Sierra Space Dream Chaser DISCUSSION Thread (was SNC)

[adrianwyard]

For the current Dream Chaser design I suspect it comes down to trade studies showing the benefits of adding forward cockpit style windows do not outweigh the costs. The costs being mainly weight, maintenance (an issue for Shuttle) but perhaps also structural margins if there are lots of them. To nix windows such a study would need to place great confidence in synthetic vision and/or automated landing, which would have been controversial a decade ago but not so much now.

For QueSST (and probably the DC-201 as pictured) forward windows would not allow you to see over the nose when landing, so that's a fine reason to delete them.

[JAFO]

Somewhat off-topic (since this obviously wouldn't apply to Dream Chaser in any case, but would've been relevant to other Commercial Crew entrants like Dragon and Starliner that use more traditional capsules): if I'm reading this correctly, would this preclude an Orion- or Soyuz-style "tractor" abort motor tower that covers the windows with a fairing during early launch phases? A natural reading of "available through all flight phases" would suggest as such, but perhaps there is other context that excludes launch phases from this definition.

I am not sure but the requirement is the following:

The spacecraft shall provide windows that are available for use by the crew through all phases of flight that provide direct, non-electronic, through-the-hull viewing and the unobstructed fields of-view necessary to perform crew viewing tasks. [R.CTS.177]

The rest of the text is the rationale for the requirement. I am not sure if the ascent would require an unobstructed view in order to perform a crew viewing task. It's not clear to me what is a crew viewing task and if there is such a task on ascent.

The QueSST doesn't have forward cockpit windows either.

The Shuttle engineers in the 1970s figured out how to do to forward facing windows. I don't understand why this suddenly seems to be so difficult, and that overhead windows are the only way to have windows?? Am I missing something? Thanks.

Wonder if it's the same people who said there was no longer a need for a gun in a fighter because missiles were so reliable?

With that said, I've shot enough Cat III autoland approaches to know that modern systems are reliable enough that I don't really need to see outside to land if everything is working right. But it's still freaky, and I don't think I'd ever feel comfortable doing one with my hands in my lap. Just too many ways for things to go wrong.


 

[Lee Jay]

For the current Dream Chaser design I suspect it comes down to trade studies showing the benefits of adding forward cockpit style windows do not outweigh the costs. The costs being mainly weight, maintenance (an issue for Shuttle) but perhaps also structural margins if there are lots of them. To nix windows such a study would need to place great confidence in synthetic vision and/or automated landing, which would have been controversial a decade ago but not so much now.

For QueSST (and probably the DC-201 as pictured) forward windows would not allow you to see over the nose when landing, so that's a fine reason to delete them.

IIRC, Steve Lindsey said forward windows cost on the order of 500 pounds of cargo mass.  Ouch.

[edzieba]

Somewhat off-topic (since this obviously wouldn't apply to Dream Chaser in any case, but would've been relevant to other Commercial Crew entrants like Dragon and Starliner that use more traditional capsules): if I'm reading this correctly, would this preclude an Orion- or Soyuz-style "tractor" abort motor tower that covers the windows with a fairing during early launch phases? A natural reading of "available through all flight phases" would suggest as such, but perhaps there is other context that excludes launch phases from this definition.

I am not sure but the requirement is the following:

The spacecraft shall provide windows that are available for use by the crew through all phases of flight that provide direct, non-electronic, through-the-hull viewing and the unobstructed fields of-view necessary to perform crew viewing tasks. [R.CTS.177]

The rest of the text is the rationale for the requirement. I am not sure if the ascent would require an unobstructed view in order to perform a crew viewing task. It's not clear to me what is a crew viewing task and if there is such a task on ascent.

The QueSST doesn't have forward cockpit windows either.

The Shuttle engineers in the 1970s figured out how to do to forward facing windows. I don't understand why this suddenly seems to be so difficult, and that overhead windows are the only way to have windows?? Am I missing something? Thanks.

The Orbiter windows mere multiple layers of different (and expensive, and heavy) glasses, along with desiccant and purge systems to allow those windows to be optically useful when going from STP to vacuum through entry and back again - because windows that spent their time fogged or with ice formed inside them are not much good as windows.
Windows as that don't face right into entry plasma flow and are not safety critical are reasonable to add. Windows that both receive a significant portion of entry heating and are a safety critical system are not so trivial. A camera + display system has the opportunity to be both lighter mass, cheaper, and have additional redundancy (multiple cameras and displays).

[TrevorMonty]

Somewhat off-topic (since this obviously wouldn't apply to Dream Chaser in any case, but would've been relevant to other Commercial Crew entrants like Dragon and Starliner that use more traditional capsules): if I'm reading this correctly, would this preclude an Orion- or Soyuz-style "tractor" abort motor tower that covers the windows with a fairing during early launch phases? A natural reading of "available through all flight phases" would suggest as such, but perhaps there is other context that excludes launch phases from this definition.

I am not sure but the requirement is the following:

The spacecraft shall provide windows that are available for use by the crew through all phases of flight that provide direct, non-electronic, through-the-hull viewing and the unobstructed fields of-view necessary to perform crew viewing tasks. [R.CTS.177]

The rest of the text is the rationale for the requirement. I am not sure if the ascent would require an unobstructed view in order to perform a crew viewing task. It's not clear to me what is a crew viewing task and if there is such a task on ascent.

The QueSST doesn't have forward cockpit windows either.

The Shuttle engineers in the 1970s figured out how to do to forward facing windows. I don't understand why this suddenly seems to be so difficult, and that overhead windows are the only way to have windows?? Am I missing something? Thanks.

Wonder if it's the same people who said there was no longer a need for a gun in a fighter because missiles were so reliable?

With that said, I've shot enough Cat III autoland approaches to know that modern systems are reliable enough that I don't really need to see outside to land if everything is working right. But it's still freaky, and I don't think I'd ever feel comfortable doing one with my hands in my lap. Just too many ways for things to go wrong.

Flyby wire controls can also fail in which case window is only useful to see your end.

[niwax]

Somewhat off-topic (since this obviously wouldn't apply to Dream Chaser in any case, but would've been relevant to other Commercial Crew entrants like Dragon and Starliner that use more traditional capsules): if I'm reading this correctly, would this preclude an Orion- or Soyuz-style "tractor" abort motor tower that covers the windows with a fairing during early launch phases? A natural reading of "available through all flight phases" would suggest as such, but perhaps there is other context that excludes launch phases from this definition.

I am not sure but the requirement is the following:

The spacecraft shall provide windows that are available for use by the crew through all phases of flight that provide direct, non-electronic, through-the-hull viewing and the unobstructed fields of-view necessary to perform crew viewing tasks. [R.CTS.177]

The rest of the text is the rationale for the requirement. I am not sure if the ascent would require an unobstructed view in order to perform a crew viewing task. It's not clear to me what is a crew viewing task and if there is such a task on ascent.

The QueSST doesn't have forward cockpit windows either.

The Shuttle engineers in the 1970s figured out how to do to forward facing windows. I don't understand why this suddenly seems to be so difficult, and that overhead windows are the only way to have windows?? Am I missing something? Thanks.

Wonder if it's the same people who said there was no longer a need for a gun in a fighter because missiles were so reliable?

With that said, I've shot enough Cat III autoland approaches to know that modern systems are reliable enough that I don't really need to see outside to land if everything is working right. But it's still freaky, and I don't think I'd ever feel comfortable doing one with my hands in my lap. Just too many ways for things to go wrong.

Flyby wire controls can also fail in which case window is only useful to see your end.

If you have any kind of control failure you're going to be in trouble. It's the classic spaceplane fallacy, just because it looks like a plane and those land safely doesn't mean it applies to space. This thing comes down on a several thousand kilometer unpowered glide, actually reentering butt first, with no possibility of going around or holding while you run a checklist.

[tbellman]

Flyby wire controls can also fail in which case window is only useful to see your end.

But will DreamChaser actually be controllable by the crew during descent and landing?  Or will it be entirely autonomous?  In the latter case, it doesn't matter how well the crew can see outside through the windows; if the cameras/radar/whatever the computer uses fail, the crew can't do anything anyway.

[Lee Jay]

Flyby wire controls can also fail in which case window is only useful to see your end.

But will DreamChaser actually be controllable by the crew during descent and landing?  Or will it be entirely autonomous?  In the latter case, it doesn't matter how well the crew can see outside through the windows; if the cameras/radar/whatever the computer uses fail, the crew can't do anything anyway.

Both.

[JAFO]

Flyby wire controls can also fail in which case window is only useful to see your end.

If you have any kind of control failure you're going to be in trouble. It's the classic spaceplane fallacy, just because it looks like a plane and those land safely doesn't mean it applies to space. This thing comes down on a several thousand kilometer unpowered glide, actually reentering butt first, with no possibility of going around or holding while you run a checklist.

It reenters belly first, not butt first.

The FBW planes I've flown (13,000+ hours) have a stupid amount of control redundancy, and it all switches over invisibly in the event of a problem. DC does have fewer flight control surfaces than an airliner, it would be interesting to someday find out about their logic in nominal and off-nominal modes.

What keeps me up at night is a software problem. Me and my plane got into an argument the other day and I finally gave Hal a time out and did what I wanted to do manually, it was more of an "art of flying" vs "software logic of flying" debate, which I won.

Understandably, reentry software is far more complicated than climb/level off/descent/landing VNAV, so I'm sure SNC is burning electrons on that. Even something as "simple" as the RJ I used to fly had software problems many years after it was introduced into service. But the risks, rewards, and complexity of a FBW winged/whatever you want to call her vehicle are worth it vs the simplicity of a brutal capsule reentry.

The joke on my current ride is a new guy goes "What's it doing?", and the experienced pilot goes "Hang on, I've seen this shit before...."

[Lee Jay]

Flyby wire controls can also fail in which case window is only useful to see your end.

If you have any kind of control failure you're going to be in trouble. It's the classic spaceplane fallacy, just because it looks like a plane and those land safely doesn't mean it applies to space. This thing comes down on a several thousand kilometer unpowered glide, actually reentering butt first, with no possibility of going around or holding while you run a checklist.

The FBW planes I've flown (13,000+ hours) have a stupid amount of control redundancy, and it all switches over invisibly in the event of a problem. What keeps me up at night is a software problem, me and my plane got into an argument the other day and I finally gave Hal a time out and did what I wanted to do manually, it was more of an "art of flying" vs "software logic of flying" debate, which I won. Understandably, reentry software is far more complicated than climb and level of VNAV, so I'm sure SNC is burning electrons on that.

The joke on my plane is a new guy goes Whats it doing?, and the experienced pilot goes Wait, I've seen this shit before....

DC had triple redundancy in the flight controls last time I asked.

[Asteroza]

Flyby wire controls can also fail in which case window is only useful to see your end.

If you have any kind of control failure you're going to be in trouble. It's the classic spaceplane fallacy, just because it looks like a plane and those land safely doesn't mean it applies to space. This thing comes down on a several thousand kilometer unpowered glide, actually reentering butt first, with no possibility of going around or holding while you run a checklist.

The FBW planes I've flown (13,000+ hours) have a stupid amount of control redundancy, and it all switches over invisibly in the event of a problem. What keeps me up at night is a software problem, me and my plane got into an argument the other day and I finally gave Hal a time out and did what I wanted to do manually, it was more of an "art of flying" vs "software logic of flying" debate, which I won. Understandably, reentry software is far more complicated than climb and level of VNAV, so I'm sure SNC is burning electrons on that.

The joke on my plane is a new guy goes Whats it doing?, and the experienced pilot goes Wait, I've seen this shit before....

DC had triple redundancy in the flight controls last time I asked.

Isn't triple redundancy pretty standard for aerospace control-by-wire applications though?

[Robotbeat]

Somewhat off-topic (since this obviously wouldn't apply to Dream Chaser in any case, but would've been relevant to other Commercial Crew entrants like Dragon and Starliner that use more traditional capsules): if I'm reading this correctly, would this preclude an Orion- or Soyuz-style "tractor" abort motor tower that covers the windows with a fairing during early launch phases? A natural reading of "available through all flight phases" would suggest as such, but perhaps there is other context that excludes launch phases from this definition.

I am not sure but the requirement is the following:

The spacecraft shall provide windows that are available for use by the crew through all phases of flight that provide direct, non-electronic, through-the-hull viewing and the unobstructed fields of-view necessary to perform crew viewing tasks. [R.CTS.177]

The rest of the text is the rationale for the requirement. I am not sure if the ascent would require an unobstructed view in order to perform a crew viewing task. It's not clear to me what is a crew viewing task and if there is such a task on ascent.

The QueSST doesn't have forward cockpit windows either.

The Shuttle engineers in the 1970s figured out how to do to forward facing windows. I don't understand why this suddenly seems to be so difficult, and that overhead windows are the only way to have windows?? Am I missing something? Thanks.

Shuttle's windows were shielded mostly from the fiercest part of the flow, and they were completely flat. QUESST is very carefully shaped in an aerodynamic manner and would require a ridiculously long (and therefore heavy) window due to the very long nose, which is an essential part of its design.

[russianhalo117]

DutchSatellites
@DutchSatellites

As expected multiple sources have reported over the past several weeks that
@SierraSpaceCo
 Dream Chaser is no longer manifested on
@ulalaunch
 Vulcan flight #2. Primary reason is yet another set of delays in getting Dream Chaser ready for flight.
1:23 PM · Mar 5, 2023


https://twitter.com/DutchSatellites/status/1632492016465575941

If the second Vulcan launch won't be used to launch the first orbital Dream Chaser, the question is whether it will be repurposed for the launch of USSF-106.

No because NSSL launches require the launcher to be fully certified.

[Lampyridae]

Flyby wire controls can also fail in which case window is only useful to see your end.

If you have any kind of control failure you're going to be in trouble. It's the classic spaceplane fallacy, just because it looks like a plane and those land safely doesn't mean it applies to space. This thing comes down on a several thousand kilometer unpowered glide, actually reentering butt first, with no possibility of going around or holding while you run a checklist.

It reenters belly first, not butt first.

The FBW planes I've flown (13,000+ hours) have a stupid amount of control redundancy, and it all switches over invisibly in the event of a problem. DC does have fewer flight control surfaces than an airliner, it would be interesting to someday find out about their logic in nominal and off-nominal modes.

What keeps me up at night is a software problem. Me and my plane got into an argument the other day and I finally gave Hal a time out and did what I wanted to do manually, it was more of an "art of flying" vs "software logic of flying" debate, which I won.

Understandably, reentry software is far more complicated than climb/level off/descent/landing VNAV, so I'm sure SNC is burning electrons on that. Even something as "simple" as the RJ I used to fly had software problems many years after it was introduced into service. But the risks, rewards, and complexity of a FBW winged/whatever you want to call her vehicle are worth it vs the simplicity of a brutal capsule reentry.

The joke on my current ride is a new guy goes "What's it doing?", and the experienced pilot goes "Hang on, I've seen this shit before...."

I hear you on the "we don't need guns anymore" argument. Cameras have their own issues such as struggling with high contrast, resolving fast moving objects etc*. At least a periscope would give you a faithful representation of what's out there (as in, direct photons to retinas).

Digital to eyeballs spooks me because it always introduces the problem of software issues, or a bit getting flipped. Now your camera mode is stuck on ISO 80 and you're making a night landing approach that actually requires the human to see what's going.

*of course, this being NSF there's somebody who's personally worked on project XYZ to tell me I'm wrong