Posts by John Smith 19

@Stuart Duel

3 Things.

BAU. Business-As-Usual. 1000 page "procurement" contracts with *lots* of prescriptive clauses (we don't just *want* this done, we want it done *this* way), pre-design-reviews, Preliminary Design Reviews, Critical Design Reviews, change control.

Cost plus contract, *despite* the fact that basically what it comes down to is "Give us a Saturn V lifting capability to LEO" which has been done once successfully already (and at least one *complete* example exists to study, mostly on the law out front of various NASA buildings). I like to think of these as more cost++.

It'll be executed by "Big Aerospace" who will probably set up a whole "Division" to do this (which of course will need a VP or two to oversee matters and make sure that fat budget is "properly" spent).

The proper example to study would be the DC-X programme of the early 90's under Jess Sponable, whose airframe was *also* built by Scaled Composites (BTW Scaled is actually part of Northrop Grumman, who seem to be smart enough to leave them well alone most of the time).

DC-X. 0-M3. 4x RL-10 Hydrogen/Oxygen powered rockets, uncrewed built for the SDIO.

Price 60m.

It's amazing what you can do when your organizations goals have *nothing* to do with *how* something is achieved, they simply want to get it *done*.

@A J Stiles

"Crew" would be the gender neutral term but this process has been around for a *long* time.

It dates from the days of the "Mercury 7" (or rather Mercury 13 until NASA got cold feet at the prospect of smallish chunks of American womenhood falling from the sky in a failed launch).

Things might change in another generation or so.

<sigh>

@Mike Brown

The commonly suggested proposal is to return to its roots as the NACA, providing impartial R&D to *all* players in the US aircraft industry. What might be called pre-competitive research. Not priatisation, re-focusing their operations onto core objectives.

This would leave the manned spaceflight centres looking vulnerable. However Marshall does have some unique facilities (but would need a slim down, not something Sen. Dick will tolerate easily) and could offer their services to anyone who wanted mission planning done for complex missions with multiple payloads. JPL would remain in probes and remote sensing (but presumably would not be tied to NASA only launch vehicles).

@Destroy All Monsters

My my, someone has been reading their NASA standard terminology manual.

@Captain thyratron

"Musk knows the same thing Wal-Mart does: If you charge less by the right amount, you can make more money by drawing business away from relatively expensive competitors. "

He's actually making a *bigger* gamble than that.

A key reason why companies charge what they do is their customer analysis says business *only* improves when costs drop by a *lot*

*Not* the 50% that the EELV programme was designed to give NRO/USAF flights.

I'm talking 1000% or to put it a more useful way price has to drop to 1/10 current market levels for the demand to start *steeply* rising.

Musk reckons at 3-4 F9Heavy launches a year he can get that down to $1000/lb, which is something of a magic number in the launch market.

Big risk (although the bookings taken by Virgin Galactic suggest there *are* quite a few people who would want to *go* to orbit, rather than just look at pictures of it).

Big reward.

@Mike Flugennock

"has also made me feel as if I were living in a Stephen Baxter story, which almost too damn' much to handle."

Except in Stephen Baxter's novels NASA manages to *launch* something. Admittedly quite a few of the crew end up dead but they manage to *achieve* a goal.

IRL NASA has managed to avoid killing any crew for quite a while but continued to spend money and not really achieved very much. IIRC $11.4Bn of cash into Constellation got 1 test flight.

@Beachrider

"he NASA budget doesn't have force-of-law,"

Budget no.

*Appropriations* Act. Yes. I believe the clue is in the word "Act," as in Act of Congress.

@Alan Brown

"The only question is..... would you go into space in something built by italian engineers?"

Do you know what a large chunk of OSC's CCDev is based on and where it's made?

@Mike Flugennock

"Stop me if I'm wrong, but wasn't the as-flown STS Orbiter designed by Max Faget -- "

You're wrong.

Like various other NASA projects the same name has been applied to several different vehicles which changed out of all recognition between proposal and implementation.

Faget's *original* shuttle design was for a straight wing low cross range, low wing loading "space truck." with a 20Klb payload pay launched as the 2nd stage of a 2 stage manned vehicle (*both* using the same SSME with different nozzles) and IIRC having jet engines in case they fluffed the landing and had to make another pass.

Faget's plan was to have a descent *so* mild that the wing top surfaces would not even *need* thermal protection.

However his entry maneuver was considered pretty sporty and prone to stall, which made the pilots of the astronaut corp nervous.

And then the merry men of Tricky Dicky's OMB got busy with a few "revisions"...

Not quite what you see when a Shuttle takes off, is it?

@Bronek Kzicki

"I'm still pondering how does this relate to "how they operate", care to enlighten me?"

The question is ambiguous.

On the assumption you mean how the *structure* operates it splits the loads being carried into different types. A more detailed explanation follows.

"airstream" loads are carried by the skin.The skin is currently spec'd as a French ceramic called "Pyrosic" in the updated PDF, and is mostly a Silicon Carbide. Like parts of the SR71 it is corrugated parallel to the direction of airflow. It is joined to the load bearing "ambient" structure by "hairpin" rivets. The skin is c800c hotter than the frame. It can be made airtight (unlike the SR71, whose outer skin served as the wall of the fuel tanks) because the heating is partly re-emitted into the airstream (like the tiles on the shuttle) but also partly absorbed "flattening" out the corrugations on the surface and stretching the hairpin rivets underneath. All should be *poor* thermal conductors.

What you might not realize is although skylon is airtight it is designed to be *vented* (also much like the shuttle, which has 16 motor controlled vents to do so). The air is sucked out by the surrounding air pressure on ascent and *stays* out when the vents close. This eliminates convection, and mounting the skin structure on low conductivity pins stops *most* conduction into the interior while encouraging its re-radiation outward. That leaves thermal radiation.

Radiation is dealt with using multi-layer insuation. This is standard kit on satellites and some launch vehicle stages. The interleaved inorganic mesh layers prevent heat conduction while the metal foils reflect any IR from the back face of the skin back outward to it. It's the lightest known form of insulation *provided* you have a reliable vacuum.

The surfaces of the tanks are coated with a layer of polyurethane foam with an SG of 0.06 to a thickness great enough to prevent water condensation on their outside. This would be far too fragile to coat the outside of say the Shuttle ET but is adequate because it's protected from airflow.

Using *multiple* structures in this way is very different from a conventional vertical takeoff rocket.

"Static" loads (tank weight and engine thrust) are carried by the "truss" frame, sitting inside the MLI layer.

With MLI keeping the heat *out* and polyurethane foam keeping the cold *in* the frame can be made of materials that are strong at *near* room temperature without worrying about their high temperature strength properties..

The frame is made of unidirectional laid carbon fibre tubes fitted into titanium fittings made in 2 halves and "flash" welded together for speed and to retain good materials properties with a very thin heat affected zone. This work was done under an EU grant at IIRC Bristol University some years ago. Note that with modern plastics near room temperature *can* exceed 250c (the maximum use temperature on the Aluminium skin of the shuttle is 183c).

By "floating" the skin away from the tanks and non airstream load bearing structure from day 1 RE aim to side step the pitfalls of the tightly integrated Shuttle structure of stressed skin (distorting under thrust and gravity loads) stressing (or rather over stressing) the brittle ceramic tiles. In principle with the Pyrosic panels floating and thin they should *bend* on minor impacts rather than shatter. While they wouldn't survive being hit with foam of an SG of say 0.2 at M3 they are also not likely to have a *source* foam anywhere near them either.

The 4 tanks are designed to be rigidly mounted at one end and carried in a series of Kevlar "slings" to they are free to grow and shrink under temperature loads without high deformation forces building up. This is not clearly shown in *any* RE diagram.

While the truss structures has never AFAIK been tried in carbon fibre tubes it has a long history in UK airship and bomber design, mostly by Barnes Wallis.

Rivet joined plates remain a common aircraft construction method and the idea of hairpin rivets IIRC was one approach to the design of the X20 Dynasoar, although the material of these plates and the rivets would be viewed as exotic by mainstream aircraft manufacturers.

It *should* also be capable of a high degree of automatic assembly, even if the individual tube insertions and panel riveting were fairly slow.

@JeffyPooh

Funny you should mention that.

I wrote to RE a long while back on that and a few other points.

They kindly wrote back and explained that they *had* considered it and the design is *more* resistant to it than a conventional turbo fan or jet (I point out that's provided you defrost the goose first). They were a *lot* smaller then.

In hindsight it would be a lot like a bird strike on an SR71 nacelle.

Firstly there are 2 engines on each side so worst case would give a 50% loss of thrust balance. Secondly I'd guess the SABRE core site *directly* behind the entry cone. A bird strike would slide down the cone and hit the inlet but by pass the engine core, possibly clobbering part of the "Spill ramjet" (I'd guess they can isolate sections of the feed piping on this) before being flash broiled by the superheated steam on the way to the exit.

Hitting the inlet heat exchanger matrix *would* be a very bad day for all concerned but I *suspect * you'd have to fire the goose at *just* the right entry angle to do so. In these cases I think civil aircraft certification bodies start breaking out probabilistic risk assessments, with the odds (of a mishap) lengthening as the inlet closes on ascent.

99 times out of a 100, SABRE cooks the goose. 1 in a 100 (or rather less), the goose cooks the vehicle.

@Mike Richards

I once worked for a guy for whom English was not a first language.

Imagine a Mysteron who swears a lot.

*Very* unnerving and quite sinister.

@Pete 2

"That's really where the scuttle went wrong (the Soviets managed it, with their Buran: who's one and only flight and landing was handled autonomously"

Part of the *implicit* design criteria were "Must keep astronaut corps fully employed for conceivable future."

At least 1 supplier proposed a 2 stage winged design with the first stage uncrewed (the mother of all RPV's). Marshall stated "No unmanned stages."

Shuttle has *always* had the ability to autoland but required someone on board to throw certain switches (like the ones that drop the landing gear. It cannot be retracted and kills the glide speed. NASA did not want that on direct computer control). There is now a cable that can wire up/bypass all the manual bits as well.

Pilots refuse to engaged auto land stating it's feel is too "different" and they don't think they could get used to the difference in an emergency. Besides which if you'd practiced for 5 years to land the worlds fastest aircraft you'd probably want your shot at it when the time came.

" by the on-board AI)."

Not even necessary. Just carefully worked out logic, much like the autoland function on commercial aircraft.

Bear in mind the Shuttle is unstable. It *cannot* fly without computer intervention and working hydraulics. There is *no* mechanical backup (This is why the landing simulator scenes in the film Space Cowboys are hilarious). Once you're committed to *that* much automation the rest is just more code.

AC@13:38

"I say get the fudge on with it "

You are Fred Goodwin and I claim my free lifetime unlimited overdraft facility at RBS.

@F111F

"Since the thing is mostly fuel tanks fore and aft, it will be interesting to see how they manage to maintain CG (Center of Gravity) as it burns the fuel."

Pretty much the way some of the RE design team solved it on Concorde.

Look at the cutaway diagram.

Each propellant is stored in *two* tanks. 1 in front of the payload bay, 1 behind and note that LO2 is roughly 16x more dense than LH2.

Controlling *which* tank each propellant is drawn from matches most (if not all) of the CG shift.

BTW the design is designed to be statically stable so the control surfaces do not have to flutter about continually like the Shuttle during a landing.

@BristolBatchelor

"Now I thought that the tanks holding liquid O2 on normal rockets could only do so for a short time, as the stuff is nastily corrosive."

No.

Current LO2 and LH2 tanks are loaded with propellants at Normal Boiling Point. It take *very* little heat input to start their contents boiling.

Either the tank pressure starts rising (GO2 is roughly 700x the volume of LO2) fast or the tanks starts venting, dumping a very effective oxidiser into the environment where it could turn any stray spark into a fireball.

RE is planning to operate a Zero Boil Off tanking arrangement (something NASA has repeatedly looked at but not got around to doing. This "Sub cools" both propellants *substantially* increasing the time a Skylon can stay on the runway before taxiing off.

As for "corrosive" LOX is one of the most *common* cryogenic liquids in the world. Every major hospital uses it, along with many steel processing plants, not to mention its routine transport by road tankers and freight cars on railways.

If you were talking about Flourine, NTO or any of the Amines you'd have a point.

They are *very* nasty.

Bronek Kozicki

You might not be aware of this but RE was formed in 1989.

BTW your comment about ablation indicates you have no idea how they operate. RTA or their website.

It's been around for about 20 years.

@laird cummings

"Even it it never gets off the ground, the value of all the primary research and engineering will translate to many other projects. Knowledge of that sort is never wasted."

Actually *most* of the research to get here has *already* been done.

RE's has partnered with *many* companies and universities (both in the UK and the rest of Europe) through its own funds and with EU funding (and *very* occasionally UK govt funding) in some cases to *prove* the various elements.

The *big* costs come from scaling up these lab trials, FEA simulations and prototypes to a *full* size vehicle.

I personally would like to seem them investigate premixed catalytic ignition to eliminate a high temperature/high voltage ignition system but that's not a necessity.

@Andydaws

Proving once again the safest place in Germany to site nuclear reactors is...

The Czech Republic.