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Long USAF hypersonics history. Lesson: reusable aircraf-like access to space is not a new idea.

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Venture capitalists shy away from reusables because they don't have the billions. Doesn't take billions, it takes a smart design.

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Many rocketplanes, 1960-2000. Lesson: vertical takeoff & landing is simpler & easier to do.

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Lot of bias toward horizontal take-off & landing. It can work, but VTOL is a lot easier to do.

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National aero-space plane program. Lesson: $3B spent between 1986 and 1994 - biases can be expensive. Active cooling, complex airframe integration, need a lot more total delta-V because of drag. Low propellant density because LH2 is 4.4lbm/ft^3 - grows the aiframe. Active cooling of the surface over 40% of the surface area. (Ed: this was a challenge with the SR-71 & Valkyrie as well).

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HAVE REGION rocketplanes in the 1980s. Lesson: USAF bias was vertical takeoff & horizontal landing. Used rocket sleds to get off the ground. Used SSMEs & a 1970s structure, with titanium, superalloys, and a few composites. Integral tanks: Mechanical, pressure, thermal loads.

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Rocketplane metallic structures were fabricated. Lesson: successfully tested, albeit durability concerns persisted. (From the slide)

Fast forward to 2019: SpaceX approach, BFR Steel-300 airframe with active cooling.

NASP program was developing advanced composites, but there are some thermal advantages to metallics. Can SpaceX find a balance point to fly with something heavy like steel and make it work?

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Why in the world isn't the US government out in front and trying to put these cutting edge technology in the pockets of entrepreneurs?

Slide: Single stage rocket technology studies, circa 1991. Lesson: two-stage or not to stage - both can work with pros & cons.

Still like aerospike rockets (ed: efficient at a much wider range of altitudes, attractive for SSTO), but they have issues.

Single stage costs a lot more, smaller payloads, but current commercial market has small payloads right now.

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Recurring cost projections from the 80s & 90s. Lesson: consitent projection of flight costs below $300/lb & $3M/flight.

HAVE REGION in the 90s built & tested SSTO structures, SSTO project built DC-X in 90s.

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Airbreathing - high Isp but with challenges. (went through slide very fast)

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High Isp essential for hypersonic cruise, but NOT space access.

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DC-X "ops lab" - flight tested from 1993-1996. Lesson: cheaper, faster, better possible, but hard for government contracing.

DC-X/XA demonstrated:
* Streamlined management
* Aircraft-like O&M
Total ops team was 25-35 people
Small crews of 6-12 people
* Aircraft-like flight ops
- Excellent crosswind & adverse weather landing capability
NASP & HAVE REGION matured lightweight structures in parallel
Todays commercial marketplace traces its heritage to DC-X (bottom text cut off)

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DC-X was a complete system, more than a vehicles. Lesson: infrastructure need not cost billions

Vertical take off and landing. Lesson: many key advantages.

In my opinion, it's a much better solution.

Key advantages:
* Incremental flight tests
* Powered landing
* Few facilities
* Minimal real estate
* Adverse weather flight
* Flexible abort envelopes
* Minimal dry weight & development cost
* Altitude compensating nozzle option

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DOD technology & flight tests paved the way. NASA "x-planes" in the 90s, the "billionaires" in the 2000s. Many hypersonic children.

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Many space access concepts studied. Lesson: Two stage or not to stage? Rocket or airbreathing?

Slide shows RAM & SCRAM concepts along with rocket concepts. Most of the rocket concepts are two stage and thus much smaller.

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What has changed? Rocket plane technology readiness level is high - TRL 6+.

Past programs over-spec'd requirements (SSTO, scramjets, heavy lift, crewed, etc) and used immature technologies.

XSP demonstrated 10 flight duration engine ground tests in 10 days.

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We're up to the point where the private sector has jumped in and a lot of people are chasing launch systems.

Can't argue with the success Elon has had. Designed for full reusability from the get-go. My concern with Blue Origin & SpaceX is that they've sucked up a lot of the energy of the VC & entrepreneurial world, and I'm convinced you can do this with a lot less money.

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DARPA: What is Phantom Express? Reusable hypersonic first stage, expendable upper stage

Goals: Fly 10x in 10 days, no upper stage/payload
...

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Key technologies. Lesson: Composite structures and ceramic TPS are mature. Large scale structures, Complex structures, Polyimides, panel structures.

Shtructure weight: shuttle era vs now, we're 30-50% lighter now.

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Composite cryogenic tanks are mature. (Pronounced "Big Falcon Rocket" in a way that was almost indistinguishable from "Big Fuckin' Rocket"), called Starship now.

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Optimized composite solutions must be designed in. Lower cost - higher for design but lower net. Why? Affordable comopsites. Smart design - 10x fewer parts.

...

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Pump fed rockets once the province of BIG government. Not anymore. Lots of big rockets, >100k lbf thrust, and little rockets, 5-35k lbf thrust.

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Hypersonic airbreathing & rocket technologies overlap - a lot!

If I had my druthers I'd like to see a program that pushes component technologies and makes them available to industry, just like <something> in the '60s.

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Predicting the future disclaimer. Lesson: beware of the "experts". Lots of examples of "experts" being wrong about where the technolgiies will go. "Man will not fly for 50 years" in ~1900.

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Maturing now: reusable first stage. Mach 4-12 reusable first stage enables access to space & global reach.

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Coming soon: fully reusable space access. Enables global reach aircraft. SR-71 CONOPS offers analogy for fully reusable global reach CONOPS. Survivable in A2/AD environment. Hard to kill with once around missions. Deploy/reconstitute when & where needed. Deters use of ASATs against US sats.

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Starship is an example of fully reusable. Akin to deltaclipper circa 1996 only much bigger. Resolves key issues: simple cylindrical shape is easy to build. Fins/canards for yaw control, high alpha flight, etc.

Aircraft-like fully reusable access to space, which is where Elon wants to go. Point-to-point transport. Payload is huge. 747 sized.

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What will be the cost of a ticket to space?

Ticket price to orbit $101. (bunch of text in the middle of the slide eaten by keynote) "Assuming we can work out a few engineering details.

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Flight rate critical. Cost still 100x the cost of electricity (what he used to compute the ticket price to space at extremely high rates). There is room for improvement!

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Aircraft-like ops enables military spaceplane(s) and global-reach aircraft.

(Ed: I only care about this because it's a way to get government to fund research_

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Boost glide P2P transport is a leapfrog approach. Got a 7,000 mile range, almost global reach. Not going all the way to orbit, never going to zero G. 50% of people get sick. Out-of-shape guys like me actually do better in zero-g.

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Giant slide fully of "a few key lessons". Not going through the whole list, just a summary of previous slides so already mostly written up.

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Management lessons learned. (Full transcription of slide)
* Agree to clearly defined program objectives in advance
* Single manager under one agency
* Small government and contractor program offices
* Build competitive hardware, not paper
* Focus on key demonstrations, not everything
* Streamlined documentation and reviews
* Contractor integrates and tests prototype
* Develop minimum realistic funding profiles
* Track cost/schedule in realtime
* Mutual trust essential

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So often get into this situation where government and the contractor are adversaries. Bad, bad mistake.

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A few lessons from DC-X
* Fast track, rapid prototyping can be done by govt, but it's not easy
* Precise vertical landing possible, differential GPS allows landing on launch stand
* Blended differential throttling with engine gimballing, elimination of all hydraulic gimbals should be next goal?
* Engine out abort during flight, potential for aircraft-like reliability
* VTOL can land on cement, grated trench, unprepared and "prepared" gypsum.
* Hydrogen insidious, leaks, but can be managed safely

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* Employed Matrix X to autonomously generate flight software at ~10x lower cost
* Low cost, minimal and transportable infrastructure designed for both ground and flight test

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BIG DC-X lesson learned: Government start/stop investments damage the industry. Be consistent.

Build X-Planes, not systems
Take incremental steps
Build on successes (don't keep starting over from scratch)

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Final thought: just do it!

From October 9th, 1903 edition of the NYT: "flying machine might be evolved by the combined and continuous efforts of mathematicians for 1 million to ten million years."

SAME DAY, from the journal of one of the Wrights: "We have started assembly."

Question about oxidizers & composites.

A: LOX can cause fires, but there are ways to use it safely. Some interesting storable propellants that might provide an alternative to LOX.

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Question from Dave Weinshenker about reusables vs just trying to drive manufacturing costs down. "Tin can like" vs "aircraft like".

A: Room for both, reusable is better for reliability.

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