Sierra Space Dream Chaser DISCUSSION Thread (was SNC)

[vt_hokie]

I think it's questionable whether or not crew Dream Chaser would have had a smoother development path than Starliner.  What I do believe is that it would have been a better long term investment with more potential beyond the initial commercial crew missions, and that Starliner has a much higher probability of being a dead end.

[mandrewa]

Here's a comparison of the different options for carrying cargo to orbit. Like several other people in this thread I searched for Dream Chaser's payload volume and was unable to find it.

This list is restricted to the democracies.  I believe this is all of the space cargo vessels that either exist or are actually being built.


Cargo Dragon V2
---------------
6.4 mt dry mass
6.0 mt up mass
2.5 mt down mass
 9.3 m^3 pressurized volume
12.1 m^3 unpressurized volume (standard trunk)
37.0 m^3 unpressurized volume (extended trunk)
maximum 10 day free flight
maximum 9 month docked to supporting station
reused


Cygnus, enhanced version
------------------------
3.4 mt dry mass
3.8 mt up mass (footnote 1)
27.0 m^3 pressurized volume
27.0 m^3 disposal volume
expended


Cargo Dream Chaser
------------------
NET 2023
(Dream Chaser lander + Shooting Stars module)
5.0 mt pressurized up mass
0.5 mt unpressurized up mass
1.75 mt pressurized down mass (with maximum 1.5 G force rentry)
3.25 mt disposal mass
lander is reused, module is expended


Cargo Starship
--------------
NET 2024
~ 120 mt dry mass
~ 150 mt pressurized up mass
reused


HTV-X
-----------
NET 2024
8.3 mt dry mass
4.07 mt pressurized up mass
1.75 mt unpressurized up mass
78 m^3 pressurized volume
maximum 6 months docked to supporting station
maximum 1.5 years free flight
expended

Footnote 1: The Cygnus up mass limit will depend on the rocket launching it.  3.8 mt is the largest payload mass launched so far.  But Northrup-Grumman claims 3.5 metric tons is the limit. That may be based on the Antares rocket.

[JAFO]

blah blah blah...

You seem to think that the ability to copy and post things you find on the internet makes you a valued member and "authoritative expert" on this forum, but the truth is far from that. I have no interest in debating you but to update people new to her, Dream Chaser actually traces her heritage back to the Soviet BOR-4 program and even the NASA light/heavyweight lifting bodies.

(One could also make a good argument that the Boeing Starliner traces its heritage all the way back to Max Faget’s first capsule and it has just been building on 1950s era research and development. Starliner has often been called Apollo on steroids, giving even less excuse for Boeing's repeated delays.)

[Lee Jay]

My point is that Dream Chaser without the fairing represents an aerodynamic challenge for the launch vehicle. This would take time and money to solve. It appears to have been enough of a problem to make the weight and expense of the folding wing mechanism and the weight and expense of the fairing worth it for the cargo version, which does not need an abort system.

If you have any evidence that that is the reason, I'd like to see it.  I was told the exact opposite directly by them - that the fairing is a far larger aerodynamic problem for the LV than DC would be in free-stream.

[JEF_300]

DreamChaser has struggled just as much as Starliner and the bar for unscrewed flight is much lower than for a manned capsule.  There’s zero reason to think they’d be done by now any more than Boeing (although at least they would have been a lot cheaper).

A: Dreamchaser has developed about as fast as Starliner has, despite:
    - Boeing having more internal capital and resources than Sierra Nevada/Space
    - A spaceplane being a more difficult engineering challenge than a capsule
B: NASA awarded Boeing more money than they did Sierra Nevada
C: NASA awarded significant funding to Boeing years before doing so with Sierra Nevada

All things considered, I think there's lots of reasons to think they'd be more done by now than Boeing is.

I must be reading this wrong. In A you say Boeing has more money and a spaceplane is more difficult, B that NASA gave more money to Boeing, and C NASA gave more more money to Boeing years before SNC.

But your conclusion is that SNC should be further along? Don't you mean Boeing should be further along?

I guess you were reading it wrong. My conclusion is that SNC would be further along had they had the support Boeing has.

[JAFO]

DreamChaser has struggled just as much as Starliner and the bar for unscrewed flight is much lower than for a manned capsule.  There’s zero reason to think they’d be done by now any more than Boeing (although at least they would have been a lot cheaper).

A: Dreamchaser has developed about as fast as Starliner has, despite:
    - Boeing having more internal capital and resources than Sierra Nevada/Space
    - A spaceplane being a more difficult engineering challenge than a capsule
B: NASA awarded Boeing more money than they did Sierra Nevada
C: NASA awarded significant funding to Boeing years before doing so with Sierra Nevada

All things considered, I think there's lots of reasons to think they'd be more done by now than Boeing is.

I must be reading this wrong. In A you say Boeing has more money and a spaceplane is more difficult, B that NASA gave more money to Boeing, and C NASA gave more more money to Boeing years before SNC.

But your conclusion is that SNC should be further along? Don't you mean Boeing should be further along?

I guess you were reading it wrong. My conclusion is that SNC would be further along had they had the support Boeing has.

My apologies, and I agree.

[JEF_300]

My point is that Dream Chaser without the fairing represents an aerodynamic challenge for the launch vehicle. This would take time and money to solve. It appears to have been enough of a problem to make the weight and expense of the folding wing mechanism and the weight and expense of the fairing worth it for the cargo version, which does not need an abort system.

If you have any evidence that that is the reason, I'd like to see it.  I was told the exact opposite directly by them - that the fairing is a far larger aerodynamic problem for the LV than DC would be in free-stream.

Which makes sense if you think about it. Sure, a Dreamchaser in the open will cause some lift-forces on weird vectors, but that's not going to be anything that a tiny bit of gimballing from the main engines won't totally counteract. The fairing, meanwhile, massively increases the forward area of the vehicle, and thus increases the aerodynamic losses experienced on ascent (assuming we're talking about Atlas).

We've got to remember that these are real rockets being flown by computers, not rockets in KSP being flown by hand. If modern guidance software can manage the Astra slide, then I don't see any reason to believe it couldn't handle Dreamchaser.

[Jim]

My point is that Dream Chaser without the fairing represents an aerodynamic challenge for the launch vehicle. This would take time and money to solve. It appears to have been enough of a problem to make the weight and expense of the folding wing mechanism and the weight and expense of the fairing worth it for the cargo version, which does not need an abort system.

If you have any evidence that that is the reason, I'd like to see it.  I was told the exact opposite directly by them - that the fairing is a far larger aerodynamic problem for the LV than DC would be in free-stream.

Wrong.   Unsymmetrical load would be more of a problem.   Vulcan isn't a hammerhead like the Atlas V 5XX.  Vulcan has a similar fairing/adapter system like Delta IV.  Removing fairing now puts aeroloads directly on the adapter cone and the spacecraft  asymmetrical loads.

[mandrewa]

My point is that Dream Chaser without the fairing represents an aerodynamic challenge for the launch vehicle. This would take time and money to solve. It appears to have been enough of a problem to make the weight and expense of the folding wing mechanism and the weight and expense of the fairing worth it for the cargo version, which does not need an abort system.

If you have any evidence that that is the reason, I'd like to see it.  I was told the exact opposite directly by them - that the fairing is a far larger aerodynamic problem for the LV than DC would be in free-stream.

If the fairing is a larger aerodynamic problem, why in the world are they launching it in a fairing?

[JEF_300]

If the fairing is a larger aerodynamic problem, why in the world are they launching it in a fairing?

Because extending solar panels don't do well at a high airspeed perhaps?

[mandrewa]

If the fairing is a larger aerodynamic problem, why in the world are they launching it in a fairing?

Because extending solar panels don't do well at a high airspeed perhaps?

That's a good answer.  And of course they need the Shooting Star to bring the payload mass and volume up to reasonable numbers.

But that raises another possibility.  The volume of the DC-201, or Crew Dream Chaser, is 40% larger than the current Cargo Dream Chaser. Or at least I assume Sierra Space was talking about volume when they said the DC-201 was 40% larger.  I wonder if they did a cargo version of the DC-201 if they might not end up with a vehicle that has a larger payload volume than the current Dream Chaser plus Shooting Star combination.

And in that case, this might eliminate the need for Shooting Star, and it would also mean there was more commonality between the this future Cargo Dream Chaser and the future Crew Dream Chaser.

[Lee Jay]

My point is that Dream Chaser without the fairing represents an aerodynamic challenge for the launch vehicle. This would take time and money to solve. It appears to have been enough of a problem to make the weight and expense of the folding wing mechanism and the weight and expense of the fairing worth it for the cargo version, which does not need an abort system.

If you have any evidence that that is the reason, I'd like to see it.  I was told the exact opposite directly by them - that the fairing is a far larger aerodynamic problem for the LV than DC would be in free-stream.

Wrong.   Unsymmetrical load would be more of a problem.   Vulcan isn't a hammerhead like the Atlas V 5XX.  Vulcan has a similar fairing/adapter system like Delta IV.  Removing fairing now puts aeroloads directly on the adapter cone and the spacecraft  asymmetrical loads.

Well, Steve Lindsey told me that in person.  He said the aero loads from the fairing were massively higher than from an exposed vehicle.

[Steven Pietrobon]

..., Dream Chaser actually traces her heritage back to the Soviet BOR-4 program and even the NASA light/heavyweight lifting bodies.

It actually goes back to the USAF PRIME re-entry test vehicle from 1966!

https://space.skyrocket.de/doc_sdat/prime.htm

[Alpha Control]

..., Dream Chaser actually traces her heritage back to the Soviet BOR-4 program and even the NASA light/heavyweight lifting bodies.

It actually goes back to the USAF PRIME re-entry test vehicle from 1966!

https://space.skyrocket.de/doc_sdat/prime.htm

Thanks for posting that, Steven. I wasn't aware of the X-23 program. Did this feed into the Space Shuttle design at all?

[Steven Pietrobon]

Thanks for posting that, Steven. I wasn't aware of the X-23 program. Did this feed into the Space Shuttle design at all?

I don't know, but I would have not been surprised if NASA used the data from PRIME (and the previous ASSET) flights to help model Space Shuttle re-entry.

https://space.skyrocket.de/doc_sdat/asset-aev.htm

[shintoo]

From the Spacenews article (https://spacenews.com/sierra-space-describes-long-term-plans-for-dream-chaser-and-inflatable-modules/):

Vice hinted that the company has longer-term plans for Dream Chaser that could possibly allow it to end dependence on other companies’ launch vehicles. “We’re thinking about investigating the right technologies in thermal and propulsion and materials that allows us to potentially think about the staging options that would allow us, for the first time, have horizontal takeoff,” he said. He didn’t offer a schedule for developing that version of Dream Chaser.

(Emphasis mine.)

This is so very far out into the future, considering we haven't seen even the first launch yet, but it is interesting to consider what they could be referring to here. Dropping from a mothership plane (Roc, Cosmic Girl-esque) perhaps? A 747 like Cosmic Girl would definitely not have the capacity to airlaunch something like Dream Chaser, and I doubt the Roc could either, with a booster sizeable enough to get a massive DC to orbit. So they must be thinking about something entirely new.

Far, far off into the future for sure.

[adrianwyard]

In the article Tom Vice says "We just think [Dream Chaser] is the way people are going to want to fly back and land.” By context this appears to be referring to the next version and he did not say *launch* and land. If that was intentional I wonder if this means there will still not be an abort capability.

[butters]

A 330 cubic meter inflatable module. Deja vu!

In fairness, Sierra has a significant advantage over the prior efforts by Bigelow purely because of launch vehicle options. They're not limited to Atlas V 551, which presented a prohibitive challenge with electrical power for a module of that size. They can go heavier with Vulcan, or New Glenn if they need more fairing volume for packaging the solar arrays.

[JEF_300]

From the Spacenews article (https://spacenews.com/sierra-space-describes-long-term-plans-for-dream-chaser-and-inflatable-modules/):

Vice hinted that the company has longer-term plans for Dream Chaser that could possibly allow it to end dependence on other companies’ launch vehicles. “We’re thinking about investigating the right technologies in thermal and propulsion and materials that allows us to potentially think about the staging options that would allow us, for the first time, have horizontal takeoff,” he said. He didn’t offer a schedule for developing that version of Dream Chaser.

(Emphasis mine.)

This is so very far out into the future, considering we haven't seen even the first launch yet, but it is interesting to consider what they could be referring to here. Dropping from a mothership plane (Roc, Cosmic Girl-esque) perhaps? A 747 like Cosmic Girl would definitely not have the capacity to airlaunch something like Dream Chaser, and I doubt the Roc could either, with a booster sizeable enough to get a massive DC to orbit. So they must be thinking about something entirely new.

Far, far off into the future for sure.

Well, I'm not so sure. In the past there have been quite a lot of, admittedly rather out of date, renders of a Dreamchaser being launched off Roc. At the very least they at one point thought it was possible.

Here's a NASASpaceflight article about Dreamchaser on Roc from 2014:
https://www.nasaspaceflight.com/2014/10/dream-chaser-eyes-rides-with-under-review-stratolaunch-system/
Image bellow is the render from that time:


I suspect that if you go with an all hydrolox launcher design, it might just barely be possible to build rocket that can launch Dreamchaser from Roc. It would certainly explain Stratolaunch's design decisions back when they were working on the PGA engine; it was a fuel-rich staged combustion hydrolox booster engine, about the size of Merlin 1D. Perfect for making your launch vehicle as light, when fueled, as can be managed. Please note that this is all purely vibes/it's-what-make-sense-to-me based. I haven't actually sat down and done the math for it.

[whitelancer64]

From the Spacenews article (https://spacenews.com/sierra-space-describes-long-term-plans-for-dream-chaser-and-inflatable-modules/):

Vice hinted that the company has longer-term plans for Dream Chaser that could possibly allow it to end dependence on other companies’ launch vehicles. “We’re thinking about investigating the right technologies in thermal and propulsion and materials that allows us to potentially think about the staging options that would allow us, for the first time, have horizontal takeoff,” he said. He didn’t offer a schedule for developing that version of Dream Chaser.

(Emphasis mine.)

This is so very far out into the future, considering we haven't seen even the first launch yet, but it is interesting to consider what they could be referring to here. Dropping from a mothership plane (Roc, Cosmic Girl-esque) perhaps? A 747 like Cosmic Girl would definitely not have the capacity to airlaunch something like Dream Chaser, and I doubt the Roc could either, with a booster sizeable enough to get a massive DC to orbit. So they must be thinking about something entirely new.

Far, far off into the future for sure.

Well, I'm not so sure. In the past there have been quite a lot of, admittedly rather out of date, renders of a Dreamchaser being launched off Roc. At the very least they at one point thought it was possible.

Here's a NASASpaceflight article about Dreamchaser on Roc from 2014:
https://www.nasaspaceflight.com/2014/10/dream-chaser-eyes-rides-with-under-review-stratolaunch-system/
Image bellow is the render from that time:


I suspect that if you go with an all hydrolox launcher design, it might just barely be possible to build rocket that can launch Dreamchaser from Roc. It would certainly explain Stratolaunch's design decisions back when they were working on the PGA engine; it was a fuel-rich staged combustion hydrolox booster engine, about the size of Merlin 1D. Perfect for making your launch vehicle as light, when fueled, as can be managed. Please note that this is all purely vibes/it's-what-make-sense-to-me based. I haven't actually sat down and done the math for it.

Note the rocket shown was called the Pegasus II, in development by Orbital (prior to their merger with ATK) in partnership with Stratolaunch. It was a 3 stage rocket, the first two stages were solid rocket motors, and the third stage was hydrolox, powered by one or two RL-10 engines. It had a payload capacity of 13,500 lb (6.1 metric tons) to LEO.

The DreamChaser to be launched was a 75% scale variant designed to be capable of flying 3 passengers or cargo.

Additional info: the Pegasus II solid rocket motors were the same diameter as the Shuttle SRB but had a carbon composite casing and a more energetic propellant mix. The first stage (which had two short wings and a V tail) was intended to be recoveable after splashdown.

The design was modified in late 2014 to use all solid rocket motors. However, the economic / business case for it never closed, so development was shelved, and later abandoned altogether.