Sierra Nevada Thread (Dream Chaser, plus!)

[tater]

 

[Ol’ Musky Boi]

Conceptually the Dreamchaser spacecraft has been around for a while. It's design heritage goes all the way back to the soviet counterparts of the cancelled X-20 Dyna-soar... in the 1970s! However as far as spaceplanes go it's a practical design: it can land on conventional runways, fit in a fairing etc. I'm not sure how much it'll "revolutionise" space travel though, given that it's effectively just a reusable cargo capsule at this point, and it launches on an expendable booster anyway so the cost savings are minimal.

[tater]

2 minutes ago, Ol’ Musky Boi said:

Conceptually the Dreamchaser spacecraft has been around for a while. It's design heritage goes all the way back to the soviet counterparts of the cancelled X-20 Dyna-soar... in the 1970s! However as far as spaceplanes go it's a practical design: it can land on conventional runways, fit in a fairing etc. I'm not sure how much it'll "revolutionise" space travel though, given that it's effectively just a reusable cargo capsule at this point, and it launches on an expendable booster anyway so the cost savings are minimal.

At least it's launch vehicle agnostic. So it can always be put on top of F9, and then only S2 is expended. The cost issue also depends on how much refurbishment it requires itself between flights.

 

[Ol’ Musky Boi]

1 minute ago, tater said:

At least it's launch vehicle agnostic. So it can always be put on top of F9, and then only S2 is expended. The cost issue also depends on how much refurbishment it requires itself between flights.

 

Thats true, it is a very versatile system - much like the CST-100 is designed for multiple launch vehicles (I'm sensing a pattern here).

[tater]

2 minutes ago, Ol’ Musky Boi said:

Thats true, it is a very versatile system - much like the CST-100 is designed for multiple launch vehicles (I'm sensing a pattern here).

Yeah, this is a sensible choice for crew vehicles. In the case of SNC, since they are not part of a company making LVs, they have little choice. SNC is also working on expandable habitats (like Bigelow). Presumably they're smarter than Bigelow and will also make those LV agnostic. Bigelow is disappointing, they are stuck with ULA, and indeed with Vulcan at this point.

[tater]

 

[SRB]

On 3/23/2019 at 11:23 AM, Ol’ Musky Boi said:

Thats true, it is a very versatile system - much like the CST-100 is designed for multiple launch vehicles (I'm sensing a pattern here).

But will SpaceX let a non-Crew Dragon vehicle fly on F9?

[mikegarrison]

2 hours ago, ErinBensen said:

But will SpaceX let a non-Crew Dragon vehicle fly on F9?

They will if they ever get F9 launch rates high enough. It would be stupid to have a potential money-making rocket just sitting around with no mission.

[tater]

On 4/28/2019 at 9:20 PM, ErinBensen said:

But will SpaceX let a non-Crew Dragon vehicle fly on F9?

Why not? It's a customer, and not really competition for launch at all, nor for a while for crew.

[tater]

Announcement in an hour, but rocket in pic is Vulcan.

[tater]

 

You can ask questions, presser is live now...

 

[Wjolcz]

I like the way it looks. At the same time I'm still not a fan of the increased complexity of lifting bodies. I guess regular capsules need service modules too, but why not make it more like the X-37? The capabilities are probably not the same (and the complexity might be actually increased, but I don't know the details of each approach) but at least you don't need an expendable service module each time you launch.

Edited August 14, 2019 by Wjolcz

[mikegarrison]

9 minutes ago, Wjolcz said:

I'm still not a fan of the increased complexity of lifting bodies.

With the possible exception of nuclear warheads, isn't every re-entry vehicle a lifting body?

[Wjolcz]

10 minutes ago, mikegarrison said:

With the possible exception of nuclear warheads, isn't every re-entry vehicle a lifting body?

Well, I guess it depends on the definition. What I mean is I feel like there's been way more research done with designs that clearly have wings attached to their main body (X-37 in which you can tell where the wing ends and where the body starts) and more complex shapes like lifting bodies with blended wings (the 'less of a cone, more of a plane' type of vehicle).

What I'm trying to say is basically that I feel like the DreamChaser is more aerodynamically complicated than the X-37.

[tater]

Capsules do lifting entries, but I generally think of HL-10, etc when someone says “lifting body,” vs a capsule which is generally symmetric about the entry angle, vs having a dorsal and ventral that differ.

Makes me want to look up the real definition now.

[Scotius]

But doesn't it simplify the construction? Normally you have wings attached to the hull. Lifting body craft is the hull... and the wing... at the same time. No attachment points, airframe can be made as one element (more or less). Besides, it's not like Dream Chaser will have to do any extreme maneuvering in the atmosphere - it just needs to be stable in flight and be a decent glider.

[mikegarrison]

38 minutes ago, Scotius said:

But doesn't it simplify the construction? Normally you have wings attached to the hull.

It all depends, but it's pretty typical on airplanes that it's more the other way around -- the fuselage is attached to the wing. Typically the "wing box" where the wings come together is the strongest structure in the airplane, other than possibly the landing gear.

 

[tater]

That vid is awesome. I liked the mirror finish right before they fully painted it, actually.

[mikegarrison]

4 minutes ago, tater said:

That vid is awesome. I liked the mirror finish right before they fully painted it, actually.

For a while it was trendy to leave airplanes unpainted and go with the bare aluminum look. (It also saved weight.) But as more and more composites replaced aluminum, that became less and less of an option.

[tater]

2 hours ago, mikegarrison said:

For a while it was trendy to leave airplanes unpainted and go with the bare aluminum look. (It also saved weight.) But as more and more composites replaced aluminum, that became less and less of an option.

Heh, was trendy for Boeing a long time ago, as well...

 

(can't read the name in this pic, but the ship is "Aluminum Overcast")

[mikegarrison]

We are getting off-topic, but B-17s were painted until 1944. The Air Corps stopped painting them then (except for insignia), in the interests of manufacturing speed.

There was also this one:

Somehow it got started that the workers would sign it, and the idea caught on. I'm not sure if my grandfather signed that or not. He built B-17s, but at some point he had shifted to building B-29s.

Edited August 15, 2019 by mikegarrison

[tater]

I have a real image of that bird (5 Grand) flying over Europe (a friend's dad was a B-24 pilot in the war, and his friend/business partner was a dentist in the 96th BG, and I ended up with a bunch of old photos.

[tater]

Not really Dream Chaser, but...

 

[wumpus]

On 8/14/2019 at 7:30 PM, tater said:

Capsules do lifting entries, but I generally think of HL-10, etc when someone says “lifting body,” vs a capsule which is generally symmetric about the entry angle, vs having a dorsal and ventral that differ.

Makes me want to look up the real definition now.

I'd assume a "real" definition includes lift>weight, but that might include the Apollo capsule (the drag *should* disqualify it, but I doubt that is formally defined).  I'm pretty sure that it was designed to skip through the atmosphere to a higher orbit and then come down again (all to reduce maximum heating).  I don't think that was ever done in a real mission (they angled it, but not enough to leave the atmosphere).  Of course, Apollo had a much higher velocity than any other returning spacecraft, so had an amazing lift advantage just by moving the center of mass away from the center of drag.

[mikegarrison]

2 hours ago, wumpus said:

I'd assume a "real" definition includes lift>weight, but that might include the Apollo capsule (the drag *should* disqualify it, but I doubt that is formally defined).  I'm pretty sure that it was designed to skip through the atmosphere to a higher orbit and then come down again (all to reduce maximum heating).  I don't think that was ever done in a real mission (they angled it, but not enough to leave the atmosphere).  Of course, Apollo had a much higher velocity than any other returning spacecraft, so had an amazing lift advantage just by moving the center of mass away from the center of drag.

Apollo's re-entry profile included a rise up partway through, but not skipping entirely out of the atmosphere. They had an off-center cg so they could control the lift by rolling the vehicle.