Daily Archives: September 17, 2021

[2021 kcdc] space flight in the 2020s

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This post is my live blog from KCDC. For more, see the 2021 KCDC live blog TOC

Speaker: Richard Campbell

Twitter: @richcampbell

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Notes

  • Talked about the billionaires going to space vanity projects
  • Can do freefall for less money
  • New Sheppard went off path and ignored request to go back on track

SpaceX

  • Will launch majority of commercial payloads this year.
  • Drives down price be recovering a stage
  • New contracts incentives traveling often

Future

  • Blue Origin working on Blue Glenn – longer rocket. Nobody has seen anything yet. Like a bigger version of Falcon. But a big jump from New Sheppard.
  • SLS (Space Launch System) attempts to make a rocket out of other parts. Might fly this year. Targets the moon. Congress keeps paying for.
  • Starship (from Elon Musk). Pieces of it exists. Does R&D in public with youtube watching. Bigger than Saturn V, but both stages recoverable

Reuse

  • In an airplane, 60% is airplane. In spaceship, only 2%. Most is payload and fuel.
  • That’s why it hasn’t been as bad to “fly it once and throw away the airplane”
  • If Starship is successful, reduces cost because fully reusable. Paying for fuel and maintenance. But speculative because doesn’t exist yet. If can do it, costs about the same as a first class airline ticket to go to space.

Space Station

  • ISS (international space station) – mismatch of things. Old. Will end sometime in our lifetime. Originally planned to end in 2020. Now proposals through 2030.
  • Bigalow Aerospace working on inflatable materials to create durable materials and assemble in space. Can connect modules together to build a space station. Three modules would be larger in volume than ISS. Proposed replacing oldest module (Russian one) with inflatable one.
  • Axiom – group of former space station technicians that want to build own space station. Have contract with NASA to build tourism attachments to ISS. Need more money, but raising more.

Moon

  • Apollo was a military mission (competition between US and Soviet Union)
  • Were supposed to be 20 missions but cancelled because dangerous
  • Sent one geologist on Apollo 17 (rest military)
  • NASA wants to build an autonomous space station in orbit around the moon.
  • Can’t leave pieces of the craft each time land.
  • Can’t kneel in a space shoot
  • All solutions require some assembly in orbit
  • Margin of error for landings on the moon is 1km.
  • Moon gravity is irregular – up to 2% distortion. (an inch a second faster or slower.) Think based on craters/impact

Problem in space

  • Fluid builds in face because no gravity. Need glasses even if perfect vision because eye shape changes
  • Get weak even if exercise
  • Bottom of feet hurt from lack of use
  • Need centrifuge
  • Need giant centrifuge for 1G because need gravity and feet to be similar so don’t get sick
  • Can do an experiment with extended lower gravity on moon to see what need to travel to Mars
  • Everything to date has been camping trip where bring everything yu need and take everything back with you

My take

This was a fun end to the day! Excellent pictures and stories.

[2021 kcdc] a product approach to tech debt

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This post is my live blog from KCDC. For more, see the 2021 KCDC live blog TOC

Speaker: Jennie Ocken

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I went to another session first so only saw the second half of this talk.

Notes

  • Conway law 
  • Document debt.
  • Decide how much acceptable.
  • Project vs product thinking.
  • Short term thinking.
  • Can deliver quickly if it is less valuable or poor quality. 
  • Three horizons – majority existing market   Next new market if something new for existing market. Then both new 
  • Measure what fire fighting. We reward this culture. Have to thank senior people for working weekend to solve problem. But then juniors think have to. H
  • Hippo. Highest paid persons opinion
  • Objective truth. What are facts. 
  • Debt compounds. 

My take

I missed half, but I liked the half I saw!

[2021 kcdc] Algebraic in Java: Pattern Matching

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This post is my live blog from KCDC. For more, see the 2021 KCDC live blog TOC

Speaker: Chandra Guntur

Twitter: @cguntur

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Background

  • This is part two of a talk. Part 1 covered algebraic types (ex: enums). Don’t need to have seen it for this talk
  • Pattern matching came froM SNOBOL (string oriented and symbolic language) in 1960s
  • This presentation is in https://github.com/c-guntur/algebraic-in-java

Switch case pattern matching

  • case can be type of object. ex: case Integer i -> “int”
  • Must put “case null” in order to avoid a null pointer
  • Guarded expressions: case Integer i && i < 50
  • Can use same pattern variable name across case statements
  • Flow scoping

If statement pattern matching

Deconstructing is from JDK 18 preview – https://openjdk.java.net/jeps/405 (preview features can change)

  • if (o instanceof Point p)
  • if (o instanceof Point(int x, int y) – deconstruct value. Implicitly type safe because null won’t reach branch (null instanceof X is always false)
  • if (r instanceOf Rect(Point(var x, var y), var lr) – nested deconstruction
  • If have varargs, can match by coordinates/number of elements. Ex Point() matches no params, Point(var a) matches one, Point(var a, …) matches one or more
  • For array, if (o instanceof String[] { String s1, … } – one or more elements in array

Pattern matching isn’t new

  • Always had instanceof
  • Visitor pattern
  • Regular expressions

My take

I’m excited Java is going to be adding a lot of this. The format of presenting from inside IntelliJ is interesting. The presentation was short though. Only half an hour. I liked the answer to my question about scope – pretend there is an else block!