Surface to orbit spacecraft discussion from prometheuspan’s intro thread

[Pyrotex]

Moderation note: the first 6 post of this thread were moved from the introduction thread 23035, because they’re a space discussion.

 

For 25 years, I designed and built complex software systems. Mostly for the Shuttle Simulators (astronaut flight trainers) and the Space Station. Now I invent mathematical models for estimating the reliability of software systems.

 

I'm not very thrilled with the Constellation Program, starting with the ARES-1. But then, Constellation just got cancelled (mostly) so it's a moot point.

 

The biggest number-one problem we HAVE to solve is reducing the cost of getting into space. The Saturn booster (Apollo program) could put stuff into orbit at about $5,000 a pound. The Shuttle can do it for about $25,000 a pound. Way too expensive. If we cannot bring the cost down below $5,000 a pound, we won't have a manned space program very much longer.

 

To lower costs, you make things simple. That doesn't mean you have to go 1970's. If we built a new, improved Saturn booster today, we could make it safer and cheaper, and stronger. If we used Shuttle external tanks and engines and solid rocket boosters, but no Shuttle, we could be even safer and stronger, and much cheaper. The Research and Development (R&D) is the most expensive thing about making a new rocket system.

 

So, I would vote against space planes and ram rockets. The R&D to make them work safely would be billions and billions of $. Too complicated. Too much to go wrong.

 

The real trouble is, all the aerospace companies know that R&D is where the profit is. They are gonna want the fanciest, most complicated, sexiest looking rocket plane they can think of. :confused: But we taxpayers can't afford that. We can't even afford the Shuttle. Our space program is going nowhere until we reduce the cost of getting into space. And if that means an "ugly" rocket system then so be it.

[prometheuspan]

For 25 years, I designed and built complex software systems. Mostly for the Shuttle Simulators (astronaut flight trainers) and the Space Station. "

 

please tell me that we can play together in autocad and sketchup?

:confused:;):D:bow::biggringift:

 

 

Now I invent mathematical models for estimating the reliability of software systems.

 

hmm.

 

I'm not very thrilled with the Constellation Program, starting with the ARES-1. But then, Constellation just got cancelled (mostly) so it's a moot point.

 

well, exactly so, and then, "whats next"?

 

 

The biggest number-one problem we HAVE to solve is reducing the cost of getting into space. The Saturn booster (Apollo program) could put stuff into orbit at about $5,000 a pound. The Shuttle can do it for about $25,000 a pound. Way too expensive. If we cannot bring the cost down below $5,000 a pound, we won't have a manned space program very much longer.

 

To lower costs, you make things simple. That doesn't mean you have to go 1970's. If we built a new, improved Saturn booster today, we could make it safer and cheaper, and stronger. If we used Shuttle external tanks and engines and solid rocket boosters, but no Shuttle, we could be even safer and stronger, and much cheaper. The Research and Development (R&D) is the most expensive thing about making a new rocket system.

 

So, I would vote against space planes and ram rockets. The R&D to make them work safely would be billions and billions of $. Too complicated. Too much to go wrong.

------------

 

 

Ah. but. see. the blockage?

 

Why you carry big heavy metal tanks? to carry your fuel. why they weigh so much?

have to be pressurized. Whats inside of em? liquid compressed gasses. Which.

are also present in the atmsophere.

 

You answered your own question or objection and didn't even see it.

 

All of your cost stuff ? Yo? exactly my point. So i think this thing should land and refuel on

sea water and distil that into garbage, oxygen, and hydrogen, and explosively refrrigerated

and compressed there after, off you go.

 

but those tanks shrink, because all they have to do is deliver you to mach speed where ramrockets get compression, and then above atmosphere for the space ram higher velocity need for the space ram rockets.

 

Your problem is low technology built dino huge and costing so much money.

 

i tell you the answer and you think R+D is in the billions. Well, it must be if you did it your way.

 

Maybe we should try a few change on your way. like for instance, open source design;

using this forum and sketchup.

 

What if you really did let mass intelligence do some foot work for NASA?

 

see where i am getting at?

 

have you ever thought to yourself...

 

how would somebody lead the public on a good thought experiment to do this...

??

 

and even ten better...

?how as a scientist not to toss my bias into the experiment?

 

 

The real trouble is, all the aerospace companies know that R&D is where the profit is. They are gonna want the fanciest, most complicated, sexiest looking rocket plane they can think of.

 

Why don't you tell me your design criteria and I will get to work on a pragmatic non sexxy design? lol

 

 

 

:note2: But we taxpayers can't afford that. We can't even afford the Shuttle. Our space program is going nowhere until we reduce the cost of getting into space. And if that means an "ugly" rocket system then so be it.

 

 

Let me sort of repeat what i think is obvious. 4 very small but much more sophisticated thrust systems could do the same job for a tenth the cost by using the atmosphere where

thats capturable and just going green for shuttle fuel.

 

These aren't off the cuff answers, tho brief, actually, lots of thought.

 

whole thought experiments even.

 

 

You need a pre mach accelerator, a post mach atmospheric air burner, a post air

accelerator, and then a space ram rocket.

 

small like, and more fitted into a more truly elongated saucer sort of hull shape.

 

the whole thing comes off oh yes much cheaper, by not carrying the enormous tanks

and thus defeating all of that carry mass.

 

Add a nice high altitude balloon launch system, and thats another notch more expensive

like your thinking.

 

Also, we get to cut down on ground mechanical equipment costs most people never see

or think of when they think shuttle.

 

thats an enormous savings right there.

 

 

but hey, you let me know what you'd like me to draw?

:):Whistle:

[prometheuspan]

it would seem that my punishment for failing to kiss tush in the global warming thread has caused buffy

to get personal and follow me around issuing bogus warnings and notices that don't have any merit

and making personal attacks and ad hominems against me in email.

 

if anyone has any interest in contacting me to discuss anything further, my email is [email protected]

 

otherwise, I assume, I'm about to be banned, because i don't walk on eggshells or let myself be bullied

by people who are ignorant or lying.

 

Like i asked buffy;

let me see your metaprocess.

 

she has no answer because there isn't one.

 

I'd love to help ya all build it.

 

Otherwise i am going to go find places that aren't orwellian anti intellectual and where the moderators have the good sense not to try to tell me i have ago problems when I'm the aspie.

 

like here.

 

Metaprocess / Wiki (W1AA)

 

:bouquet:

[Pyrotex]

Let me sort of repeat what i think is obvious. For very small but much more sophisticated thrust systems could do the same job for a tenth the cost by using the atmosphere where thats capturable and just going green for shuttle fuel....

 

You need a pre mach accelerator,

a post mach atmospheric air burner,

a post air accelerator, and then

a space ram rocket. ...

I'm not trying to rain on your parade, really. I like your enthusiasm and creativity. Reminds me of me about 40 years ago. But I think we should look at some things first.

 

Your idea above is excellent. It's so good, in fact, that it was already tried.

I was working for McDonnell Douglas on Space Station (back in the late 1980's), when my company won a piece of the contract for the National Aerospace Plane (NASP). A lot of the high level design was being done in my building, so I got to look over a lot of shoulders.

 

It was GORGEOUS! Fuel up with liquid hydrogren and oxygen, take off from a looooong runway, cruise up to 50,000 ft, go supersonic, climb like a bat out of hell, go hypersonic, go hyperdiapersonic (that's so fast that you **** your pants), then cut in the rocket engines at 150,000 ft and push to orbit. Dream machine! It had all the components you named above.

 

Take a look at the link. From what I recall, that summary is correct.

[prometheuspan]

The mass saved by eliminating the final rocket propellants had to be balanced, however, against the mass of the active thermal management system. This system became more complex and massive at higher speeds. At some point, the additional mass of the thermal management system needed to continue the acceleration of the air breathing scramjet would become greater than the mass of the rocket motors and propellant needed to continue the ascent to orbit.

 

yes, how long ago was that? can these issues be solved better now?

 

what if we worked the problems together instead of always deciding before we start that theres no point in it?

 

Problems.. problems ...problems...

 

we can work to solve them or we can always assume they can't be solved and then

make that as real as our mental habit.

:bouquet:

 

http://scholar.google.com/scholar?hl=en&q=%22ram+rocket%22+modern+improvements&btnG=Search&as_sdt=2000&as_ylo=&as_vis=0

 

 

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V3W-497BC82-5Y&_user=10&_coverDate=12/31/1989&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1307840368&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=afbc2301a7d0b110290971dc2be1c1b1

 

 

http://books.google.com/books?hl=en&lr=&id=psiYLwW15DoC&oi=fnd&pg=PA101&dq=%22ram+rocket%22+modern+improvements+space&ots=a2Dfroz4Nd&sig=EudIj2Bxph1tvOwXOB3BZ4Cf10w#v=onepage&q&f=false

 

http://www.springerlink.com/content/kt81711787x73210/

 

 

The point of this being that you identify real problems which people have worked on and found in many cases at least partial

solutions for.

 

[CraigD]

yes, how long ago was that [the NASP]? can these issues be solved better now?

Yes, with only a few exceptions, nearly every engineering problem of the past century or so can be solved better now. However, for an engineering challenge like a 100% reusable SSTO spacecraft, solutions need not just be better than in the past – they must be good enough to actually succeed.

what if we worked the problems together instead of always deciding before we start that theres no point in it?

Efforts to design and build an economical – or even an un-economical winged SSTO aircraft are ongoing by many competent and fairly well-funded enterprises. An especially ambitious (and pretty) example is the Skylon – which, interestingly, is built around not a scramjet, but fairly conventionl, SR-71-like turboramjets integrated with a fairly conventional liquid fuel rocket motor.

 

One of my (as a space fan) personal favorite design ideas was that of the original Roton “space helicopter”, the brainchild of engineer and spaceflight cult hero Gary Hudson. Unlike the low-altitude-capable prototype (the ATV) that was actually built and flown in 1999, a little more than a year before its company failed, early designs were for a vehicle dominated by a large helicopter rotor with rocket motors in its tips, which ascended through most the lower atmosphere at well under the speed of sound, gradually transitioning into a pure rocket in which the rotors’ rotation served only to centrifugally pump fuel and oxidizer to the rocket motors. Unfortunately, detailed and/or prettily rendered sketches of this original concept are hard to find – this 1996 Wired article has a decent journalist’s text description, while images such as figure 1 of this paper by Hudson

[prometheuspan]

Yes, with only a few exceptions, nearly every engineering problem of the past century or so can be solved better now. However, for an engineering challenge like a 100% reusable SSTO spacecraft, solutions need not just be better than in the past – they must be good enough to actually succeed.

 

agreed and understood.

 

Efforts to design and build an economical – or even an un-economical winged SSTO aircraft are ongoing by many competent and fairly well-funded enterprises. An especially ambitious (and pretty) example is the Skylon – which, interestingly, is built around not a scramjet, but fairly conventionl, SR-71-like turboramjets integrated with a fairly conventional liquid fuel rocket motor.

 

One of my (as a space fan) personal favorite design ideas was that of the original Roton “space helicopter”, the brainchild of engineer and spaceflight cult hero Gary Hudson.

 

when i was a kid with legos watching airwolf, boy did i build a lot helicopters!

 

As an adult what comes to mind is you don't need a lot of surface area if you have a good

compression and burn rate or especially a strong thrust.

 

More advanced vertical lift systems are still in essence rotor blade systems but they are now incorporated into a hull and they mostly work to shove the air into the longer thrust shaft and down the rest of the air breathing ram rocket system.

 

 

 

 

Unlike the low-altitude-capable prototype (the ATV) that was actually built and flown in 1999, a little more than a year before its company failed, early designs were for a vehicle dominated by a large helicopter rotor with rocket motors in its tips, which ascended through most the lower atmosphere at well under the speed of sound, gradually transitioning into a pure rocket in which the rotors’ rotation served only to centrifugally pump fuel and oxidizer to the rocket motors. Unfortunately, detailed and/or prettily rendered sketches of this original concept are hard to find –

 

I f you come to RBEF where the formats are kind and the whole thing more me friendly i can do a post and we can go to my models. I think i have two or three actual helicopters

but mostly vectored thrust lifting bodies.

 

 

 

 

i go look now...

:Glasses:

[prometheuspan]

such as figure 1 of this paper by Hudson

 

the general concept is good, the scale is too small for the person there tho, and the whole thing

reminds me of davincis helicopter. right but still needing more work.

 

I like the plane, it looks a lot like some of the things i have drawn, tho i tend to include wider lifting

bodies and less fully cylindrical shape.

 

I just started a thread on architecture, come on over and start one on space planes?

 

PANZ Design Collaborative

[Boerseun]

Interesting link about the NASP, Pyro.

 

Have I got it right that the only thing preventing it from reaching Mach 25 without rockets is thermal management? In which case advanced materials science might still come to its rescue yet?

 

I don't think the difficulty of finding a mission for it (as stated in the end of the article) quite jibes. If you have an airplane that can go orbital, I'm sure you will have no problem finding a mission for it - be it military or civilian.

 

So the bottom line is materials science, by the look of things. That, and mass hydrogen production (to make it feasible in the civilian economy. The military don't care to spend $40,000 on a toilet seat, so expensive hydrogen production won't bother them).

[Turtle]

...

I don't think the difficulty of finding a mission for it (as stated in the end of the article) quite jibes. If you have an airplane that can go orbital, I'm sure you will have no problem finding a mission for it - be it military or civilian.

 

So the bottom line is materials science, by the look of things. That, and mass hydrogen production (to make it feasible in the civilian economy. The military don't care to spend $40,000 on a toilet seat, so expensive hydrogen production won't bother them).

 

as long as it doesn't have to carry peeps, the air force has got a new little number up just recently. :shrug:

 

 

mysterious unmanned U.S. military spacecraft, known as the X-37B Orbital Test Vehicle, has been launched on its maiden voyage.

 

It was launched off an Atlas Five rocket shortly before 8 p.m. ET Thursday from Cape Canaveral, Fla., the U.S. air force said in a statement issued the same night.

 

Mystery has swirled as the force has released little information about the aircraft, which is reusable and similar to a small space shuttle.

 

Likened to the size of a sports car with an equivalent trunk capacity, the X-37B has two angled tail fins rather than a single vertical stabilizer. It is 5,000 kilograms in size, about three metres tall, nine metres long and has a wingspan of about 4.5 metres. ...

 

Read more: CBC News - Technology & Science - Top-secret U.S. spacecraft launches

[CraigD]

Have I got it right that the only thing preventing it from reaching Mach 25 without rockets is thermal management?

IMHO, yes.

 

Thermal management – keeping a jet, (or, in a weirder technology domain, a projectile) from melting due to air friction – is to the best of my understand the main engineering challenge preventing non-rocket surface-to-orbit vehicles from being practical. Though there are significant engineering challenges to getting a jet engine to work at transfer-to-orbit speeds (roughly 8000 m/s, in the Mach 26 range), I think the achievements represented by such experimental aircraft as the X-43, a small unmanned scramjet that reache a record-setting nearly Mach 10 in 2004, show that, were the various burning up problems solved, the jet mechanical issues are solvable. Energy density-wise, replacing carried oxidizer and reaction mass with air gives a tremendous advantage which is, I think, generally understated in our present, preliminary times, the advantage being overshadowed by the heat management hurtle.

In which case advanced materials science might still come to its rescue yet?

Maybe.

 

But a material would have to be mind-boggling advanced, I think, to be both very light (low total mass), and able to passively absorb nearly all the heat generate by air friction of a jet-to-orbit vehicle. Even with new, advanced thermal materials, I think such a vehicle would have to an active, heat-shedding system, like nearly all the current designs (eg: the Skylon), I expect following their same fundamental design of piping fuel through the airframe’s hot spots before burning it in the engine. A cunning design can offset the added weight of this plumbing by using the heat to pressurize the fuel, reducing the size or completely replacing complicated and heavy mechanical fuel pumps.

 

An idea for another fundamental kind of cooling system – firmly in the realm of science fiction at present – comes from David Brin’s 1980 novel Sundiver. Though I’ve never seen a technical, in principle validation of the idea – a refrigeration laser - it is that once could use heat to power a laser, cooling the system by emitting a laser beam into space. Were such an idea realized, on might be able to have a vessel capable of withstanding practically any amount of heat from any source – in Brin’s novel, refrigeration lasers allow spacecraft to penetrate and explore the Sun’s chromosphere!

[CraigD]

as long as it doesn't have to carry peeps, the air force has got a new little number up just recently. :shrug:

…

Mystery has swirled as the force has released little information about the aircraft, which is reusable and similar to a small space shuttle.

 

Likened to the size of a sports car with an equivalent trunk capacity, the X-37B has two angled tail fins rather than a single vertical stabilizer. It is 5,000 kilograms in size, about three metres tall, nine metres long and has a wingspan of about 4.5 metres. ...

 

Read more: CBC News - Technology & Science - Top-secret U.S. spacecraft launches

Mystery may have swirled for the CBC reporters who wrote this story, but to my eyes, it looks pretty much like the same Boeing X-37 NASA handed over to the DOD in late 2006, after drop testing it a few times earlier that year. Kudos to the USAF, though, for launching it into orbiting, and best wishes for a successful reentry and landing – though with all the secrecy, who knows how much of this will be reported to the public?

 

Ignoring the size difference, the X-37 brings to mind the 6-passenger Kliper Russia’s Energia company is still promising to launch in 2012, and hopefully replace the venerable Soyuz spacecraft that’s been the manned workhorse of the ISS since people began getting shy of the Space Shuttle in that role due to its blow-up-y problems.

 

Despite the end of the USSR and big government funding of Russian space engineering, Energia continues to produce and develop some wonderful and workable designs. I’m especially enthusiastic about their plans for an spaceflight system consisting of the Kliper, the ISS, the Parom “space tug”, and any number of unmanned lifters.

[CraigD]

If you come to RBEF where the formats are kind and the whole thing more me friendly i can do a post and we can go to my models.

Alas, such an invitation runs afoul one of the site rules we mods and admins are committed to uphold:

The only type of linking (besides porn, pyramid schemes, hateful sites, and spam, of course) that will not be allowed on our site is when members solicit people to leave our site and join a competing service. That's just common sense. We won't allow people to use our site to promote a competing service any more than a brick-and-mortar store would allow his competitor to paste flyers all over his walls.

In short, bring your images and discuss them here. It’s OK to quote from and link to other sites to address ideas you’re discussing in a hypography thread, but not OK to try and move conversations from hypography to other sites. :shrug:

I think i have two or three actual helicopters ...

 

i go look now...

As you may have gathered already, I’m enthusiastic about – one might even say a bit of a sucker for – space helicopter ideas. Despite the downfall of Rotary Rocket and their troubled Roton vehicle design, I think there’s merit to them, and would love to see more armature and professional work on them.

 

Regardless of its ultimate feasibility, Hudson’s space helicopter idea, and how it translated into the Roton prototype aircraft, are, in my experience, widely little understood. In a nutshell, the idea had 3 main features:

• A simple way to get rocket motors to use air for reaction mass, increasing it’s net trip efficiency, and allowing them to be smaller and less powerful than required in a conventional rocket: by mounting them on a helicopter rotor that they spin. This idea was completely abandoned in the Roton design that was eventually built, which, had an actual space-reaching version been built, would have used its helicopter blades only for landing. This is one of the more confusing features of the design target and the actually built and flown test vehicles, as the test vehicle (the ATV) flew at all times lifted by its rotors, and had no main rocket motors, only 2 small rockets to drive the rotor – in short, it tested only the landing mode of the ultimately intended vehicle.
  
• A way to eliminate the heavy, complicated, energy-consuming fuel and oxidizer pumps required in conventional rocket motors, by using the centrifugal force of the column of fuel and oxidizer running to the rocket combustion chambers. In other words, using the entire structure on which the motors are mounted as a giant centrifugal pump. The feature was retained in the Roton design, but rather than 2 motors in the rotor tips, consisted of, at one time in the design, a single large “annular” aerospike engine, at others, 72 or 96 small motors, places on the circumference of the base of the cone shaped body. As the Rotary Rocket company struggled with design problems and financial failure, it ultimately completely abandoned this feature, switching plans to use a single NASA-developed rocket motor.
  
• Landing like a helicopter. Of the 3 main ideas driving the engineering of the Roton, this is the least original, appearing in early helicopter designs, WW2 superweapon plans (the FW Triebflügel, small kit helicopters, and abandoned 1950s Russian manned spacecraft recovery systems designs, and the only feature that was ultimately retained in the Roton’s design, and actually built and test flown.
  

In retrospect, I think Rotary Rockets compromised their original design ideas too much, ultimately weakening the design so much it was an expensive novelty, and their company a case study in a private space venture gone wrong. Their greatest achievement was, arguably, the dubious building and flying without crashing the most difficult to pilot aircraft in history, though the test pilot for the 3 under 30 m (100 feet) altitude, under 1500 m (1 mile) distance flights is to be much lauded for having not crashed.

[Turtle]

Mystery may have swirled for the CBC reporters who wrote this story, but to my eyes, it looks pretty much like the same Boeing X-37 NASA handed over to the DOD in late 2006, after drop testing it a few times earlier that year. Kudos to the USAF, though, for launching it into orbiting, and best wishes for a successful reentry and landing – though with all the secrecy, who knows how much of this will be reported to the public?

 

yeah; i did read another article about nasa having the bird first. i think the "mystery" is about what they intend to load up in that puppy. :dog: i have heard laser to kill satellites bandied about. :) :eek: :hyper:

 

China Military Report: Chinese cracked X-37B aircraft secret to kill U.S. space fighter!

Beijing at 7:52 on the 23 April, namely: the United States Eastern time at 7:52 p.m. on the 22 April, the United States developed the first human space fighter aircraft X-37B successfully launched. "Atlas 5," the implementation of the launching rocket. X-37B during the war, the ability of the enemy spacecraft, satellites and other military operations, including control, capture and destroy enemy spacecraft, on the enemy military reconnaissance.

 

X-37B space plane, space shuttle serving size, only about one-fourth of the United States, about 8.8 m, a wingspan of about 4.6 meters, the take-off weight of more than 5 tons. Experts say, X-37B space plane in 1982, "Columbia" space shuttle explosion space after the launch of the most anticipated one, developed in the past 20 years, the U.S. government has invested hundreds of millions of dollars. Although the X-37B is only a small spacecraft, but the highest U.S. and other military secrets.

 

The fact that the United States in space weaponization, made the most substantive evil, horrible step, the United States to dominate space control with global ambitions, not only did not die in the financial crisis, but has become more expansive. ...

[Moontanman]

Surface to orbit in one reusable stage? Nuclear is the only real option!

[Pyrotex]

Interesting link about the NASP, Pyro.

Have I got it right that the only thing preventing it from reaching Mach 25 without rockets is thermal management? In which case advanced materials science might still come to its rescue yet?...

No, that's not the full picture.

 

NASP's problems were multiple: rocket equations, mass, strength, thermal1, thermal2 & safety.

 

The rocket equations are the range of brutally high mountains you must climb. If you cannot climb them (metaphorically speaking) then you are not designing a workable rocket system, you are just sketching doodles in the sand. All the thought experiments in the world will not yield a cheap way to orbit, unless they rigidly conform to the rocket equations. They tell you how much energy you will need, the rate at which that energy must be expended, the speed that you can expect and how much speed you will need. There are single-stage-to-orbit (SSTO) equations and MSTO equations.

 

The rocket equations are dominated by mass. The rocket must be light, as light as you can make it. Given the very best metallurgy and aerospace architecture we could assemble in 1990, the NASP (actually, the ideal perfect NASP) still required so much mass that only 1% of the total mass could be payload! You wanna take 10 tons to orbit (a very modest amount)? Then the NASP, fully loaded with fuel had to be 1,000 tons!

 

You can reduce mass, but then you face the problem of strength. Ugly old 1970s rockets are more efficient than the NASP because they punch straight up out of the atmosphere into vacuum as fast as possible. The NASP has to plow through the atmosphere at higher and higher speeds (mach 15 and higher). The NASP had to be strong. Very strong! Hull pressures of several 100 pounds per sq inch! You wanna use scramjets? Then you gotta have a strong, heavy hull.

 

Ugly old 1970s rockets burned their fuel up in 7 minutes or less to get to orbit. The NASP had to store liquid hydrogen and oxygen for more than an hour while it crept up to orbital speed. Thermal energy from friction boiled away the fuel before you got to orbit.

 

This thermal energy was staggering. At mach 15+, even in the near vacuum of 200,000 feet, the hull glows at 2,000 F, 3,000 F, 4,000 F... Forget that! No metal is strong enough at those temperatures. Even the Shuttle's passive thermal system (the tiles) would not be enough. So, you HAVE TO HAVE ACTIVE COOLING. One simple idea is to use some of your liquid hydrogen to cool the skin before using it as fuel. Some hydrogen will be lost. The plumbing to pipe the hot hydrogen to the engines will have to sustain pressures of 1,000+ psi. So you need heavy pipes. You cannot get around the physics. Yeah, modern engineering can let you solve problems better than your dad's generation, but it can't make the laws of physics go away.

 

Safety isn't just how not to burn yourself on a hot stove. Safety is the word we use in aerospace to mean, Will it work, and will it work every time? If not, then how often will it fail? If it fails, do we have a backup system? If it fails catastrophically, then is there a way to at least save the crew? Electromechanical systems fail. God says so, so believe it. If they operate in benign environments, they fail only once every million flights (e.g., a DC-3). If they operate in hostile, dangerous, extreme environments, they may fail once every 100 flights (e.g., Space Shuttle), or maybe every 20 flights (e.g., X-15). A NASP that falls apart at 100,000 feet, mach 15, about every tenth flight is worthless.

 

All of these limitations heterodyne off each other.

Remove mass? Margin of strength is reduced too much.

Increase mass? Margin of payload is reduced too much.

Increase thrust? More mass needed.

Run hotter? Hull melts.

Use more fuel for cooling? Tanks have to be larger.

Larger fusillage? More heating at any given speed.

Use ramjets to save on fuel? Spend more time at hotter temperatures.

Need to be safer (more reliable)? Need more backup systems, which means more mass, which means more fuel, ... and you're back to square one.

[CraigD]

The rocket equations are the range of brutally high mountains you must climb. If you cannot climb them (metaphorically speaking) then you are not designing a workable rocket system, you are just sketching doodles in the sand. All the thought experiments in the world will not yield a cheap way to orbit, unless they rigidly conform to the rocket equations. They tell you how much energy you will need, the rate at which that energy must be expended, the speed that you can expect and how much speed you will need. There are single-stage-to-orbit (SSTO) equations and MSTO equations.

A good post as always, Nelson, but I believe you miss a critical point: the rocket equations apply to rockets, not air-breathing jets (or, for that matter propellers, or tethered flocks of hummingbirds tube fed sugar water and electrolytes ;)).

 

The rocket equations are based on the (true by definition) assumption that rockets carry the reaction mass. Most also carry fuel and oxidizer, though this isn’t a requirement – a rocket could accelerate its reaction mass with power from a thermonuclear reactor, mater-antimater annihilation, power projected (“beamed”) from a remote generator, etc. What distinguishes a rocket from an air propeller driven craft (which include propeller, jet, and tethered humming bird driven ones) is that the latter doesn’t carry its reaction mass, but gets it from the air through which it moves.

 

More than anything else, this is the design attraction of proposed “air breathing” “space planes”. Whereas a rocket must, by definition, carry reaction mass, and is thus constrained by the rocket equations, a space jet, space helicopter, etc, is not. If it’s powered by a very high energy density “fuel”, or beamed power, it’s mass ratio can approach 1, though unless it has some exotic works-in-vacuum propulsion system, such as tether propulsion, it’ll need rockets to circularize its orbit (depending on the specific trajectory, for a typical 200 km low Earth orbit, this requires a [imath]\Delta[/imath]v of 30 to 60 m/s) to avoid reentering the atmosphere before completing a single orbit.

 

The “free” reaction mass that an makes an air propeller driven craft attractive is what makes it unattractive, due to air friction both increasing its total energy requirement, and the much-discussed heat problem.

 

Other than the few simple transfer orbit calculation to find the 30 to 60 m/s [imath]\Delta[/imath]v I mention above, I’ve not done any yet for a non-rocket surface-to-orbit craft, such as for the mass ratio for typical fuels and propellers (turbo and scramjets, and just for fun, a space helicopter, even if its material requirements are implausible). I expect my results will agree at least roughly with those listed for old professional proposals like the Skylon’s, around 5.5, vs. the space shuttle’s 15.4, or a typical jet airliner’s 2.