32faction

My background is in aerospace and while I’m not an expert on COPVs, I’m familiar with their design. Carbon fiber overwrap is really good for internal pressure applications or in other words, the typical pressure vessel due to carbon fiber’s very high tensile strength. Think of those videos where folks put rubber bands on watermelons to make them explode; the concept is similar to a COPV in that the rubber bands (carbon fiber) “compress” the watermelon (pressure vessel) to “contain” the pressure. COPVs can take high internal pressures of 6000 PSI (which is the same internal pressure of the ISS NORS tank used to recharge oxygen and nitrogen on the ISS and coincidentally is the same *external* pressure experienced at the depths of the Titanic. (Some helium bottles have higher internal pressure). While in aerospace applications there are some load cases where the COPV has an external pressure load on them like a helium bottle stored in a propellant tank on a SpaceX Falcon 9, those pressures are nowhere near deep sea pressures.

The reason why I don’t think COPVs are a good design for an external pressure application is the load direction; carbon fiber tow doesn’t really do well maintaining an external load. Think back to the watermelon example; apply an increased external pressure and the rubber bands really don’t help with withstanding that increased pressure.

Carbon fiber itself is very difficult to verify that you have the correct properties once they're wound onto the tank. The properties are anisotropic meaning depending on the direction of the fiber you’re gonna get different mechanical properties. Defects like delamination (when a wind unwraps) or voids between the tank wall and fiber are common if you don’t have a qualified winding operation and really really good procedures. In short, while not needing software, repeatability in manufacturing a COPV is incredibly difficult. Part of the reason SpaceX switched to metal tanks is that the mechanical properties of stainless actually increase in a cryogenic environment so there’s an added benefit.

In 2016, SpaceX’s Falcon 9 carrying AMOS-6 exploded during a routine static fire due to a buckled liner of a COPV on the 2nd stage LOX tank. The liner buckled which created a void between the liner and the fiber overwrap which then developed solid oxygen (or an ingress of LOX) that initiated an explosion due to friction. Falcon 9 had been flying for 6 years at that point so I’d consider that a pretty mature or at least an “operational” vehicle so for it to explode on the pad like that is how tricky COPVs can be.

EDIT: Spelling and clarification on delamination

We decided against launching them because the laser would have a limited power supply and could only deorbit X amount of debris before completely depleting its power supply; something solar panels can't effectively recharge (well you'd need A LOT of them). Combine that with cost for launch, it gets pretty expensive to deorbit only a few satellites.

Because of this we went with surface based lasers; they could be recharged using the local grid and clean a specific section of the sky. We looked at placing lasers at locations with high altitude and cross referenced them with the local $ per kilowatt hour. Never really got to the stage of deciding where to place one since we were still stuck with figuring out the market for it. I guess someones active satellite needs to get Sandra Bullocked by some old debris before we start going "hey. there's a market for cleanup!".

The ISS is currently looking into a laser system to clean up debris if i remember correctly. I guess if they ever figure out the person who uses it would get to call him/herself "ISS Door Gunner"

and the Kessler Syndrome is NOT helping either

> The Soviets started using it because it would provide good coverage of their very nordic territory

They also used it to surveil/recon the United States as it can loiter in US airspace for a while.

One of my first startup ideas I pitched to YC was to deorbit the inactive LEO satellites/debris as as service utilizing kilowatt-class lasers utilize radiation pressure to degrade the orbit enough to let atmospheric drag take care of the rest.

Well due to (IIRC) the Outer Space Treaty, spacecraft launched is still owned by their original company and I dont think the original company, or anyone else for that matter wants to pay to cleanup their trash, therefore no market.

Didn't get interviewed for most likely that reason.

gif of explosion: http://imgur.com/SYwUIbI

Hey Kevin and Sam,

Pitch: We're ATLAS, we plan to launch extremely small cubesat payloads (x<100kg) into low earth orbit on demand.

1) How much calculations/numbers crunched would we need to convince angels to invest? Rockets of this size aren't something we can bootstrap without a little financial support.

More Background:

Right now, the only way to get a cubesat into orbit is by ridesharing on bigger rockets as a secondary payload. The problem with this is they're not assured to reach a preferred orbit and are at the mercy of the scheduling of the primary payloads. NASA currently has a backlog of ~50 cubesats that need to get into orbit, as well as the many upcoming launches (including SpX this Sunday). We are currently working on the RFP for the Venture Class Launch Service however we may not have the resources to fully complete it by the deadline (13 July). We plan to market this service to Universities as well as hobbyists and government space agencies.

> He urged the Air Force's Space and Missiles Systems Center to "embrace SpaceX innovation and practices," while SpaceX needed to understand the Air Force's need to mitigate risks, and be more open to benefiting from the government's experience.

I found this to be the most important point in the entire article because I'm sure the USAF is very "old guard" with a mentality of "if it isn't broken don't fix it" while on the other hand, SpaceX is the new kid on the block with the newest and coolest tech

Sure, but it was necessary. I'd do it too if it meant my startup would survive.

Will there be info on them coming soon?

I know there was one aerospace startup in W15 but are space startups out of YC's scope?

I did my undergraduate capstone class on the Kessler Syndrome. UNCOPUOS, the United Nations Committee on the Peaceful Uses of Outer Space dictate that a satellite must deorbit itself within 25 years after mission completion.

The Kessler Syndrome right now is a potentially exponential problem that we should be conscientious of because our access to space depends on open orbital lanes.

I want to submit a YC application proposing an orbital debris mitigation as a service company but im not sure if it's an idea YC will facilitate

The science behind the movie Gravity wasn't too accurate but the scenario the characters found themselves in is very very plausible.

PR is a big thing especially with private rockets. On the CRS-1 mission, they referred to the engine anomaly that occured During ascent as a "rapid unscheduled disassembly" when really it was a rupture in the engine fuel dome. Luckily the Falcon has an engine out capability so it still completed its primary mission. Had this been a NASA or other public company like ULA, the vehicle would've been grounded for X amount of months pending investigation, which in the case of SpaceX, would kill it's revenue stream. No launch, no profit.

that's partially why ULA keeps both the ATLAS and Delta family rockets. If one is grounded you have the other to rely on. SpaceX only has the Falcon. Hell, even the Millenium Falcon had problems with its hyperdrive.

Not trying to knock SpaceX here, I'm actually trying to get a job with them in aerospace engineering. They just have both an advantage and disadvantage by having one rocket system.

Id like to know more info about that aerospace startup.

Location: Phoenix, AZ

Remote: No

Willing to relocate: Yes. Anywhere in the world.

Technologies: LabView, CATIA, MATLAB, SIMULINK, ANSYS, Adobe Fireworks

Email: GaliciaL@my.erau.edu

Résumé: Upon request.

LinkedIn: https://www.linkedin.com/profile/view?id=15091975

About Me: Aerospace Engineering student graduating Spring 2015. I'm looking for a position in space or drone startups (SpaceX, Matternet, Makani Power, Airware etc.) Strong CATIA and project management skills. Fast learner, team player. Basic understanding of UI/UX, Learning ROR.

There have been a lot of companies opening up offices in Phoenix, AZ. Specifically Scottsdale. If I remember correctly Weebly and Yelp have offices on Scottsdale Rd. Usually Phoenix is known for it's Real Estate investing but tech companies have been getting more more and more recognition. I think we're calling it Silicon Desert.

I go to school (Embry-Riddle) about 45 minutes drive from Arcosanti and I have to say while I pass the signs for it I haven't been up there. I remember one of my professors mentioning the project during my Alternative Energies class so I thought it was some sort of solar project.

My understanding was Pluto could not be a "planet" because it was not a part of the formation of the original solar system due to it being located beyond the frost line boundary [1] which separates terrestrial planets from gas giants.

Basically, anything within the frost line boundary is close enough to the protosun that things like solid water, CO2, et al. melt, allowing for accretion of solid matter and eventually rocky (terrestrial planets). Anything beyond the frost line, and these solid materials freeze up then accrete, and then collect gas from the protosolar accretion disk, forming gas giants.

It's entirely possible Pluto could've been a part of the original solar system but somehow wasn't massive enough to collect gas, or it was a captured object not present during the formation of the solar system.

Either way, I'm sure New Horizons will discover more.

In my opinion, the IAU was correct in downgrading Pluto to a dwarf planet. Scientific observation and study should not be dictated by social tradition.

[1] http://en.wikipedia.org/wiki/Frost_line_%28astrophysics%29

Definitely convinced me. I figured life jackets on boats are what seatbelts are to cars. It's a small thing you probably should put on.

I think what they were going for is the water can be so cold you loose the sensation in your fingers so trying to get a response combined with decreased body temperature, results in applying too much force to break it off.

Also makes for a good cringe factor to make the simulation feel even more real.

Plane crashes can be over water. Just be sure you grab your seat flotation device to make treading water somewhat easier.

There should be a place for you to click. It seems you have to be on a desktop of iPad for it to work well.

Id think if the US was to look into nuclear based engines we should restart the NERVA program. But of course with anything nuclear politics and environmental activists would be all over it.

My propulsion professor (former deputy director, AFRL Propulsion Directorate) said the way they get around the buzzwords "nucler" and "atomic" was to call it "general purpose"

Some quick facts the article didn't mention about the SR71:

- In order to save gas, the plane actually sped up. This was due to the "turbojet-assisted ramjet" design of the Pratt and Whitney J-58. Ramjets can't operate at slow speed therefore it uses a turbojet design to get it going. Then at high speed, the J-58 transitions from a turbojet to a functional ramjet. You can see the transitions here: [1]

- The SR-71 was actually preceded by the CIA's A-12 OXCART program. The A-12 was slightly smaller, had only 1 pilot and was a bit faster. Since stealth wasn't fully understood yet and wasn't a primary design parameter, the design thinking at the time was centered around either flying high or flying fast to combat the Soviet Union's anti-aircraft systems as well as to intercept bombers. As more and more research went into stealth as well as intercontinental ballistic missiles, the "flying fast" design thinking began to dwindle due to its expensive flight and maintenance costs.

This eventually led to the creation of the United States' nuclear triad: submarines, ICBMs, and strategic bombers: Submarines are the stealthiest of the three and can survive a first strike attack, ICBMs can be launched from a friendly controlled area and are difficult to intercept once launched (especially MIRVs), and strategic bombers such as the B-2 Spirit can be used for a stealthy first or second strike but can be recalled whereas with the other two, once fired there's no calling them back.

- The SR-71 was designed completely using only slide rules and paper. [2]

[1] http://upload.wikimedia.org/wikipedia/commons/8/89/SR71_J58_...

[2] http://www.lockheedmartin.com/us/news/features/2013/sr-72.ht...

Yes. Since SpaceX deals with rockets that can potentially have ICBM capabilities workers need to be US citizens to conform to ITAR regulations

Any advice as to getting hired with SpaceX?

> How are you going to kick a rocket falling from outer space?

I meant if there was some external force like a wind shear or grid fin/hydraulic line failure that pushes the rocket hard enough on descent to alter it's vertical orientation, those grid fins won't really do much to correct that force.

> Gravity and wind will do the job for you

You cannot control gravity or wind. You just have systems that manipulate those forces. Grid fins are a passive system in that they manipulate the fluid the rocket is in to steer it on course but not to correct drastic attitude alterations.

But again, if the updates to the hydraulic lines work out, then they won't need the active thruster system. Adding an active thruster system is just engineering for worst case scenarios.

Nitrogen cold gas thrusters don't give enough "oomph". Maybe if the rocket was inclined at angles x<10 degrees with respect to the vertical axis it would've been able to correct but this rocket was leaned over at what seems to be 20<x<=45 deg. In other words they wouldn't of have been powerful enough to correct that much of a drastic lean the Falcon had coming down.

But I'm sure with the hydraulic fluid corrections a stronger control system won't be needed to fix large angles of attack but it would be nice to have as an emergency system.

"Have it and not need it/Need it don't Have it" really doesn't work with rockets because of the mass requirements

Those are just grid fins which are used more for steering than attitude control.

If I kick the rocket over those fins won't do any thing because they can't correct the force I applied to kick the rocket over. An active thruster (an attitude control system) can recorrect the force of my kick and reorient the rocket vertically.

I feel if the 1st stage booster had an attitude control system toward the top like the BRAHMOS missile [1], the lean could've been corrected to at least have the rocket be upright when it impacted the platform. Although the choice to add an attitude control system would probably take up more space and add mass which is critical for a stage rocket.

[1] http://i.imgur.com/5RWkvem.gif