For Questions That Don't Merit Their Own Thread

[tater]

31 minutes ago, JoeSchmuckatelli said:

Where do we put stuff on these guys?

You could make a thread.

Looks like they flew something, too, which is farther than many startups have gotten.

 

[sevenperforce]

9 hours ago, tater said:

9 hours ago, JoeSchmuckatelli said:

Where do we put stuff on these guys?

You could make a thread.

Looks like they flew something, too, which is farther than many startups have gotten.

The video talks about an issue with the "oxidizer flow" so I'm guessing we're looking at a hybrid rocket with a non-toxic solid fuel?

EDIT: Yes, looks that way. This article has a video of a successful test and specifically identifies it as a hybrid rocket.

[Gargamel]

On 10/11/2022 at 10:49 AM, sevenperforce said:

I've seen research that shows sintered regolith construction to be pretty promising. No binder needed.

The flip side is that sintering takes a lot of energy.    You’re basically welding dirt.   

[Hyperspace Industries]

Why can’t we outfit old supersonic bombers (Boeing B-58 hustler, Tu-22, etc.) as passenger planes, it would probably be a not too bad ride for passengers, and I could see a market for getting somewhere ridiculously fast with reasonable seating, emergencies, politicians, so on. It would have a much smaller upfront cost than building a concorde, even though fuel would be expensive.

[kerbiloid]

11 minutes ago, Hyperspace Industries said:

Why can’t we outfit old supersonic bombers (Boeing B-58 hustler, Tu-22, etc.) as passenger planes,

At least because they are usually not pressurized, except of the crew cabins.

So, you can share the structral frame, engine, etc, but these will be two different planes based on same wireframe design.

Edited October 14, 2022 by kerbiloid

[razark]

The Convair B-58 carried its payload in an external pod, combined with a fuel tank.

 

Passengers might be slightly opposed to the bumpy landing.

[DDE]

2 hours ago, Hyperspace Industries said:

Why can’t we outfit old supersonic bombers (Boeing B-58 hustler, Tu-22, etc.) as passenger planes, it would probably be a not too bad ride for passengers, and I could see a market for getting somewhere ridiculously fast with reasonable seating, emergencies, politicians, so on. It would have a much smaller upfront cost than building a concorde, even though fuel would be expensive.

Even with such a development boost, and even with smaller airframes - I've heard of both MiG-25 and MiG-31 conversion proposals - the economics never pan out. Tiny market, huge flight hour bills.

[Hyperspace Industries]

2 hours ago, razark said:

The Convair B-58 carried its payload in an external pod, combined with a fuel tank.

 

Passengers might be slightly opposed to the bumpy landing.

Forgot about that, sorry.

3 minutes ago, DDE said:

Even with such a development boost, and even with smaller airframes - I've heard of both MiG-25 and MiG-31 conversion proposals - the economics never pan out. Tiny market, huge flight hour bills.

Naturally, of course it was too expensive. Forgot about market size, there is a market, just one so small that you basically need to run out of other markets first.

[kerbiloid]

3 hours ago, razark said:

The Convair B-58 carried its payload in an external pod, combined with a fuel tank.

 

Passengers might be slightly opposed to the bumpy landing.

 

[SunlitZelkova]

8 hours ago, Hyperspace Industries said:

Why can’t we outfit old supersonic bombers (Boeing B-58 hustler, Tu-22, etc.) as passenger planes, it would probably be a not too bad ride for passengers, and I could see a market for getting somewhere ridiculously fast with reasonable seating, emergencies, politicians, so on. It would have a much smaller upfront cost than building a concorde, even though fuel would be expensive.

It's not that dumb of an idea, the Tu-16 and Tu-95 both became airliners after all, as did the B-29, while a Tu-4 conversion was proposed too.

I think rather than any detailed engineering reasons, it is just a matter of design common sense. A bomber is designed to carry payload to a target and RTB. Not carry luggage and people, not have fancy accommodations.

In the same way that converting the Concorde into a bomber would have been silly- it would be more efficient to design a purpose built bomber- converting a bomber into an airliner is not the best choice. If you can, it is better to build a purpose built airliner. Conversions of anything- ships, fighting vehicles, aircraft- usually are lacking compared to purpose built alternatives.

An example of this is the WWII Japanese aircraft carrier Junyo. It was converted from an ocean liner that was under construction, and thus had awful handling characteristics when compared with its larger purpose built comrades. Despite being huge it also had a small aircraft capacity.

The Tu-95 became the Tu-114 out of convenience. If you have to do it it will work, but purpose built is better. Like how a Toyota Hilux does work as a combat vehicle if you have to, but a HMMWV would be better.

[darthgently]

9 hours ago, Gargamel said:

The flip side is that sintering takes a lot of energy.    You’re basically welding dirt.   

So, glass melting temps roughly.  A laser with a wavelength tuned for maximum absorption by the regolith of interest.  Maybe even multiple lasers covering several optimal wavelengths that regolith would likely present; all focused to a working zone by the sintering printhead

[Rutabaga22]

Could an expanding nozzle F-1 be a feasible upper stage engine?

Edited October 14, 2022 by Rutabaga22

[Gargamel]

15 minutes ago, darthgently said:

So, glass melting temps roughly.  A laser with a wavelength tuned for maximum absorption by the regolith of interest.  Maybe even multiple lasers covering several optimal wavelengths that regolith would likely present; all focused to a working zone by the sintering printhead

Some very quick and dirty googling has it about 50W per 2mm of area melted (That was me just scanning a number of papers to find a ballpark energy cost).  Let's scale this up to 150mm... and to think Perseverance, which can use upto 900w for operations at a time, and it's not outside the realm of possibility of a larger fabrication rover being able to do something in the future.   But that's just me, who is horrible with electrical numbers, spitballing.    I can see some unmanned drone fleet landing ahead of a long term manned mission and building the basic infrastructure of buildings that would be outfitted later by the manned mission.  An inflatable habitat, a la The Martian, being erected inside a hardened basic form could create early long term living spaces. 

My biggest concern for lasers in this type of application would be maintenance.   Keeping the parts clean enough to function while throwing loads of dirt at them would be a concern.   But that's why engineers make the big bucks!  Or so they tell me when I point out an error in their blue prints at work. 

8 minutes ago, Rutabaga22 said:

Could an expanding nozzle F-1 be a feasible upper stage engine?

There's others here who will know the number way better than I, but would the mass cost of the mechanism to make it a multi-environment engine outweigh the mass cost and simplicity of just making a dedicated upper stage?

Take a look a planes like the Concord, F-14, and F-111.  Those all had heavy mechanisms to make radical adjustments to their air frames, but at what cost?   They worked, but it's obvious there might be simpler and more efficient solutions.  

[DDE]

21 minutes ago, Rutabaga22 said:

Could an expanding nozzle F-1 be a feasible upper stage engine?

"Feasible" is a low barrier, so yes. The US wouldn't have much trouble coming up with a hydrolox upper stage instead, of course, but if you lock yourself into a kerolox design, an appropriately modified version wouod work. Both candidate designs for SSMEs also used to feature expanding nozzles before another wave of cost cuts, so it sounds like this option is on the table.

What worries me is the start sequence. F-1 uses a tank head start (propellants coming down the likes under gravity) with an external unit powering the hydraulics throughout the starting sequence.

[Rutabaga22]

1 minute ago, DDE said:

F-1 uses a tank head start (propellants coming down the likes under gravity) with an external unit powering the hydraulics throughout the starting sequence.

couldn't you use ullage motors or pressure feeding for this?

[razark]

5 hours ago, SunlitZelkova said:

It's not that dumb of an idea, the Tu-16 and Tu-95 both became airliners after all, as did the B-29, while a Tu-4 conversion was proposed too.

Well, if you're going to bring reality into it (), there actually was a proposed B-58 airliner version. 

It was based on a (again, only proposed) version of the B-58, using an enlarged version with SR-71 engines.

 

 

Quote

...a version of the bomber using a five-passenger version of its unique external weapons pod...

This just amuses me.

[wumpus]

41 minutes ago, razark said:

Well, if you're going to bring reality into it (), there actually was a proposed B-58 airliner version. 

It was based on a (again, only proposed) version of the B-58, using an enlarged version with SR-71 engines.

 

Did they think the Soviets were going to sell them that much titanium *twice*?

Bomber pilots get promoted to general and demand that they get some seriously fancy toys as well...

[sevenperforce]

10 hours ago, Rutabaga22 said:

Could an expanding nozzle F-1 be a feasible upper stage engine?

An appropriately sized vacuum nozzle for an F-1 engine would need a nozzle exit area of approximately 431 square meters. Diameter of 11.7 meters, 40% larger than the diameter of the SLS.

I dunno what insane rocket you're going to have as a first stage if you have that ginormous thing as a second stage.

[DDE]

10 hours ago, Rutabaga22 said:

couldn't you use ullage motors or pressure feeding for this?

Both would be enormously overdesigned compared to normal. You'd need to replace a whopping 1 g of acceleration, which would mean either huge ullage motors or a very overdesigned tanks to sustain an abnormally high pressure.

[kerbiloid]

3 hours ago, sevenperforce said:

Diameter of 11.7 meters, 40% larger than the diameter of the SLS

Spoiler

3 hours ago, DDE said:

Both would be enormously overdesigned compared to normal. You'd need to replace a whopping 1 g of acceleration, which would mean either huge ullage motors or a very overdesigned tanks to sustain an abnormally high pressure.

Back to the advantage of the turbopump steering nozzles over the gymbal.

[TheSaint]

On 10/14/2022 at 6:25 AM, razark said:

Passengers might be slightly opposed to the bumpy landing.

[magnemoe]

21 hours ago, SunlitZelkova said:

It's not that dumb of an idea, the Tu-16 and Tu-95 both became airliners after all, as did the B-29, while a Tu-4 conversion was proposed too.

I think rather than any detailed engineering reasons, it is just a matter of design common sense. A bomber is designed to carry payload to a target and RTB. Not carry luggage and people, not have fancy accommodations.

In the same way that converting the Concorde into a bomber would have been silly- it would be more efficient to design a purpose built bomber- converting a bomber into an airliner is not the best choice. If you can, it is better to build a purpose built airliner. Conversions of anything- ships, fighting vehicles, aircraft- usually are lacking compared to purpose built alternatives.

An example of this is the WWII Japanese aircraft carrier Junyo. It was converted from an ocean liner that was under construction, and thus had awful handling characteristics when compared with its larger purpose built comrades. Despite being huge it also had a small aircraft capacity.

The Tu-95 became the Tu-114 out of convenience. If you have to do it it will work, but purpose built is better. Like how a Toyota Hilux does work as a combat vehicle if you have to, but a HMMWV would be better.

Yes, bombers have small bomb bays compared to cargo hold on a transport plane or passenger plane as bombs are heavy.  The large bomb bay doors on the other hand make an weak point within the wingbox who need to be heavier to handle this, removing the doors don't help much here Now you could make an supersonic private jet out of it. 

An more practical idea was to use the wings, engines and landing gear from an bomber but make the fuselage larger, its not an converted plane its an new one but one who use lots of shared parts.
This was done with multiple US bomber designs. 

[kerbiloid]

Just on a close topic.

https://thebulletin.org/2021/11/the-untold-story-of-the-worlds-biggest-nuclear-bomb/

Some roomy designs.

[Rutabaga22]

Wouldn't near C interstellar travel be deadly to a human?

The Gs of going near C would turn you into a spray of red, right? 

Shouldn't the Alcubierre Drive be the "Alcubierre Death Machine"?

[Terwin]

17 minutes ago, Rutabaga22 said:

Wouldn't near C interstellar travel be deadly to a human?

The Gs of going near C would turn you into a spray of red, right? 

Shouldn't the Alcubierre Drive be the "Alcubierre Death Machine"?

It depends on how fast you accelerate, and how you accelerate.

With an Albercurrie drive you don't accelerate.  You should not even feel as though you are moving, so how could that crush or compress you?  (the space around you is moving relative to other space, but you are not moving relative to it)

If you are going near c, and are struck by a mass without protection, then that would be bad, but generally you are inside of an enclosed space which is maintaining your atmosphere, so presumably the enclosure would take any damage from stray bits of matter, not the passenger.

If you use a gravity drive to accelerate at several G, then you may suffer some inner-ear discomfort if the gravitational gradient is uneven, but otherwise you would be fine(it would be the same as falling towards a planet with no atmosphere and then missing, you would not feel any acceleration at all, as opposed to a car when you hit the gas)

If you use a reaction engine to push your vessel forwards(like a rocket), then you need to be careful how hard you push, as you will feel the acceleration, and accelerating too fast can be harmful to humans(it feels identical to gravity, and a few dozen Gs will crush a person to death in short order), but if you accelerate slowly enough(say 0-2 G of acceleration), then you should be fine even if you accelerate up to near-c velocities.