I would note, though, that the idea of transpiration cooling has been around for a long time. It’s just never been implemented. But I guess what he’s saying has never been proposed before is the structure also serving as heat shield.
[Update a while later]
New Glenn has been redesigned. Looks like the upper stage is expendable.
Looks like they were inspired in part by Falcon 9. It’s interesting that we’re starting to see spacecraft designs converging, as aircraft designs did in the thirties.
Re structure as heat shield, what about von Braun’s proposed winged rocketships from the 1950’s? They were to have been made of stainless steel. I don’t think there was any transpiration cooling, though.
Re structure as heat shield, what about von Braun’s proposed winged rocketships from the 1950’s? They were to have been made of stainless steel, and I don’t think there were separate heat shields (could be wrong). No transpiration cooling, though.
From the linked article:
As far as we know, this marks the first time the material has been used in spacecraft construction since some early, ill-fated attempts during the Atlas program in the late 1950s.
Ill-fated attempts? How about resounding success?
Yes, that was badly stated. There have been a few dramatic examples of Atlas balloon tank failure, but the vehicle in general was quite successful. The Centaur (Atlas V upper stage) still uses stainless steel balloon tanks, doesn’t it?
It got John Glenn to orbit.
Yes, the Centaur tanks are stainless steel.
Re New Glenn, Here is their video from two years ago. Differences I spot are:
* Wider stance (SpaceX-ish) landing legs.
* Full diameter fairing. (The moved up to 7m from 5.4m was announced in September 2017.)
* Two upper stage engines instead of one. The earlier rendering shows a lot more substantial engine detail. Had their initial plan been to use a vacuum version of their combustion tap-off cycle BE-3, but then changed to two open expander cycle BE-3U engines?
“wider stance”
Cue Larry Craig joke.
Rand, do you recall back at RotRock 20 years ago the sample panel of aluminum transpiration cooled heat shield made by platelet bonding? I hope Gary still has it.
Yes, vaguely. He probably does.
My understanding is that the upper stages of New Glenn have always been expendable. New Armstrong is supposed to have a reusable upper stage.
The stainless steel Atlas is second only to Soyuz as the most-flown rocket in history (if one counts the R-7 on as the “Soyuz” family). Hardly an “ill-fated” set of attempts.
Yeah, 301 is not only strong, it can be super-strong. ARDE made a huge business out of cryostretching 301 pressure vessels. The process involves filling the vessel with liquid nitrogen, then pressurizing it to the point where the material strains by 7%. That converts the austenitic 301 into a martensitic grain structure. An even more amazing outcome is that the resulting pressure vessel has the property of leak-before-burst, an ideal safety feature. From the standpoint of fracture mechanics, it’s hard to beat cryostretched 301. We used it for the Peacekeeper Stage IV helium tank, after a brief flirtation with the (much) more expensive PSI 6Al-4V titanium tank (which was not leak-before-burst). This will be interesting.
BTW, the X-15, B-52 Hustler, and XB-70 were all mostly stainless steel of one brand or another. The Dyna-Soar was entirely Rene 41, built on a statically determinate frame (to eliminate thermal expansion issues – a scary way to do it, I might add).
I forgot to add that the 0.2% yield stress goes from 140 ksi in the full hard condition to about 182 ksi in the cryostretched state.
That was the B-58 Hustler. You could also mention the Mig 25 Foxbat and it’s descendants. The X-15 was made of Inconel X. Calling that “stainless steel” is a bit of a stretch. Steel is dominantly iron. The Inconel family of alloys is dominantly nickel and cobalt. Most of the alloys in the Inconel family have 10% or less iron content. The alloy family name, in fact, is derived from Inco, the International Nickel Company which has been mining the buried remnant of the ancient Sudbury, Ontario nickel-iron asteroid strike for decades.
Good catch on the B-58, thanks. (I could say that I was only off 10%, good enough for government work – but I won’t.)
Yes, Inconel is not formally considered a stainless steel, though it is often referred to as such by those who work with it. Milt Thompson refers to it as “steel” in At The Edge of Space: The X-15 Story.”
Other differences vs. Al:
Modulus of elasticity is 3x, deflection is often more limiting than strength in large structures.
Coefficient of thermal expansion 1/3.
Much (x1/5?) lower thermal conductivity.
Far easier to fabricate by welding. Al weldments must be heat treated as a whole or the heat affected zone reverts to the as wrought properties that are a fraction of the heat treated strength.
Much easier to insure the integrity versus composite. You can stretch, bend or break a piece from the same lot of metal and be reasonably sure that the material in your structure will behave the same way. Composites are much more dependent on every step of a long process being done exactly right. It isn’t that it can’t be done but it’s not cheap.
Is your statement about weldability still true now that Al has FSW? I understand that was a game changer for aluminum alloys.
It shouldn’t apply to FSW weldments as there is no actual melting involved in that process.
It may not, I don’t know. The critical temperature for some alloys/heat treatments is as low as 400°F. FSW didn’t exist when I was last concerned with this. The videos I’ve seen show the stirrer bright red, about 1500° or better. The bulk of the base metal is much cooler and there are a lot of alloys and heat treatments.
All of the examples I’ve seen are of joining plates edge to edge, which is great for tanks. I don’t know if it can be applied to more varied sorts of joints.
Back when Boeing was building B52’s. They needed an autoclave big enough to heat treat the entire main spar in one piece. Heat treating Al is fairly involved with different critical temperatures separated by ramps and soaks and has to be done in a controlled space.
Transpiration cooling has been attempted several times but it has mostly failed in practice. I thought I heard they were going to just flow the propellant underneath the skin and vent it off board though?
I guess film cooling is used in rocket nozzles and it does work there.
What were the failures?
My guess would be you need to ensure the system to pump it is reliable enough, considering losing it during reentry would could result in anything from damage to catastrophic loss. Not saying it can’t work, but going from something that will work as long as it doesn’t get a hole in it like Columbia, to something with moving parts can often result in more failures. I’m assuming whatever pumps and equipment will have double or triple redundancy. But I’m not an engineer so take my comment with a grain of salt.
I would worry about localized spots running dry either through poor coolant distribution or overly intense heating. How do you spread coolant through the entire area that needs it? A fascinating engineering project indeed.
To be honest, I was always very skeptical on the reliability of using massive composite tanks and structures, especially for long duration and thermally demanding purposes. I also figured that getting that developed would be a lot more time-consuming than imagined.
My initial take on the stainless steel Starship concept is it’s very innovative, with a great many advantages.
Speaking of SpaceX, just why is a director of public affairs for Texas Railroad Commissioner Ryan Sitton writing anti-SpaceX op-eds in The Hill?
https://thehill.com/opinion/technology/426463-is-the-space-industry-moving-beyond-spacex
As Eric Berger tweets, almost every point he makes is wrong, sometimes ridiculously so. And it does make you wonder who is really behind it.
Didn’t the Apollo CM use a structure of stainless steel honeycomb panels? Similar to the XB-70 bomber?
The nose section of the test vehicle (removed to install tanks etc) was blown over and damaged by high winds last night. Musk says will take a few weeks to repair.
Not much to see, but here is a photo of the downed nose section: https://forum.nasaspaceflight.com/index.php?topic=47120.msg1904507#msg1904507