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Archive for the ‘Suborbital’ Category

62 mile club has a writeup of a beta “customer qualification program” for XCOR’s Lynx suborbital craft. This highlights the differences and current state of play. Rocketships will not be as safe as airliners in the near future, and they don’t need to be. There are millions of things that are less safe than airliners – scuba diving, ballooning, general aviation, motorcycling, probably even driving a car. And yet people do those things because they have the judgement and can decide for themselves.

The key difference is an informed consent. The suborbital rocket traveler should be told of the risks truthfully so that they can decide for themselves if they want to do it or not. This, I gather, has always been XCOR’s principle.

Airlines are not directed at such customers because they are a mass means of travel – the customer is not briefed specially but is expecting reasonably good safety – and there are thus governmental and intergovernmental bodies regulating the airlines and trying to constantly improve safety.

It would not make the slightest sense to regulate suborbital passenger rockets at this time at airline level – there are only a few passengers and the companies should have the time and resources to screen and brief them very well on what it will be like and what the risks are. (This is a must though – you shouldn’t advertise the service as something as safe as airlines.)

There should be some very simple regulation of rocketships regarding the risk to the uninvolved public of course – most companies deal with this adequately by just flying from remote enough locations. And of course there’s environmental regulation – it’s not cool to put tonnes of methanol into the ground water for example. Yet these are small no brainer issues (I’ve heard stories of over-eager environmental protection agencies though).

Nontoxic (or those that quickly decompose to such in nature) fuels and oxidizers should help a lot in this regard. Suborbital rocketry is not that performance critical anyway – it is a great way to find the lowest investment and operating cost approaches to rocketry – and these drive towards “nice” systems. Safe, easy, nontoxic, nonhazardous, redundant.

Regeneratively cooled LOX-ethanol or LOX-methane engines could be good in this regard – propellant spills and dumps are not that horrible to the environment or to the public, and the engine could in theory run indefinitely without any parts replaced if it is just refuelled.

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By ATK in 2005. Shows how little I know.

EDIT: Spaceref had the details, Mach 5.5.

(Scramjets are still not a space application.)

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Ongoing.

Norm AugustineNorm Augustine

You can stream NASA TV with VLC, just paste this link into it:

http://www.nasa.gov/55644main_NASATV_Windows.asx

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And partly what this blog is about (I realized in the middle that I’m typing like in a slide show, so I changed it into bullet points, as it’s an overview and not a deep text). I present my vision that should be aimed for:

What should NASA do?

  • In the near term, NASA should change to EELV:s (Atlas V, Delta 4) and COTS (Falcon 9, Taurus 2) as launchers for the ISS and lunar programs.
  • At the same time, NASA should do basic research and cheap small tech demonstrators for space technologies that give more for less.
  • This should move humanity closer towards spacefaring.

Spacefaring? Spacefaring is making space operations routine.

  • Space faring requires that space access is cheap, reliable and hassle free.
  • Launch is only part of the spacefaring,
  • But only from that point on can the better in-space technologies (tethers, ballutes, sails, ISRU, slings, whatnot) be developed.
  • Hence launch improvements are absolutely crucial for spacefaring

How can cheap and reliable space access be reached? There must be:

  • Many independent providers of space access.
  • It is done largely with well reusable vehicles.
  • The architecture – more of a market – is multi-faceted and the launchers can be improved, new ones can enter the market and old ones can be scrapped

This coal can be reached, in the next few decades.

Things to avoid:

Technically unrealistic choices at the highest level:

  • In the NASP program, the early performance numbers were fudged and there were unacceptable internal politics meaning no real independent technical criticism would be heard at the top
  • In the “Safe Simple Soon” Ares rockets vs the already flown EELV:s debacle, OMB has lacked the expertise to keep NASA on a leash so they are a “loose cannon” controlled too much by the whims of a leadership that fires all who disagree
  • Countless other examples…

Program mentality:

  • Apollo was ended since it was just a short unsustainable program with a specific stunt style goal, not fitting in any overarching smart picture as a sustained capability
  • STS has been an unimprovable yet critical massive monolith, barely sustainable, for various reasons
  • Danger of having yet another single solution launcher (or two) just for a definite program

Lack of motivation:

  • Has NASA become too big and corrupt by internal politics to really do technical or economic choices? Has it just become pure politics and internal struggles for personal or group benefits? (ESMD) There are great and talented people working there, but does it make a difference?
  • What does the whole agency exist for anymore anyway? Or its current lunar program? Is it just a relic from Apollo?
  • How much actually flying a few people to space every year conflicts and directs efforts away from the goal of reaching real spacefaring?

Summarized, NASA’s goal should be a spacefaring humanity in the future, not having a narrow minded program after another.

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You read it first here!

In the sixties, with the cold war at its tightest and the threat of Soviet Union the greatest, Urho Kekkonen, then president of Finland, with inside info about the coming world politics problems, ordered a crash program of massive air defence developments. That included very long range very fast missiles. Since the project was secret and Finland had to remain neutral, no help from either superpower or their allies could be used. Sweden as another neutral country officially declined as well. The country was left with indigenous means.

But the Finnish industry had basically been force-built when the war reparations had to be paid to the Soviet Union, and the after the war born large age groups had just completed education and were itching to get their hands on challenging projects, the nation was ready for a wide variety of new developments – rocketry among them.

The first test rockets were built in the beginning of the sixties in Helsinki and used solid propellants. The first test runs were run just outside Helsinki in a gravel pit, but mostly they were not satisfactory, with explosions and bad performance (it was commented later by the experts that the propellant was too soft and also was IR transparent so ignition was not constrained to the surface). No names are known to have been assigned to these early tests.

A bit later Finland managed to get an undercover German rocketry expert from Brazil, a former Peenemünde engineer whose name was so secret that to this day it has not been uncovered, and with his help the switch was made to liquid propellants. The liquid propellants required more complexity but offered higher exhaust velocity (and mass ratio with pumps), which made individual missiles more expensive but the total amount needed less, as the area covered was larger. (Missile size was limited by the carrying Sisu truck.) The propellants were nitric acid and methanol (ethanol was avoided since people would have gotten drunk on it anyway). Since Finland had no aluminium production capability, highly chosen, prime quality, well tested and processed wood was used instead for the fuselage and aero surfaces. The engine was quite small, and it produced only about 5 kN of thrust. The combustion chamber was made of steel. Only one picture of the hardware has survived, one shot of the regeneratively cooled combustion chamber:

mottis

Due to the lack of time to develop larger engines, several of these small engines were planned for the booster, and one for the sustainer / maneuver stage. It is unknown if there were any flight tests.

Anyway, the crisis passed, and development was canceled. It is rumored that the foreign expert left the country.

Decades passed, and in the late seventies / early eighties, a certain successful unnamed (I have promised to keep it secret) heavy industrial company got interested in the technology and hired the old experts again (and again in secret, this time for company competetive reasons), now aiming for commercial satellite launch and European co-operation (since Finland didn’t have much IT technology back then, it was felt that the western Europeans would build the payloads). Large test launch facilities were built in desolate central Lapland at the army artillery and missile proving grounds. But after only two low suborbital test launches (both successful), it was decided that the industry was too politically hazardous – Finland’s joining of the European economic co-operation agreements required that they do not compete in the space sector, and everything was wiped under the rug again. The lox – kerosene engines were big full flow staged combustion ones in the roughly Thor class, 1000 kN,  and were designed with indefinite reusability and high efficiency in mind with the company’s world top class process and chemical industry knowledge (though they were heavy, since aerospace engineering knowledge in Finland was close to nil). The team developed even new metal alloys to solve the high temperature problems.  Recovery of the first stage would have been by parachute, and the second stage was expendable. The guidance and navigation unit, called “Sirpa” was developed by contract by the state owned telecommunication corporation, Televa, based on technology from the digital telephone switching center developed slightly earlier.

Only one picture of a test survives, this is a piece of film from an instrumentation camera, with the upper half viewing the outside and the lower half having some instrument readings (that are not shown):

ilmasta

You can see some lakes and green so the test was probably done late in the summer, which means this is the second stage test (the first stage test was done in early spring). The first stage carried the peculiar codename “Kuravesi” (muddy water), which probably comes from the muddy test grounds in Lapland when the very long continuous test runs (a 24 hour continuous test run was attempted but had to be stopped 5 minutes from completion, since a reindeer flock was in danger of wandering in the path of the exhaust flames – their destruction would certainly have given up the existence of the program in the press) that melted the ground frost from a large area. The recovery scheme was named “Silli” (Herring) regarding the fisking out operation – the Finnjet turbine powered fast ferry was actually designed for this capability, having a huge roomy cargo deck with large rear doors. No other names from the very secret program remain. Today the technology is forgotten, and my source said that “if anybody wanted to replicate our work now, it would take as long as then, if not longer, again”.

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With some caveats. 🙂 Let’s assume a rocket is launched, and accelerates to constant speed v_c. Then it stays cruising at this speed and at a constant altitude. Landing is disregarded.

The cruise

We must modify the rocket equation slightly for the cruise: \frac{-dm}{dt} v_{ex} = F = \frac{gm(t)}{L/D} dm/dt is mass flow, v_ex is effective exhaust velocity, F is the thrust, g is the gravitational acceleration 9.81 m/s^2, m(t) is the mass as function of time, L/D is the lift to drag ratio. If we use the \Delta t = x/v_c for time, (x is the cruise distance) we can integrate it from start to final mass just like the rocket equation and get the cruise mass ratio: R_{mc} = e^{\frac{xg}{v_c v_{ex}L/D}} Notice how with increasing cruise speed, the required mass ratio for cruise is lessened. This is because less time is spent in the air and thus the gravity losses are lessened.

The acceleration

But we have to take into account the acceleration to cruise speed as well, which requires some mass ratio as well. R_{ma} = e^{\frac{v_c}{v_{ex}}} We don’t take into account the distance traveled during acceleration, or lift, as the acceleration is a relatively short time and distance phenomenon with rockets that easily optimize to have high T/W.

Total effect

Now, for the total required mass ratio, we multiply the two mass ratios. Then we search for the minimum total mass ratio by derivating it and searching for the zero point. We get: v_c = \sqrt{\frac{xg}{L/D}}the optimum cruise speed (smallest mass ratio) Notice how the exhaust velocity cancels out, the optimal speed doesn’t depend on it.

More considerations

If I calculated right, for a 6000 km transatlantic rocket powered flight with a lift to drag of 7, the best cruise speed for minimum mass ratio is 3 km/s. If you go slower, you waste fuel by hanging in the air, if you go faster, you waste fuel by accelerating too much. I think that’s about Mach 9 at some altitude. This didn’t take into account the deceleration: faster cruise speed takes some advantage there! Even if you shut the engine, it glides further. In real life there are multiple issues:

  • acceleration takes time and distance too
  • engine T/W size has an effect as well
  • there is varying mass during flight .which reduces lift needs with time o which in turn effects L/D as you go higher or reduce AoA .which also requires throttling
  • And a million other things.

Also L/D 7 is probably much too good. Oh, and in the transatlantic case, mass ratio required with exhaust velocity 3 km/s would be 7.

Admission of incompleteness

To be more complete, Ian Woollard already posted musings on Arocket how this boost-cruise is really quite inefficient from an overviewing energy viewpoint: it would be best to burn the rocket fuel at the fastest possible speed – that means right at the start.  Then you use the speed and altitude reserve to glide to the goal. To really have a better look at all the problems with this (like really with boost-cruise too), one would need some hypersonic polars of some real vehicle shapes – which cL and L/D at which altitude and speed and AoA.  The boost-glide could have problems as well, if the velocity is very sharply downwards (as you can’t accelerate fast in the atmosphere for fear of melting) and you need a high cL to turn it around to horizontal. And you also experience high g lateral forces there – at 3 km/s or approximately Mach 9, a 40 km radius turn requires 23 gees of centripetal acceleration. Ouch!

Remember kids, this was just a quick post, nothing serious – don’t try hypersonic rocket cruise at home!

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Nice video explanation of the SABRE engine by Richard Varvill.

In a sense, it boils down to the problem of changing the hot fast low pressure intake air flow to a cold slow high pressure flow.

In the Sabre engine, techniques somewhat similar to liquid air plants are used: there is a compressor, that is coupled to an expander, the expander runs from the “waste” heat of the compressor. This is efficient, but it is heavy. In Sabre the compressor is the shock cone (the jet engine style compressor only compresses the cooled air).

The heat exchangers are critical, and I wonder how reliable and expensive they will get with the vast temperature envelopes, ice and thin wall problems of the huge number of tubes there are. On the other hand, such heat exchangers could have uses in many other places as well. (Power generation.) The helium in the tubes is especially leak prone.

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Spacetransportnews has a link to another in the long list of nontechnical space dreams.

Earth’s radius is about 7000 km. The Van Allen belts start somewhat above 500 km from Earth’s surface. Hence, ballistic arcs have to be either very short or then very shallow. And shallow arcs mean high speed. Close to orbital. New York to Paris is about 6000 km. That’s roughly one seventh of the great circle. It is very clear that to travel such a distance ballistically and at low altitude, you need most of orbital velocity. ICBM:s have very high apogees because of this.

The corridor between the atmosphere’s top and the Van Allen belts is so narrow, just a couple hundred kilometers, compared to the horizontal distances, a couple thousand kilometers, that ballistic point to point travel for humans does not make sense.

Nobody seems to recognize this fact. We get vague dreamy projections by even the normally technically hard nosed engineer people in the alt space circles. Wake up. Orbital mechanics wins. Transatlantic point to point is harder than orbital.  Never mind transpacific.

Grumpy mode off…

Word coin: Narrow suborbital ballistic corridor.

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Unreasonable Rocket

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I’m quite that just right now. It will pass. Perhaps.

There’s been some discussion in various places about both NASA and potential future launch vehicles. Everything’s just so static in a large sense. Completely hopeless. I’ll throw in the towel for now.

Almost nobody has the required long attention span or patience to make any useful progress on the space front, and certainly not society itself.

The Players

USA is the only instance that is putting any significant money into doing anything new. And that’s wasted on the Ares rockets. ESA consists of a bunch of bickering countries, they’ve achieved some nice things but most of the people in the parttaking countries don’t even know they exist. No significant money spent on doing anything new, and what is done in Europe, is very often just me-too copying of American approaches. (Take Hermes as an example.) India is running with some crazy hypersonic stuff. China is doing intermittent Soyuz copy PR flights. Japan is doing something overcomplicated and abortive like they have always seemed to.

What are we left with? A bunch of US newspace companies with so little funding they won’t reach much in the next decade (Euro real newspace like SPL has zero funding at the moment). Scaled’s Spaceshiptwo is a dead end propulsion wise with the hybrids, and the air launching provides some scalability problems too. Maybe XCOR’s Lynx will fly some tourists to some altitude, and maybe there might be some X-racers. It won’t change stuff radically. The X-15 lessons were tossed to the trashbin too, to make way for the farces of NASP and X-33. Armadillo might fly something newish. So what? They don’t have enough money to even put turbopumps on the vehicle, resulting in ridiculous performance for orbital missions.

SpaceX? Forget it. It’s a rerun of Orbital Sciences Corporation, at best (and at the moment it looks much worse). No revolution, and evolution only very slightly.

COTS? Maybe something will actually fly, as it seems it has to try to pick up the mess that NASA put itself in with Ares and Orion. I’m not so well versed into the coming phases and how the politics will go. Both Lockmart and Boeing are in Ares/Orion so they don’t have such strong incentives to replace it with their own COTS solution flying on EELV on the short term. Depending how tightly they can keep their own ULA/EELV guys on a leash, and that has been shown to be ugly, people having gotten into trouble for what they have said on some web forums. NASA’s logical short term COTS alternative, a capsule on an EELV is thus self-censored.

But all this, even when happening in a good way, won’t change price to orbit significantly or enable real spacefaring.

What You’d Need

You’d need a refuel and go again reusable launch vehicle (RAGA RLV) that has turbopumps. No newspace company has money for that (and they are wisely using their little money on something else anyway). Besides, you’d in any case need multiple X-vehicles to develop the techniques like TPS or launch infrastructure and procedures to maturity so they could be operated with reasonable crew size and consistency. A launcher could be depended upon.

Human societies don’t seem to have capability to demand long term commitment to that technology development.

Environment Analogy

Same with the environment. If oil prices stay above 100 dollars, coal based petroleum will come soon and the synthesis already will produce massive amounts of CO2. New coal plants will be built too to produce cheap electricity to consumers who want it. Earth will change significantly with the resulting temperature rise.

No significant new energy producing or saving technology or international pacts will be seriously considered, never mind put into effect in the next ten years.

P.S. This post was written with the new Firefox 3. Hope it doesn’t muck up during publishing. Happy Midsummer. Looks to be rainy here.

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