Author Topic: Sierra Nevada’s 5-year partnership with NASA - Progress on Dream Chaser  (Read 27786 times)

Offline Jim

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Proper engineering? Is it not proper engineering when a spacecraft temporarily modifies its pressure vessel by attaching a space station or another spacecraft to it?

The basic vessel integrity is not changed.

Offline BrightLight

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Proper engineering? Is it not proper engineering when a spacecraft temporarily modifies its pressure vessel by attaching a space station or another spacecraft to it?

The basic vessel integrity is not changed.
I too was not surprised to hear that the entire LIDS was to be replaced after each use.
In aircraft payloads that I have some familiarity with for gas of liquid transfer, there are generally three types of connectors that I have used - permanent connections not to be broken until dis-assembly, O-ring class connections for periodic transfers and connectors that are used once with crushable gaskets that are thrown away to be replaced for the next use.
It is not unusual to throw away O-rings as well, depending on the requirements of the mission.
The LIDS engineering requirements might be stringent enough that the cost for testing/verifying the various components might be more expensive then building whole new systems. Good engineering and cost management practices would evaluate these costs and develop a maintenance conops accordingly - from what SNC has said (quoted) it is cheaper to replace the LIDS then to re-manufacture, I have no reason to doubt the analysis.

Offline A_M_Swallow

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LIDS is a doorway.  How often do doors get thrown away after a single use?

Offline Lee Jay

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LIDS is a doorway.  How often do doors get thrown away after a single use?

Every Soyuz and Progress launch?

Offline BrightLight

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LIDS is a doorway.  How often do doors get thrown away after a single use?
LIDS is as much a doorway as the Chunnel is a hole in the ground.
LIDS from my limited physics/Engineering perspective is- amongst other things- a pressure vessel interconnect, and as such must maintain the gas pressure between the two vessels when engaged.  The gaskets in LIDS must deform enough to create a tight (there must be an engineering requirement for leak rates) seal between the spacecraft and the ISS. Being that I don't have the engineering requirements for connecting to the ISS I will assume here that the seal has to perform at a level that makes the LIDS a costly device to build and validate.

Offline BrightLight

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LIDS is a doorway.  How often do doors get thrown away after a single use?

Every Soyuz and Progress launch?

Thank you Lee Jay.
How did the Shuttle connection work, did the refurbishment require extensive re-build or did USA build new connectors for every launch?

Offline pathfinder_01

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LIDS is a doorway.  How often do doors get thrown away after a single use?

Most doorways don't have to be protected from harsh enviroments. If dreamchaser had a cargo bay like the shuttle it would make sense to reuse, but hanging outside like that, it maybe better to discard.
« Last Edit: 06/25/2012 12:08 AM by pathfinder_01 »

Offline clongton

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LIDS is a doorway.  How often do doors get thrown away after a single use?

Most doorways don't have to be protected from hash enviroments. If dreamchaser had a cargo bay like the shuttle it would make sense to reuse, but hanging outside like that, it maybe better to discard.

Isn't that essentially what Elon said? That it was less expensive to replace than refurbish?
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Offline BrightLight

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LIDS is a doorway.  How often do doors get thrown away after a single use?

Most doorways don't have to be protected from hash enviroments. If dreamchaser had a cargo bay like the shuttle it would make sense to reuse, but hanging outside like that, it maybe better to discard.

Isn't that essentially what Elon said? That it was less expensive to replace than refurbish?
I thought so too, but I can't find the post that quotes Elon as saying that, Is there a post or statement from Boeing on how they intend to deal with LIDS on the CST-100?

Offline Lee Jay

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LIDS is a doorway.  How often do doors get thrown away after a single use?

Every Soyuz and Progress launch?

Thank you Lee Jay.
How did the Shuttle connection work, did the refurbishment require extensive re-build or did USA build new connectors for every launch?

I don't know about how much refurb got done, but I'm reasonably confident that the ODS wasn't replaced after each flight.

Offline erioladastra

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LIDS is a doorway.  How often do doors get thrown away after a single use?

Most doorways don't have to be protected from hash enviroments. If dreamchaser had a cargo bay like the shuttle it would make sense to reuse, but hanging outside like that, it maybe better to discard.

Isn't that essentially what Elon said? That it was less expensive to replace than refurbish?
I thought so too, but I can't find the post that quotes Elon as saying that, Is there a post or statement from Boeing on how they intend to deal with LIDS on the CST-100?

CST-100 uses careful arrangement and a forward heat shield.

Offline Orbital Debris

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LIDS is a doorway.  How often do doors get thrown away after a single use?

Every Soyuz and Progress launch?

Thank you Lee Jay.
How did the Shuttle connection work, did the refurbishment require extensive re-build or did USA build new connectors for every launch?

I don't know about how much refurb got done, but I'm reasonably confident that the ODS wasn't replaced after each flight.
Seals were replaced after every 3rd flight.  Test, teardown and  inspection with minimal parts replacement during OMDP (~10 flights).  However, the ODS was enclosed by the payload bay doors and not subjected to a possible plasma environment. 

Offline Orbital Debris

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LIDS is a doorway.  How often do doors get thrown away after a single use?

Most doorways don't have to be protected from hash enviroments. If dreamchaser had a cargo bay like the shuttle it would make sense to reuse, but hanging outside like that, it maybe better to discard.

Isn't that essentially what Elon said? That it was less expensive to replace than refurbish?
I thought so too, but I can't find the post that quotes Elon as saying that, Is there a post or statement from Boeing on how they intend to deal with LIDS on the CST-100?

CST-100 uses careful arrangement and a forward heat shield.

CST-100 was baselined as APAS, with possible replacement with NDS (NASA docking system) depending on development schedules.  The fwd heat shield protects the Navigation and Rendezvous sensors.  CST does not plan on major refurbishment of the APAS between flights.

Offline lesxiarxis

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Atlas 4xx has a limit of about 20,000 lbs for payload. Does the DreamChaser really have such a low weight?
The DC might not actually have such a low weight. There are several factors that could benefit the (required) performance.
- No payload faring, reducing weight on the Atlas.
- Altlas 402 (x02?), not the 401 we are used to. Better performance to LEO because of the dual engine Centaur.
- DC might do an OMS-2 or even an OMS-1 style burn, lowering the dV requirement on the Atlas.

Its a structural loads issue, not a payload performance issue. Atlas 4xx actually can orbit more mass than it can lift with 2 RL-10s in the Centaur.


According to the document atached, p14, table 1, the 402 can lift 27,558 lb at an inclination of 28.5°, 185 km circular orbit

http://www.faa.gov/about/office_org/headquarters_offices/ast/media/ast_developments_concepts_2010.pdf

Offline erioladastra

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LIDS is a doorway.  How often do doors get thrown away after a single use?

Most doorways don't have to be protected from hash enviroments. If dreamchaser had a cargo bay like the shuttle it would make sense to reuse, but hanging outside like that, it maybe better to discard.

Isn't that essentially what Elon said? That it was less expensive to replace than refurbish?
I thought so too, but I can't find the post that quotes Elon as saying that, Is there a post or statement from Boeing on how they intend to deal with LIDS on the CST-100?

CST-100 uses careful arrangement and a forward heat shield.

CST-100 was baselined as APAS, with possible replacement with NDS (NASA docking system) depending on development schedules.  The fwd heat shield protects the Navigation and Rendezvous sensors.  CST does not plan on major refurbishment of the APAS between flights.

CST is now baselined for NDS.

Offline Robotbeat

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I read another article that said the Dream Chaser was going to have thousands of tiles.  It doesn't seem like it is going to be very cost efficient totally replacing all damaged tiles, even if only scratched.

Remember DC is many times smaller than Shuttle (as my visit yesterday to Udvar Hazy drove home in abundance).
...
Quite a good point. Even with identical tiles, servicing the TPS on Dreamchaser should be at least an order of magnitude easier. And because Dream Chaser is much smaller and just getting started now, they can improve the techniques, perhaps build a better version of Dream Chaser later on (with larger tiles for less servicing? even a totally different TPS concept?) with improved turnaround capability.

I don't really buy a lot of the advantages of Dream Chaser, but its reusable TPS is potentially a significant advantage.
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Offline Ronsmytheiii

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Quite a good point. Even with identical tiles, servicing the TPS on Dreamchaser should be at least an order of magnitude easier. And because Dream Chaser is much smaller and just getting started now, they can improve the techniques, perhaps build a better version of Dream Chaser later on (with larger tiles for less servicing? even a totally different TPS concept?) with improved turnaround capability.

I don't really buy a lot of the advantages of Dream Chaser, but its reusable TPS is potentially a significant advantage.


I was under the impression that Dreamchaser used a heat shield "shoe" that uses an ablative substance:

"Every vision is a joke until the first man accomplishes it; once realized, it becomes commonplace." - Robert Goddard

Offline Robotbeat

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Quite a good point. Even with identical tiles, servicing the TPS on Dreamchaser should be at least an order of magnitude easier. And because Dream Chaser is much smaller and just getting started now, they can improve the techniques, perhaps build a better version of Dream Chaser later on (with larger tiles for less servicing? even a totally different TPS concept?) with improved turnaround capability.

I don't really buy a lot of the advantages of Dream Chaser, but its reusable TPS is potentially a significant advantage.


I was under the impression that Dreamchaser used a heat shield "shoe" that uses an ablative substance:



I was under the impression that it largely used reusable tiles. Certainly the hottest parts (if not ablative) would be RCC pieces (really expensive, but can be in single large pieces and should be reusable...).

I must admit the impression was formed quite a while ago and things may have changed.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Ronsmytheiii

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I was under the impression that it largely used reusable tiles. Certainly the hottest parts (if not ablative) would be RCC pieces (really expensive, but can be in single large pieces and should be reusable...).

I must admit the impression was formed quite a while ago and things may have changed.

Edit: at 39:57 the TPS is an ablative on tile system developed by Ameas that will be replaced as a whole rather than tile by tile, and will be replaced periodically rather than mission by mission.
« Last Edit: 06/27/2012 01:21 AM by Ronsmytheiii »
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Offline Go4TLI

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The TPS uses an evolved design from orbiter. There is no RCC, nor does there need to be.

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