTC)

Well, they provide most of the thrust, and also most of the integral over time of thrust- the impulse. WolfKeeper 04:58, 8 February 2006 (UTC)
Actually the SSMEs provide most of the impulse. The SRB average vacuum thrust over the 120 sec. firing period is 2.395 million lbs, for a total impulse of 574.8 million lb-sec. The SSME vacuum thrust is about 500,000 lb per engine, total 1.5 million lbs, total impulse over 8.5 minutes (510 sec) is 765 million lb-sec. Thus the SSME total impulse is considerably greater than SRB total impulse.
The SSMEs are highly optimized for vacuum thrust since most of their firing duration is in vacuum. The SRBs are more optimized for sea level thrust, but their vacuum thrust is still higher, but less increase than the SSMEs. When comparing SSME vs SRB total impulse we must use the thrust figure where each engine spends most of its time. By contrast when comparing liftoff thrust, we must use SRB sea level vs SSME sea level thrust; but that's not the point here. You can see a thrust/time graph of SRB sea level thrust on page 182, figure 3-33 at: [1] (warning, large PDF). There's a thrust/time graph for SRB vacuum thrust on page 8 of this document: [2] Joema 14:09, 8 February 2006 (UTC)

Most of the total delta V energy is from the SSMEs, not the SRB.Joema 01:22, 8 February 2006 (UTC)

I don't know, I've never worked it out. Energy is a funny thing in a rocket. You need to take into account the fact that quite a lot of the kinetic energy of the liquid hydrogen propellant is put there by the SRBs. It all gets very messy very quickly. And the delta-v due to the SRBs is surprisingly high after you account for atmospheric losses and gravity losses. But that wasn't what the piece said anyway.WolfKeeper 04:58, 8 February 2006 (UTC)
As the above shows the SSMEs provide more of the total impulse, hence more of the energy to reach orbit. You're right due to K=1/2m^v2, the SRBs have imparted a lot of energy despite the low staging velocity since vehicle mass is so great at that point. However the total energy imparted by the SSMEs is significantly greater. Joema 14:09, 8 February 2006 (UTC)

The SRBs do supply over 70% of the initial liftoff thrust, so revised wording to state that. Joema 01:22, 8 February 2006 (UTC)

[edit] SRB thrust graph

I'm confused about exactly what the thrust graph is showing. Is this predicted/design thrust, or measurements from an actual mission? I'm guessing the latter, since there are distinct left/right values and I would assume they are designed to be identical. Also, I don't understand what it means to talk about "sea level thrust" at various time points into the mission. It's obviously not at sea level except at t=0. What does sea level thrust at t=60 mean? -- RoySmith (talk) 23:41, 2 March 2006 (UTC)

Roy, good questions. Yes it's actual thrust data from the Columbia mission, STS-107. However you can't directly measure thrust. Rather it's calculated from other parameters such as chamber pressure. Also the thrust curve is generally corrected to constant sea level or constant vacuum thrust. In actuality the physical thrust would be continuously changing from altitude variation, even if engine design thrust was constant (which it's not for the SRBs). I include below some more info I was preparing to post:
Because of the frequent confusion on this point, I uploaded a thrust/time graph for the SRBs. I also revised the thrust numbers in the article to reflect this. SRB sea level liftoff thrust is 2.8 million pounds each. Each SSME produces 393,000 pounds sea level thrust at 104% power level. Thus the shuttle total liftoff thrust is: (393,000 * 3) + (2,800,000 * 2) = 6.779 million pounds force, or 3.075 million kgf, or 30.16 MN. Using these numbers the SRBs provide 82.6% of liftoff thrust.
This is confusing because many sources just blindly copy the 3.3 million pound thrust number, some even erroneously adding "sea level" or "liftoff" thrust. There are six possible thrust numbers for the SRB:
  • Sea level liftoff thrust
  • Sea level peak thrust
  • Sea level average thrust
  • Vacuum liftoff thrust
  • Vacuum peak thrust
  • Vacuum average thrust
The problem is most references don't state which they are using. This is why references state SRB thrust from 2.65 million lbs (probably sea level average thrust) to 3.4 million lbs (probably vacuum peak thrust).
When comparing SRB thrust to, say, Saturn V F-1 engine thrust, you must consider the different characteristics of each engine type. The F-1 is not throttlable, so excluding altitude variations always produces the same thrust. At sea level this is 1.5298 million lbs per engine or 7.649 million lbs thrust total. By comparision the SRB thrust changes over the burn time (see chart). Space shuttle total sea level liftoff thrust is 6.779 million pounds force, or about 88.6% of the Saturn V.
In theory you could compare the SRB thrust at T+20 sec which is somewhat higher, but that wouldn't be liftoff thrust. Joema 23:57, 2 March 2006 (UTC)

[edit] Comment on changes

User:Simon Dodds last edit was correct: the correct SRB relative thrust contribution is 83%. Each SRB produces 2.8 million lbf sea level liftoff thrust. Each SSME produces 393,800 lbf sea level liftoff thrust. Thus we calculate: (2.8 million * 2) / ((2.8 million * 2) + (393,800 * 3)) = 82.578%

For more info on SSME thrust, see the specs I added to that article.

Other changes:

  • Deleted 83% SRB thrust contribution during 1st stage. Reason: unverified and unlikely, since SRB sea level thrust profile changes over time. See SRB thrust graph.
  • Improve wording of SRBs constituting 80% of liftoff mass. Joema 12:43, 12 April 2006 (UTC)

Update based on the discussion above: According to NASA and ATK, the sea level thrust of the SRB is 3.3 million with an average of 2.6 over the duration of the burn. Where does the 2.8 number come from? In addition, for anyone using Astronautix as a source, their numbers are incorrect.

http://www.spaceflight.nasa.gov/shuttle/reference/shutref/srb/srb.html http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/srb.html http://www.atk.com/Customer_Solutions_LaunchSystems/cs_ls_hsf_ssrsrm.asp

It is my opinion, and based on the graph of performance of STS-107, that the article should state that they produce a maximum sea level thrust of 3.3, with a liftoff thrust of 2.8 increasing through the first 20-25 seconds of flight, and that a typical mission (cited 107 graph) produces about 3.2 at sea level.

Just for an aside, if someone who is attending a launch wants to know what they are going to feel and hear, they should know that they will feel and hear 3.2-3.3 million.

[edit] SRB vs SRM

I believe that 'Solid Rocket Motor' (SRM) refers solely to the actual solid motor inside the booster, whereas 'Solid Rocket Booster' refers to the whole assembly including the casing, nozzle, parachutes, etc. I've been trying to find a definitive reference on this, but none of the obvious places (e.g. Shuttle News Reference) seem to have one. Mark Grant 20:35, 14 July 2006 (UTC)

Yep. In Booster Systems Briefs, Final, Rev F, JSC-19041, it states:
The solid rocket booster (SRB) element of the space shuttle (Figure 4.1-I) is made up of six subsystems:
  • The solid rocket motor
  • The structural subsystem
  • The thrust vector control subsystem
  • The separation subsystem containing mechanical and ordnance equipment
  • The recovery subsystem containing mechanical and parachute equipment
  • The electrical subsystem
Cjosefy 20:53, 14 July 2006 (UTC)

[edit] New expanded image

I think this page my benifit from a different expanded iamge of the SRB. Perhaps this one will do (in JPG and PNG):

Nice diagrams, one of them should be included to replace the existing image, but there is a note missing from the "Forward Skirt and Forward IEA"; there is an arrow below it with no note attached. Peter Maggs 07:41, 15 July 2006 (UTC)
It was missing in the source document. I've edited out the arrow.Cjosefy 21:02, 19 July 2006 (UTC)
I replaced the old diagram. Please check it out and make sure it is ok. Cjosefy 21:05, 19 July 2006 (UTC)

Image:SpaceShuttleSolidRocketBooster.png Cjosefy 21:06, 14 July 2006 (UTC)

[edit] Thrust?

So is there a definitive source for the SRB thrust figure? The cites given in the recent edit do say it's 3,300,000lbs, but that's obviously directly contradicted by the STS-107 thrust graph. I'd tend to believe the latter, but it's odd that NASA sites give the former. Mark Grant 02:16, 3 May 2007 (UTC)

Reply by CapeCanaveral321 02:20 3 May 2007 UTC. First let me note that based on my visits to those reference manuals, NASA has added the words sea level there in the past year or even months. That may be based on discussions here or on certain web forums. It is not out of the question that they see our questions and added that.

This does not directly contradict the STS-107 graph. The graph shows 3.2 million at T+20 which is sea level for all that matters. 3.3 is probably the maximum it can reach at sea level and I would guess it has on some missions of in testing as they would not cite the number otherwise. SRB segments are poured and used in specific sets, and each set is tailored for a specific mission requirement.

[edit] Reusable Solid Rocket Motor (RSRM)

The article uses the acronym RSRM, which is presumably "Reusable Solid Rocket Motor". But it never defines the term. Is it a synonym for SRB? Is the motor some subset of the entire booster? If so, and given the diagram in the article doesn't show it, can anyone add some explanatory text? (Sdsds - Talk) 03:22, 4 May 2007 (UTC)

I think it's Redesigned solid rocket booster, but I'd need to check. --GW_SimulationsUser Page | Talk 21:25, 4 May 2007 (UTC)
You are correct, as confirmed by ORBITER MANUFACTURING AND ASSEMBLY. NASA.. (sdsds - talk) 07:18, 14 June 2007 (UTC)
The most common use of RSRM is reusable solid rocket motor, NOT redesigned. This includes many thousands of references within recent NASA documentation. However both forms -- reusable and redesigned -- are very common. For the sake of consistency I suggest we use the most common version -- reusable -- but explain that both nomenclatures are common and either is proper.
Re the other point about RSRM vs SRB, yes we should make that clear. In general popular usage, both RSRM and SRB are commonly used interchangeably. However, technically RSRM refers to the solid fuel and nozzle, whereas SRB refers to the entire structural assembly (which includes avionics, parachutes, and structural support hardware). Joema 11:59, 14 June 2007 (UTC)

[edit] Citations missing

There is a note near the bottom saying that most of the text comes from NASA, this is fine but the source on the nasa website or reference. Anynobody 00:44, 6 May 2007 (UTC)

[edit] Seven segment vandalism?

This edit in 1995 added the text, "The boosters are assembled from seven individually manufactured segments." Where did that come from? Why, with all the talk of four segment and future five segment SRBs, do we claim there are seven segments? Or does "segments" in this context perhaps refer to something else entirely? (sdsds - talk) 08:20, 21 November 2007 (UTC)


[edit] SRB separation image

The image is a faked photo-manipulation, so doesn't belong in an encyclopedia. This is obvious for several reasons:

(1) In general, there is no ground-based or aerial imagery of that clarity. Here is a typical ground-based image of the same separation event: [3]. However after the loss of Columbia, STS-107, specialized high-altitude aircraft with high-resolution imaging devices track each launch. Here is video from one launch: [4]

(2) The windstream effects on the separation motor exhaust isn't depicted. At SRB sep, the vehicle is 150,000 ft. altitude, moving at Mach 4 (about 3,000 mph). Atmospheric dynamic pressure is fairly low -- about 0.25 pounds per square foot. However this is sufficient to immediately deflect rearward the lateral-firing separation motor exhaust. However the image doesn't show this. By contrast see actual on-board video of the separation event (happens at 2 min. into this video): [5]. Also note the same effects in the above video taken from a high-altitude aircraft. Joema (talk) 11:53, 25 April 2008 (UTC)

[edit] Information to be added

The steel case segment from the SRB is made by different forming manufacturing processes. These are starting from As-cast blank, reverse extruding, ring rolling and roll forming. The steel used is D6AC steel.

The case segments are about 3 m diameter and about 13 mm thick. Tolerance from ticknest is 0.25 mm.

From metal ingot to actual cylinder are applied in order. upsetting, extrusion, ring rolling, roll forming, machining and heat treating.

Source: Kalpakjian S and Schmid S. R. Manufacturing engineering and technology, 5th edition. Pearson Prentice Hall. USA, 2006. ISBN 0-13-148965-8 —Preceding unsigned comment added by Gengiskanhg (talk • contribs) 14:56, 6 June 2008 (UTC)