4 ms·

All of these hypersonics companies are targeting mach 5 for a reason, which is that the material science hasnt caught up yet. The bet seems to be that they'll e

All of these hypersonics companies are targeting mach 5 for a reason, which is that the material science hasnt caught up yet. The bet seems to be that they'll either be ready once it is, or they'll be the ones to develop it and start raking in a mountain of military industrial complex cheese. Not a bad goal, but the thin vernier of 'passenger flight' leaves a bad taste in my mouth. This tech is for munitions delivery first, the meatbag ferry is squarely a side hustle, and I wish they'd be honest about it.

Havoc 3y ago
A fair bit of vehicles go well north of 5 already so propulsion aside I don’t think the hurdles are massive. And propulsion seems to be what everyone is focused on
nordsieck 3y ago
> All of these hypersonics companies are targeting mach 5 for a reason, which is that the material science hasnt caught up yet. My understanding is that mach ~5 is when ramjets hit their limit and you have to transition to scramjets if you want to go faster.
- MilStdJunkie 3y ago
  That's also right around where aerodynamic forces are juuuuuuust starting to transition to disassociation and ionization in high flow areas, as the electrons are ripped from molecules in the air. Probably not a coincidence, because a very ooooof zone will be the ramjet intake, since ramjets need to slow the air to subsonic for combustion. Lots of these high mach ramjets have amazing cooling devices on the intake. These RDEs are especially neat because the exhaust mass is moving supersonically but they're very choosy about the mix in the combustion chamber, so and air-breathing RDE will be doing some sort of voodoo in that department. If they riddle it out they might get a single engine that functions throughout the airspeed regime.
IntrepidWorm 3y ago
It does feel disingenuous, but its also nothing new. Military research has always been the one of the primary driving forces behind critical technology. Commercial tech is vulnerable to all sorts of disruptions, regulations, and setbacks. If you make something that will make killing a whole bunch of people easier, rest assured theres a global market for it.
- deleted 3y ago
  [deleted]
alex_young 3y ago
Are they targeting Mach 5? The second paragraph of TFA says "The company's long-term ambition is to develop a commercial aircraft that can travel at Mach 9". They mention that goal a couple of places, and state that hypersonic is defined as Mach 5 or more.
AnarchismIsCool 3y ago
I'm in the industry... It's a constant psychological game. The type of highly educated people necessary to pull off these ventures are less interested in being part of the MIC than they used to be. Nationalism in that crowd is thankfully much less aggressive than it was during the cold war. As such, founders have resorted to lying about their goals so they can expand their applicant pool for developing the tech, then "pivot" and get acquired by Raytheon et al. I also think to some extent there are employees who know but semi-appreciate the cover. In a prior life, I worked on some stuff that's, unfortunately, currently being used to murder people in the middle east. That just doesn't make good small talk at parties.
- eschneider 3y ago
  Rest assured, founders who'll lie to their applicant pool about that will lie to their applicant pool about anything inconvenient.
- buildsjets 3y ago
  It may have hurt me financially and limited my career opportunities, but this is one reason why I refuse to work on any technology that requires me to have a security clearance. It's a decision I made way back at the end of the last century and it has served me well throughout ~25 years of aircraft development while the world has been at continuous war, and mostly kept me out of military programs. Also, I took one look at the SF86 and said F that, no government deserves that information, so I didn't get screwed in the Department of State OPM hack like all the other suckers.
  - JumpCrisscross 3y ago
    > may have hurt me financially and limited my career Weapons doesn’t pay as well as making people click ads. The people working on this stuff are usually doing so because they believe it’s the right thing.
    - shiroiushi 3y ago
      Actually, working for DOD programs has several advantages: 1) The pay is pretty good. It's not FAANG-level pay, but it's generally better than non-FAANG pay, without so much competition. 2) The work-life balance is excellent, as long as it's in a place you want to live. No 80-hour weeks, as overtime is generally prohibited unless approved by the customer (and then you get overtime pay). Time is tracked and paid by the government on an hourly basis, so they don't allow overtime unless necessary. No unpaid "exempt" overtime. 3) Generally stable employment. It's hard to find people with a security clearance, so it's hard to get fired unless you're a really poor performer. You probably don't have to worry about dealing with stack ranking unlike many regular jobs.
throwaway2562 3y ago
Agreed, this has nothing to do with passenger flight, and the pretense is gross. Thin vernier -> thin veneer btw
credit_guy 3y ago
No. A lot of hypersonic stuff is partly classified. So the journalists are left with the definition: hypersonic speed is Mach 5 and higher. Mach 5 is where the heat produced in the boundary layer (by compression, mainly) is high enough that chemical reactions take place and you need to account for them in your computational fluid dynamics. As a rule of thumb, when you hear boost-glide vehicle, the speed is close to Mach 20. If it’s air breathing (ramjet or scramjet) the speed is slightly higher than Mach 5, but probably less than Mach 10.
euroderf 3y ago
I appreciate the sentiment, but it sounds a bit like the case of I.T. vis-à-vis the NSA. As James Bamford said, one expects+assumes that the NSA is way ahead of the state of the civilian art. They have the budget. Likewise this case. As an OTL civvie I'd expect that this tech under discussion lags whatever .mil is up to. Out to launch!
- axus 3y ago
  Maybe they can catch up and end up with a more cost-effective rocket, like SpaceX. But probably not.
jandrewrogers 3y ago
You could make the same argument for a lot of software tech startups. If you develop state-of-the-art data infrastructure software, novel data processing capabilities, or some other advanced software tech, it is routine to have an org under the US DoD as one of the earliest pilot customers. It is an open secret but many startups pretend like this isn't a standard part of that kind of business. The US DoD is a sophisticated early adopter of a lot of tech at a stage before most commercial enterprises are willing to engage. The average person on the street may be a bit naive about this but the majority of deep tech startups are de facto "dual use" and none of this should be a surprise to someone that works in deep tech.
JumpCrisscross 3y ago
> mach 5 for a reason, which is that the material science hasnt caught up yet The X-15 did Mach 6 in the 60s. What materials and components are you referring to as cliffing us at Mach 5? Isn’t the simpler explanation that hypersonic flight is defined at Mach 5?
- jtriangle 3y ago
  The X-15's had to be repainted after every flight, because the ablative coating was designed to wear off at speed. That's a huge expense, in both time and money. Worth it for a research craft, not worth it for any practical use. In terms of materials, most of the newmake ultra fast aircraft are using inconel, which is more viable than it was back in the day. Some are using ceramic coatings of various sorts in hopes that they'll be able to develop something strong enough to be reused. And that's not to say that they won't be able to come up with something, just that nobody has done it yet, or, has done it and has talked about it.
  - JumpCrisscross 3y ago
    I’m not saying we don’t have work to do on materials. I’m narrowly pushing back on the assertion that these materials cause the Mach 5 threshold.

Havoc 3y ago

A fair bit of vehicles go well north of 5 already so propulsion aside I don’t think the hurdles are massive. And propulsion seems to be what everyone is focused on

nordsieck 3y ago

> All of these hypersonics companies are targeting mach 5 for a reason, which is that the material science hasnt caught up yet. My understanding is that mach ~5 is when ramjets hit their limit and you have to transition to scramjets if you want to go faster.

MilStdJunkie 3y ago
That's also right around where aerodynamic forces are juuuuuuust starting to transition to disassociation and ionization in high flow areas, as the electrons are ripped from molecules in the air. Probably not a coincidence, because a very ooooof zone will be the ramjet intake, since ramjets need to slow the air to subsonic for combustion. Lots of these high mach ramjets have amazing cooling devices on the intake. These RDEs are especially neat because the exhaust mass is moving supersonically but they're very choosy about the mix in the combustion chamber, so and air-breathing RDE will be doing some sort of voodoo in that department. If they riddle it out they might get a single engine that functions throughout the airspeed regime.

IntrepidWorm 3y ago

It does feel disingenuous, but its also nothing new. Military research has always been the one of the primary driving forces behind critical technology. Commercial tech is vulnerable to all sorts of disruptions, regulations, and setbacks. If you make something that will make killing a whole bunch of people easier, rest assured theres a global market for it.

deleted 3y ago
[deleted]

alex_young 3y ago

Are they targeting Mach 5? The second paragraph of TFA says "The company's long-term ambition is to develop a commercial aircraft that can travel at Mach 9". They mention that goal a couple of places, and state that hypersonic is defined as Mach 5 or more.

AnarchismIsCool 3y ago

I'm in the industry... It's a constant psychological game. The type of highly educated people necessary to pull off these ventures are less interested in being part of the MIC than they used to be. Nationalism in that crowd is thankfully much less aggressive than it was during the cold war. As such, founders have resorted to lying about their goals so they can expand their applicant pool for developing the tech, then "pivot" and get acquired by Raytheon et al. I also think to some extent there are employees who know but semi-appreciate the cover. In a prior life, I worked on some stuff that's, unfortunately, currently being used to murder people in the middle east. That just doesn't make good small talk at parties.

eschneider 3y ago
Rest assured, founders who'll lie to their applicant pool about that will lie to their applicant pool about anything inconvenient.
buildsjets 3y ago
It may have hurt me financially and limited my career opportunities, but this is one reason why I refuse to work on any technology that requires me to have a security clearance. It's a decision I made way back at the end of the last century and it has served me well throughout ~25 years of aircraft development while the world has been at continuous war, and mostly kept me out of military programs. Also, I took one look at the SF86 and said F that, no government deserves that information, so I didn't get screwed in the Department of State OPM hack like all the other suckers.
- JumpCrisscross 3y ago
  > may have hurt me financially and limited my career Weapons doesn’t pay as well as making people click ads. The people working on this stuff are usually doing so because they believe it’s the right thing.
  - shiroiushi 3y ago
    Actually, working for DOD programs has several advantages: 1) The pay is pretty good. It's not FAANG-level pay, but it's generally better than non-FAANG pay, without so much competition. 2) The work-life balance is excellent, as long as it's in a place you want to live. No 80-hour weeks, as overtime is generally prohibited unless approved by the customer (and then you get overtime pay). Time is tracked and paid by the government on an hourly basis, so they don't allow overtime unless necessary. No unpaid "exempt" overtime. 3) Generally stable employment. It's hard to find people with a security clearance, so it's hard to get fired unless you're a really poor performer. You probably don't have to worry about dealing with stack ranking unlike many regular jobs.

throwaway2562 3y ago

Agreed, this has nothing to do with passenger flight, and the pretense is gross. Thin vernier -> thin veneer btw

credit_guy 3y ago

No. A lot of hypersonic stuff is partly classified. So the journalists are left with the definition: hypersonic speed is Mach 5 and higher. Mach 5 is where the heat produced in the boundary layer (by compression, mainly) is high enough that chemical reactions take place and you need to account for them in your computational fluid dynamics. As a rule of thumb, when you hear boost-glide vehicle, the speed is close to Mach 20. If it’s air breathing (ramjet or scramjet) the speed is slightly higher than Mach 5, but probably less than Mach 10.

euroderf 3y ago

I appreciate the sentiment, but it sounds a bit like the case of I.T. vis-à-vis the NSA. As James Bamford said, one expects+assumes that the NSA is way ahead of the state of the civilian art. They have the budget. Likewise this case. As an OTL civvie I'd expect that this tech under discussion lags whatever .mil is up to. Out to launch!

axus 3y ago
Maybe they can catch up and end up with a more cost-effective rocket, like SpaceX. But probably not.

jandrewrogers 3y ago

You could make the same argument for a lot of software tech startups. If you develop state-of-the-art data infrastructure software, novel data processing capabilities, or some other advanced software tech, it is routine to have an org under the US DoD as one of the earliest pilot customers. It is an open secret but many startups pretend like this isn't a standard part of that kind of business. The US DoD is a sophisticated early adopter of a lot of tech at a stage before most commercial enterprises are willing to engage. The average person on the street may be a bit naive about this but the majority of deep tech startups are de facto "dual use" and none of this should be a surprise to someone that works in deep tech.

JumpCrisscross 3y ago

> mach 5 for a reason, which is that the material science hasnt caught up yet The X-15 did Mach 6 in the 60s. What materials and components are you referring to as cliffing us at Mach 5? Isn’t the simpler explanation that hypersonic flight is defined at Mach 5?

jtriangle 3y ago
The X-15's had to be repainted after every flight, because the ablative coating was designed to wear off at speed. That's a huge expense, in both time and money. Worth it for a research craft, not worth it for any practical use. In terms of materials, most of the newmake ultra fast aircraft are using inconel, which is more viable than it was back in the day. Some are using ceramic coatings of various sorts in hopes that they'll be able to develop something strong enough to be reused. And that's not to say that they won't be able to come up with something, just that nobody has done it yet, or, has done it and has talked about it.
- JumpCrisscross 3y ago
  I’m not saying we don’t have work to do on materials. I’m narrowly pushing back on the assertion that these materials cause the Mach 5 threshold.