Sierra Nevada’s 5-year partnership with NASA - Progress on Dream Chaser

[Chris Bergin]

Another Dream Chaser article! This time Chris Gebhardt has written up some of the latest and some of our content via Lee Jay's visit to SNC:

http://www.nasaspaceflight.com/2012/06/sierra-nevadas-5-year-partnership-nasa-progress-dream-chaser/

[AndrewSTS]

Awesome! This site's really covering this vehicle really well!

[yg1968]

Thanks. Good article.

I have one question about this paragraph:

Even more impressive is the seeming lack of modifications needed to the Atlas V’s ground equipment currently in use by United Launch Alliance. In fact, Sierra Nevada indicates that only an adaptor to the current launch tower would be needed for vehicle access – both for the crews of Dream Chaser and support personnel who would assist astronauts with entry into the vehicle and final preparations for launch.

Wouldn't you need a pad with crew ingress/egress as explained by Gass on page 8 of the ULA presentation at the Augustine Committee?   

Human rating impacts to flight-proven existing EELV
are understood
– Addition of an Emergency Detection System (EDS)
– Separate VIF/MLP or pad with crew ingress/egress

Low non-recurring ($400M) and recurring costs
($130M/launch)

http://www.nasa.gov/pdf/361835main_08%20-%20ULA%20%201.0_Augustine_Public_6_17_09_final_R1.pdf

See also p. 5 of this ULA document:
http://www.ulalaunch.com/site/docs/publications/AtlasDeltaCrewLaunch2010.pdf

[ginahoy]

Moreover, the vehicle’s docking adapter will be removed and replaced after each mission instead of being reused.

According to Mark Sirangelo, “The economics work out that it’s not really advantageous to reuse it.”  This goes toward an explanation for why there is no body flap on the back of Dream Chaser, like there was on Shuttle, to protect Dream Chaser’s docking adaptor.

I thought the purpose of the Shuttle body flap was to protect the SME's and for pitch control during aerodynamic reentry.

[Prober]

Excellent moves in the right direction...

http://www.nasaspaceflight.com/2012/02/aerojets-confidence-next-generation-engine-green-propellants/

great writeup.

[Rocket Science]

Nice comprehensive article Chris G and thanks again to Lee Jay! The excitement continues to build…

[sdsds]

I really like the focus the article puts on the launch vehicle configuration. It's an Atlas 4xx because it flies with the Centaur exposed rather than enclosed; it has no fairing. This recent buffet testing should lay to rest most concerns about that, the weirdness of the "Z511" image (http://www.nasaspaceflight.com/wp-content/uploads/2012/06/Z511.jpg)  notwithstanding. The article also makes the point that during an abort with zero solids the range wouldn't need to destroy the vehicle while the crew were still getting away.

I'm a bit confused though about emergency egress. I get the bit shown in the photo where a gangplank from the existing mobile launch platform gets the crew into the vehicle. But what if they need to get down in a hurry? (I'm hoping the answer involves a zip-line!

[Alpha Control]

Fine article, Chris G! My optimism remains cautious, but I am hopeful that the "baby orbiter" will indeed have her day in the sun, and that we will once again see a spaceplane descend from space and land on a runway.

[Alpha Control]

I really like the focus the article puts on the launch vehicle configuration. It's an Atlas 4xx because it flies with the Centaur exposed rather than enclosed; it has no fairing. This recent buffet testing should lay to rest most concerns about that, the weirdness of the "Z511" image (http://www.nasaspaceflight.com/wp-content/uploads/2012/06/Z511.jpg)  notwithstanding. The article also makes the point that during an abort with zero solids the range wouldn't need to destroy the vehicle while the crew were still getting away.

I'm a bit confused though about emergency egress. I get the bit shown in the photo where a gangplank from the existing mobile launch platform gets the crew into the vehicle. But what if they need to get down in a hurry? (I'm hoping the answer involves a zip-line!

Sdsds, I'm not clear on your reference to the "exposed Centaur". Are you referring to the fact that a fairing would provide a uniform airflow for the Centaur behind it, whereas the Dream Chaser will not?
Thanks,
David

[Downix]

I really like the focus the article puts on the launch vehicle configuration. It's an Atlas 4xx because it flies with the Centaur exposed rather than enclosed; it has no fairing. This recent buffet testing should lay to rest most concerns about that, the weirdness of the "Z511" image (http://www.nasaspaceflight.com/wp-content/uploads/2012/06/Z511.jpg)  notwithstanding. The article also makes the point that during an abort with zero solids the range wouldn't need to destroy the vehicle while the crew were still getting away.

I'm a bit confused though about emergency egress. I get the bit shown in the photo where a gangplank from the existing mobile launch platform gets the crew into the vehicle. But what if they need to get down in a hurry? (I'm hoping the answer involves a zip-line!

Sdsds, I'm not clear on your reference to the "exposed Centaur". Are you referring to the fact that a fairing would provide a uniform airflow for the Centaur behind it, whereas the Dream Chaser will not?
Thanks,
David

No, it literally means as it says, the Centaur is exposed.  The 5xx series Atlas' have the Centaur enshrouded.

[Lars_J]

Alpha Control,
Atlas V 4XX on the left, 5XX on the right. The 5XX flights have both the Centaur and payload inside the fairing.

[Alpha Control]

Thanks Lars and Downix. Appreciate the clarification. I didn't realize that the entire Centaur was enclosed within the fairing for the 5 series.

[BrightLight]

This site is wonderful,
where else can we get such deep and accurate reporting about such exciting developments. Being a fan of lifting bodies and the HL-20/DC is specific - there is no other place to see the development of this long awaited space plane.
Thanks Chris!!

[manboy]

Do we know what kind of TPS it will use (TUFROC?)?

[Prober]

When was the last time the Centaur was launched exposed?

Would be good to look up.

[Jim]

When was the last time the Centaur was launched exposed?

Would be good to look up.

3 days ago. 

Shakes head.

[Prober]

When was the last time the Centaur was launched exposed?

Would be good to look up.

3 days ago. 

Shakes head.

Not close to the fine details like you folk.

[ChrisGebhardt]

Moreover, the vehicle’s docking adapter will be removed and replaced after each mission instead of being reused.

According to Mark Sirangelo, “The economics work out that it’s not really advantageous to reuse it.”  This goes toward an explanation for why there is no body flap on the back of Dream Chaser, like there was on Shuttle, to protect Dream Chaser’s docking adaptor.

I thought the purpose of the Shuttle body flap was to protect the SME's and for pitch control during aerodynamic reentry.

Yes, it was (for Shuttle). As the article says, Shuttle had the body for protection. Since there's nothing worth protecting on Dream Chaser's aft (i.e., the docking adapter), there will be no body flap.

[clongton]

My personally preferred commercial crew stack - Atlas-V/DC.
Thank you Chris(s). Nicely done!

[ChrisGebhardt]

Thanks. Good article.

I have one question about this paragraph:

Even more impressive is the seeming lack of modifications needed to the Atlas V’s ground equipment currently in use by United Launch Alliance. In fact, Sierra Nevada indicates that only an adaptor to the current launch tower would be needed for vehicle access – both for the crews of Dream Chaser and support personnel who would assist astronauts with entry into the vehicle and final preparations for launch.

Wouldn't you need a pad with crew ingress/egress as explained by Gass on page 8 of the ULA presentation at the Augustine Committee?   

Human rating impacts to flight-proven existing EELV
are understood
– Separate VIF/MLP or pad with crew ingress/egress

http://www.nasa.gov/pdf/361835main_08%20-%20ULA%20%201.0_Augustine_Public_6_17_09_final_R1.pdf

See also p. 5 of this ULA document:
http://www.ulalaunch.com/site/docs/publications/AtlasDeltaCrewLaunch2010.pdf

OK. Let's actually look at what those documents say.

The Augustine Committee made a blanket, without in-depth analysis assumption that ULA would need a completely new VIF and ML for the Atlas V 402 manned launch vehicle.

This assumption is now proven incorrect by ULA based on the Dream Chaser's narrowing design and capabilities. Thus, a new VIF and MLP are unnecessary.

For the ULA doc, it quite literally says, "launch site modifications to accommodate crew ingress and emergency egress" (pg. 5).

It says nothing about a VIF of MLP being needed, only that a modification to provide crew access and egress is necessary.

Let us also remember here that egress does not necessarily mean "There's an emergency. Everyone out!" It means, "we scrubbed for the day because of xxxxxx."

I'm a bit confused though about emergency egress. I get the bit shown in the photo where a gangplank from the existing mobile launch platform gets the crew into the vehicle. But what if they need to get down in a hurry? (I'm hoping the answer involves a zip-line!

For a launch pad abort, SNC is looking at a separation of Dream Chaser from the Atlas V 402 stack and subsequent landing on a nearby runway, thereby eliminating the need for an emergency egress system for the crew at the pad. How that Pad Abort going to happen? I'm not sure. But that's what Mark Sirangelo noted in his interview with Lee Jay.

[Danderman]

I really like the focus the article puts on the launch vehicle configuration. It's an Atlas 4xx because it flies with the Centaur exposed rather than enclosed; it has no fairing.

Atlas 4xx has a limit of about 20,000 lbs for payload. Does the DreamChaser really have such a low weight?

[Rocket Science]

This was how a pad abort was simulated for the HL-20:

http://www.coe.pku.edu.cn/tpic/2011721145939517.pdf

[dbooker]

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.  Plus the docking adapter is only one time use?  While I'm really rooting Dream Chaser I wonder if it is really a sustainable model.  Yeah, it will cost less than a shuttle to launch but less than a Dragon? 

And it doesn't seem like it will have early abort capability.  What if the there is a fault that causes an Atlas engine shutdown 10 seconds after launch.  Will those hybrid rockets on the Dream Chaser really have the thrust to safely allow the vehicle to get away?  And what happens when that thrust hits the oxygen and hydrogen in the Centaur?

[Lee Jay]

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).

And it doesn't seem like it will have early abort capability.

They told me it has anytime abort capability.

[Zero-G]

I'm a bit confused though about emergency egress. I get the bit shown in the photo where a gangplank from the existing mobile launch platform gets the crew into the vehicle. But what if they need to get down in a hurry? (I'm hoping the answer involves a zip-line!

For a launch pad abort, SNC is looking at a separation of Dream Chaser from the Atlas V 402 stack and subsequent landing on a nearby runway, thereby eliminating the need for an emergency egress system for the crew at the pad. How that Pad Abort going to happen? I'm not sure. But that's what Mark Sirangelo noted in his interview with Lee Jay.

What would the pad crew, who is assisting the astronauts, do, if they need to get away from the pad and the rocket in a hurry? (Or the astronauts, when they are not settled in yet.)

[vt_hokie]

I envy the folks who are making this stuff happen - I'd love to work on a project like this one!

[Dappa]

I really like the focus the article puts on the launch vehicle configuration. It's an Atlas 4xx because it flies with the Centaur exposed rather than enclosed; it has no fairing.

Wouldn't dropping the fairing make it an x02 instead of a 4xx? There's no 4m fairing (x), no solids (0), and a dual engine Centaur(2).

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.

[laszlo]

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.  Plus the docking adapter is only one time use?...

The tiles are mounted on a modular carrier. Replacing them is more like changing the cowling on an aircraft (minutes) than retiling your shower (days).

The entire booster is only used one time, why worry about the docking adapter? Consider it part of the booster. Seriously, if it's cheaper to make a new one than to refurbish the old, what's the problem?

Cheers,

Laszlo

[Jim]

The entire booster is only used one time, why worry about the docking adapter? Consider it part of the booster. Seriously, if it's cheaper to make a new one than to refurbish the old, what's the problem?

Because it is not part of the booster.  It is a integral part of the spacecraft and its pressure vessel.

[Rocket Science]

I'm a bit confused though about emergency egress. I get the bit shown in the photo where a gangplank from the existing mobile launch platform gets the crew into the vehicle. But what if they need to get down in a hurry? (I'm hoping the answer involves a zip-line!

For a launch pad abort, SNC is looking at a separation of Dream Chaser from the Atlas V 402 stack and subsequent landing on a nearby runway, thereby eliminating the need for an emergency egress system for the crew at the pad. How that Pad Abort going to happen? I'm not sure. But that's what Mark Sirangelo noted in his interview with Lee Jay.

What would the pad crew, who is assisting the astronauts, do, if they need to get away from the pad and the rocket in a hurry? (Or the astronauts, when they are not settled in yet.)

Pad safety is an important issue for both the close-out crew and flight crew. I would believe that would be part of the agreement with SNC and the launch services provider ULA. There are multiple possible scenarios possible that could happen that would require immediate evacuation (a partial crew ingress situation or just about complete etc…). The worst case of course would be would be crew a full-up pad abort and landing at the SLF or the “Skid Strip” runway. The hard lessons learned from Apollo 1 I’m sure has not been forgotten.  Perhaps Jim can illuminate changes to the pad on ULA’s side in preparation for services, being more than common to both Dream Chaser's or CST-100’s needs.

[laszlo]

The entire booster is only used one time, why worry about the docking adapter? Consider it part of the booster. Seriously, if it's cheaper to make a new one than to refurbish the old, what's the problem?

Because it is not part of the booster.  It is a integral part of the spacecraft and its pressure vessel.

So much for using humorous rhetorical questions to make a point.

It's still not a problem. It's the 21st Century and we have bolt & gasket technology. Don't confuse integral with permanent.

[Jim]

So much for using humorous rhetorical questions to make a point.

It's still not a problem. It's the 21st Century and we have bolt & gasket technology. Don't confuse integral with permanent.

Your point and humor failed because it is wrong. Don't confuse technology as a fix for proper engineering.

[Lee Jay]

So much for using humorous rhetorical questions to make a point.

It's still not a problem. It's the 21st Century and we have bolt & gasket technology. Don't confuse integral with permanent.

Your point and humor failed because it is wrong. Don't confuse technology as a fix for proper engineering.

Doesn't SpaceX jettison Dragon's docking adapter before entry?

[mr. mark]

So much for using humorous rhetorical questions to make a point.

It's still not a problem. It's the 21st Century and we have bolt & gasket technology. Don't confuse integral with permanent.

Your point and humor failed because it is wrong. Don't confuse technology as a fix for proper engineering.

Doesn't SpaceX jettison Dragon's docking adapter before entry?

I don't think so, have to look into that. From what I'm hearing, a two month turnaround at best for Dreamchaser. So what is being advertised to the public as a quick turnaround vehicle is just not so.

[Lee Jay]

From what I'm hearing, a two month turnaround at best for Dreamchaser. So what is being advertised to the public as a quick turnaround vehicle is just not so.

Typical orbiter turnarounds were three times as long.

[Rocket Science]

They will build multiple vehicles so that will factor into the plus side how many launches take place over a year…

[mike robel]

I really like this vehicle.  But I worry a little about the Clean Room graphic at the end of the article.  It reminds me of the early shuttle processing concepts.

Still, a great article!  Thanks Chris and NSF.

[Danderman]

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.

[laszlo]

So much for using humorous rhetorical questions to make a point.

It's still not a problem. It's the 21st Century and we have bolt & gasket technology. Don't confuse integral with permanent.

Your point and humor failed because it is wrong. Don't confuse technology as a fix for proper engineering.

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?

For that matter, how is replacing the docking adapter after the flight different from swapping out any other component?

The actual question was about the desirability of refurbishing vs. replacing. Sierra Nevada has decided that it's more cost-effective to replace. Since it's their spacecraft and design, they ought to know.

[Jim]

For that matter, how is replacing the docking adapter after the flight different from swapping out any other component?

Other components do not deal with the pressure vessel.

[Jim]

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.

[BrightLight]

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.

[A_M_Swallow]

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

[Lee Jay]

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

Every Soyuz and Progress launch?

[BrightLight]

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.

[BrightLight]

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?

[pathfinder_01]

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.

[clongton]

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?

[BrightLight]

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?

[Lee Jay]

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.

[erioladastra]

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.

[Orbital Debris]

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. 

[Orbital Debris]

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.

[lesxiarxis]

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

[erioladastra]

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.

[Robotbeat]

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.

[Ronsmytheiii]

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:

[Robotbeat]

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.

[Ronsmytheiii]

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.

[Go4TLI]

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

[Robotbeat]

Thanks, both of you

[Rocket Science]

Neat Schlieren photography image of Dream Chaser on the stack in the Marshall wind tunnel...

http://www.nasa.gov/centers/marshall/about/star/star120516.html

[Jason1701]

Great header for Chris's next DC article!

[Rocket Science]

Great header for Chris's next DC article!

I might make it my desktop...

[BrightLight]

Mach 5, just another 12 or so to go

[Rocket Science]

Mach 5, just another 12 or so to go

Looks good going uphill...

[Lurker Steve]

Neat Schlieren photography image of Dream Chaser on the stack in the Marshall wind tunnel...

http://www.nasa.gov/centers/marshall/about/star/star120516.html

I thought the tail fins would make a larger wake in the airflow, but it appears that blends into the wake caused by the inter-stage adapter / top of the centaur fairly well.

I see another wake caused by the transition from the centaur to the first stage, and then another wake caused by a protusion at the bottom of the first stage. Is that a problem with the CCB model, or are they looking at airflow with an SRB attached in a Atlas 412 configuration ?

[nacnud]

I think that is a prop line.

[Robotbeat]

Neat Schlieren photography image of Dream Chaser on the stack in the Marshall wind tunnel...

http://www.nasa.gov/centers/marshall/about/star/star120516.html

I love the Schlieren... I've done it several times, and it always looks so cool!

[Lars_J]

Neat Schlieren photography image of Dream Chaser on the stack in the Marshall wind tunnel...

http://www.nasa.gov/centers/marshall/about/star/star120516.html

I thought the tail fins would make a larger wake in the airflow, but it appears that blends into the wake caused by the inter-stage adapter / top of the centaur fairly well.

I see another wake caused by the transition from the centaur to the first stage, and then another wake caused by a protusion at the bottom of the first stage. Is that a problem with the CCB model, or are they looking at airflow with an SRB attached in a Atlas 412 configuration ?

I think that is a prop line.

Yep - see attached image.

[Rocket Science]

Neat Schlieren photography image of Dream Chaser on the stack in the Marshall wind tunnel...

http://www.nasa.gov/centers/marshall/about/star/star120516.html

I love the Schlieren... I've done it several times, and it always looks so cool!

A picture is worth a thousand....

[vt_hokie]

It makes me hopeful to see that real engineering is going on with this program on several fronts, and it's potentially a lot more than just a cool concept!

[sdsds]

Neat Schlieren photography image of Dream Chaser on the stack in the Marshall wind tunnel...

This is really cool! Questions, though:

The text mentions, "configurations were tested [...] at various launch vehicle roll angles." What about pitch? Does this particular image look like "zero angle of attack"? Has SNC or ULA said anything about pitch angles on the trajectory they intend to fly? Or about wind-shear launch constraints?

[vulture4]

Does anyone know the anticipated gross weight, lift-to-drag ratio, and airspeed at touchdown? Crosswind tolerance? CG range? It would be interesting to compare the DC with the X-37 given their different configuratoins, though of course data on the latter is not very accessible.

[BrightLight]

Does anyone know the anticipated gross weight, lift-to-drag ratio, and airspeed at touchdown? Crosswind tolerance? CG range? It would be interesting to compare the DC with the X-37 given their different configuratoins, though of course data on the latter is not very accessible.

There are a number of papers available on the HL-20, a close second to DC

http://www.ninfinger.org/models/vault2008/HL-20/HL-20%20MODEL.pdf

Google HL-20

[manboy]

So much for using humorous rhetorical questions to make a point.

It's still not a problem. It's the 21st Century and we have bolt & gasket technology. Don't confuse integral with permanent.

Your point and humor failed because it is wrong. Don't confuse technology as a fix for proper engineering.

Doesn't SpaceX jettison Dragon's docking adapter before entry?

Berthing mechanism. And no.