Hubble DeOrbit Module

[mrmorris]

Soooo.. the Aug 22nd Astronotes title indicates that NASA has decided against a de-orbit module for Hubble. However, the quote they have from "Chris Shank, special assistant to NASA chief, Michael Griffin", seems to indicate that he's somewhere between confused and clueless. Specifically:<br /><br /><i>"It does not look like a propulsion module will be necessary for a shuttle servicing mission,"</i><br /><br />The servicing mission was <b>never</b> going to include a de-orbit module. The orbiter doesn't have the lift capacity to take one up to the Hubble's orbit. So... has the robotic DO mission truly been cancelled, or is Chris simply out of the loop?

 

[shuttle_rtf]

Good question! The focus has been drawn away from HSM (3?) seen as the fleet's not yet flying on a regular basis yet.<br /><br />The last comments on this from Griffin were ambiguous at best.<br /><br />Maybe it's popped up on something SG's recieved...I'll ask around too.

 

[tap_sa]

<font color="yellow">"The servicing mission was never going to include a de-orbit module. The orbiter doesn't have the lift capacity to take one up to the Hubble's orbit."</font><br /><br />Woot? The shuttle can lift the Hubble itself to the orbit but cannot deliver a module that would impart around 100m/s deltaV to the telescope? That's some DO, />11 tonnes of whatnot. Or is the plan to break all horisontal speed and let it drop like a rock <img src="/images/icons/smile.gif" />

 

[mrmorris]

<font color="yellow">"The shuttle can lift the Hubble itself to the orbit but cannot deliver a module..."</font><br /><br />OK -- now I am confused. S_G has indicated previously (or possibly I'm misremembering) that the shuttle doesn't have the capacity to put a DO module up on the 'indefinite' servicing mission. I had thought (and almost posted in this reply... before I changed my mind and did some research) that the shuttle had deployed Hubble to a lower orbit and a secondary propulsion stage had lifted it to its working orbit. Since that's not the case -- I'd have to say... heckifIknow.

 

[mrmorris]

<font color="yellow">"I thought the plan was to reservice and add the DO module on the same flight. "</font><br /><br />Dunno then. I know there've been many posts in the past about the Hubble orbit being at the edge of the orbiter's envelope. Checking out the Servicing mission info from NASA though, there's no mention of adding a de-orbit module during SM4:<br /><br /><i>"Possible Future Servicing<br />The last originally planned Shuttle servicing mission to Hubble-known as "SM4"-was cancelled in January, 2004 due to concerns of astronaut safety in the wake of the Columbia Shuttle tragedy in February of 2003. For essentially the remainder of 2004 and extending into early-2005, NASA and the HST Program performed studies and early planning for a possible robotic servicing mission that, if successfully executed, would have achieved all of the primary SM4 goals. These included the installation of six fresh gyros, six new batteries, a fine guidance sensor, and two advanced science instruments, known as the "Cosmic Origins Spectrograph" (COS) and the "Wide-Field Camera 3" (WFC3). The goal of either type of servicing mission-Shuttle or robotic-was to extend Hubble's science life by at least five years and to bring critical new scientific capabilities to the telescope."</i><br /><br />The Shuttle Press Kit here indicates the same thing, and says there was to be a 'closeout' mission after SM4:<br /><br /><i>"Closeout Mission -- 2010 <br /><br />NASA will determine the best approach to secure the Telescope, upon the completion of Hubble's 20-year mission. Currently there are several options being considered, ranging from staying in orbit indefinitely through a large reboost, to a return to ground."</i>

 

[mrmorris]

<font color="yellow">"No, that was not me. ..."</font><br /><br />Sorry to come back at ya, SG... but this has been bugging the heck out of me. My memory isn't infallible... but it's normally pretty good for factoids of interest to me. I did a search to find the post from you that indicated the shuttle was low on performance for the DO module:<br /><br /><i>1207: "HELLO.... the shuttle would likely be able to attach the deorbit booster along with the $200 million dollars worth of equipment already manufactured for the Hubble. "<br /><br />shuttle_guy: "No the Shuttle servicing mission does not have the performance margin to also have the deorbit module in it's payload. "</i>

 

[shuttle_man]

"Closeout Mission -- 2010"<br /><br />Correct.

 

[Testing]

Some one or some thing is planning to go to Hubble as our part of WFC3 is back in house getting upgraded optical filters and it was delivered in 2002. <div class="Discussion_UserSignature"> </div>

 

[mrmorris]

So which is correct? Does the Orbiter have the performance margin for the DO module or does it not?<br /><br />As Tap_Sa indicated -- if Discoverer got Hubble itself up there at ~11,000 kg, it would seem that the mass of a few instruments should leave plenty of uplift capacity for a reasonable DO module. I did a couple of quickie-calcs on the mass of a solid to get 100m/s dv (assuming Tap_Sa's number was correct) and the results were nowhere close to what I would think of as an upper limit for sucha module.<br /><br />On the other hand -- a deorbit module that would be intended to make a <b>controlled</b> re-entry for Hubble would likely require liquid propellants. I beleive after Challenger that liquid props in the cargo bay were ruled out.

 

[CalliArcale]

No, you can do a controlled reentry with solids. That's actually the plan for CRV (if it ever gets revived). <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[tap_sa]

<font color="yellow">" solid to get 100m/s dv (assuming Tap_Sa's number was correct) "</font><br /><br />Didn't calculate it but NASA quotes orbiter's deorbit delta-v to be 300fps. Rounded it upward to a metric ballpark since Hubble is higher than usual Shuttle orbits.<br /><br />Btw what if you skip rockets and use a terminator tether?

 

[mrmorris]

<font color="yellow">"Didn't calculate it..."</font><br /><br />I can't claim expertise on my dv calculations -- not really my thing. However, if my numbers were correct (<b>big</b> if) -- it could have been 200-300 m/s and still not been half the mass of the Hubble.

 

[krrr]

To decelerate HST by 100 m/s, less than 400 kg of solid propellant would be needed.

 

[mrmorris]

<font color="yellow">"...less than 400 kg ..."</font><br /><br />Ayup -- that's about what I came up with -- using iSP of the SRBs (~230). Seemed lowish, so I didn't trust (or post) it. If valid -- there should be ample lift capability in the orbiters to get a DO module up there.<br /><br />S_G -- since it doesn't appear to be mass or payload (i.e. liquid booster) restrictions -- could it simply be a man-handling restriction? While the orbiters may have ample lift to take a ~600kg (w/nozzles, casing, etc.) DO booster to the Hubble orbit, astronauts still have to manhandle the booster into place. Since the robotic arm can hold either the Hubble or the booster, but not both -- that means some free-flying going on near the orbiter with a heavy weight. Dangerous to the 'nauts, the orbiter and Hubble itself.

 

[nyarlathotep]

Surely the ProSEDS hardware is still lying in a storeroom somewhere. Just take up the 25kg tether, a pack of electrical tape and a set of wirecutters, and bolt it onto hubbles solar array.

 

[mrmorris]

<font color="yellow">"This could be done."</font><br /><br />OK -- then I'm officially out of ideas. Presumably:<br /><br />- The orbiters have the lift capacity to take a DO booster up.<br />- An allowable (solid) booster can be used for the deorbit.<br />- It's possible (albeit potentially tricky) for the 'nauts to install the DO booster.<br /><br />So why would SM4 *not* be taking up a DO booster, thereby saving a few hundred million dollars from having to develop a dedicated DO robotic mission? Anyone? Bueller? Bueller?

 

[mrmorris]

<font color="yellow">"One reason may be that the DO does not exist..."</font><br /><br />I can't see that as a reason -- or at best a pretty weak one. How long has SM-4 been scheduled? The shuttle manifest document I linked to earlier was made right after SM-3A in December 2000 and SM-4 was scheduled for 2003 at the time so they had <b>at least</b> 3 years of lead time -- probably a good bit more. No one looked at the manifest for SM-4 and conected the dots between the thoughts of: 'Hey -- we have ~8,000 kg of uplift capacity' and "Hey -- Hubble's going to need a DO booster". <br /><br />Thiokol STAR boosters of that class already exist, so it'd just be a matter of putting together the avionics and frame (w/Hubble attach points). They likely had a five-year lead time or more on speccing out the SM-4 mission. If they had time to develop the instruments for SM-4, they had time to develop a DO booster.

 

[nyarlathotep]

Does it even need a deorbit burn? Why cant we just let it crash somewhere in Perth like skylab?<br /><br />Surely selling the wreckage on ebay alone could compensate for the damage.

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>Does it even need a deorbit burn? Why cant we just let it crash somewhere in Perth like skylab?<p><hr /></p></p></blockquote><br /><br />Because it's pure luck that Skylab didn't hit anybody. NASA doesn't want to take the risk of killing somebody when they could be much more responsible and deorbit the thing in a controlled fashion. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[nyarlathotep]

Bah, this silly risk adverse culture is ruining NASA. The odds of a piece hitting someone are worse than Powerball.