Weekend update...

The stainless motor and test stand are almost ready to test.
Waiting for some more silver screen to arrive so I can make small cat packs rather than wastefully cut up 6" packs.

I worked on putting some more storage and shelving into the garage.
(My son finally gave up on the fantasy that one might someday park a car in there)

Sunday I went out to FAR and worked on getting generator set up for Propellant processing facility. I've never had a gas motor beat me, alas the universe is telling be I'm not a diesel mechanic. Will try again next time on site.

I will be at the SSI.org conference on the 29th 30,31st so if your there say hi.

As a science geek I enjoyed the 4 part videos from LPP power they are trying to do fusion on a shoestring and are being very open about the process. A long shot but if something like this works it changes the world..... Part 1

Composite Compatability tests.

I soaked 8 composite samples in 85% peroxide for about 5 hours at 70F.
Top Row:

• Epoxy with no fiber
• Glass fiber in epoxy
• Kevlar in Epoxy
• Carbon in Epoxy

Bottom Row: Vipel 010 Chemically resistant vinyl ester

• Vipel Resin no fiber
• Glass fiber with vipel
• Kevlar with Vipel
• Carbon Fiber with Vipel.

Experimental setup.
I set out 6 polyethylene cups with 300ml of 85% H2O2.
I tied polyester cord to each sample and placed them in the H2O2 solution.
They were placed so 75% of the sample was covered.
The Pure resin and glass fiber samples with the same resin shared a cup.
I put a clear polyethylene bag over each cup.
I periodically observed the samples.
I left them in the sun for ~5 hours.


The bags of 4 of the sample cups were clear, the bags over the two carbon fiber samples has fogged condensation on the inside of the bag. This seems to indicate some H2O2 decomposition.
It was not enough to measure any significant volume change.
None of the samples had shown any significant h2o2 decomposition. They were filled to 300ml +/-10ml and at the end they were all 300ml +/- 10ml.

I then removed the bags off the top of each cup with a long set of tongs.

After the 5 hours I was hesitant to handle the sample or move the containers as I was possible I'd created a hazardous solution. So I could not weight the samples.

After 5 hours the epoxy samples all had a layer of something floating on the top of the H2O2.
The Vipel samples had no visible contamination of the h2O2.

Then one by one for each sample (except the pure resins)

• I grabbed the loose cord tied to each sample with the tongs, carried them over the the wire fence and hung them on the fence.
• I then shot the sample with a 243 winchester with 85gr bullets from about 25 ft away. The impact velocity was 900 to 1000 m/sec.

None of the samples showed any sign of detonation or any increase in energy release from the rifle shot. I did not shoot the pure resin as I expected the pure resin would shatter and not provide any additional information.

After determining that none of the samples detonated I then individually dumped each h2O2 container on the dirt. (Mojave dirt is a great decomposition catalyst.) No notable difference in energy or release was noted.

I then removed each sample from the fence and soaked them in water to remove the peroxide.
The samples are shown in the picture above. The Vipel samples showed some surface etching, ie they had an oxide layer on the surface, but showed no significant structural degradation.
The epoxy samples wer reduced to bare fiber. There was almost no structure left.

In the picture both bare resins look discolored, but the Epoxy is bubbled and distored, where the layer on the vipel is just a surface layer its very thin. It almost looks like the oxide layer aluminum gets after a lot of peroxide exposure.

The company that makes the vipel F010 has an even more resistant resin, K190 that is harder to get. The K190 is rated for 50% peroxide at 100F for years of service.
Their chemical compatibility guide

When I'd finished pouring out the peroxide in the 6 cups I had a 100 ml or so left in my transfer cup. So I put a bunch of raw kevlar with no resin in that cup. It had ZERO reaction of any kind, no bubbles, no discoloration, no steam on the bag etc...

First test part in the bag

My first tank part attempt is in the vacuum bag and should be curing. Its been 90 minutes since I mixed the resin and its still fluid and not getting warm yet....I hope I converted drops of hardner to grams correctly for the resin mix.

It is a cold evening so.....it could just be slow

Having resin that does not go off makes a nightmare.
In any case I doubt the first attempt will be pretty....

Update the resin in the mixing cup got hard, I peeled the vacuum bag blotter felt and peelply and the underlying composite is still tacky. (Its really cold and damp in San Diego today so I'll let it sit another 24hrs.)
.

Tanks the other hard part

The Rocket Equation has a term that is the rocket motor efficiency and a term that is the mass ratio. In a pressure fed system the biggest component of that mass ratio is the tank.
If I could make a tank identical to a 2L soda bottle only 5 to 10 times bigger that would be almost ideal. I could probably find a mechanism, to join a bunch 2L soda bottles and I may pursue that, but I'm also going to try my hand at composite tanks. Toward that end I made mold forms for a 6" diameter cylindrical test tank mold. I heated it up and waxed it with mold release and setup the vacuum bag etc.. got ready for my first composite test part.

I have something non-rocket to do tonight, but tomorrow I hope to try making my first composite part since the solar plane project.

The first tanks will have glued Mylar liners that are not H2O2 safe, but the flight tanks will have mylar/PET liners with no glue. The jury is still out if the tanks will be seamed via vacuum heat, sonic welding, or RF welding.In addition to the liner I also want the tank to be chemically resistant to the H2O2. I want any liner failures to not be immediately catastrophic.

I'm getting a bunch of samples and setting up to do compatibility testing next weekend out at FAR. I'm testing glass, kevlar and carbon fibers with normal epoxy, vinyl ester and special chemically resistant vinyl ester resins. My gut says that plain E glass with the chem compatible resin will be fine, I'm almost certain that carbon with epoxy won't be. I hope the Kevlar and chem resistant resin also work as the kevlar is a bunch stronger than the glass.

Its a multi part test, start with 30% and work your way up to heated 85 or 90%. Anything past 50% really has to be done remotely. I'm planning to soak samples in PET soda bottle bottoms. sitting in hot water on a hot plate. The sample will have a string and pulley so I can pull the sample out of the solution remotely and shoot it with the 243. I could set up some kind of hammer and anvil test, but I worry that if it goes bang, the hammer becomes a projectile.

I figure I'll get the preliminary screening done this weekend and the samples that pass will get the hotplate test in two weeks.

A few ideas and loose ends

This week I learned that the NASA Nanosat prize is funded, (I thought it was a proposal not a funded prize.) So this clearly puts a bulls eye on a project target. This process starts with a notional vehicle and works backwards from the last stage. With a 1Kg payload I think that I can build a three stage launcher with a gross liftoff mass of less than 1000lbs.
To do something on this scale every gram matters. I'm starting to designbthe best 3rd stage I can and works backwards... (If you do a good enough job you only need two stages)

One needs:
Efficent light high expansion motor. Working on small motors via the DMLS project.

Really light tanks.....I've purchased all the large beverage containers I can find and am weighing and pressure testing them. So far the best tank is a 2l soda bottle. 100+PSI and mass ratio of > 40. A single soda bottle is not really enough. Any scheme to group them together is heavier than the bottle. So I'm looking at maybe fabricating my own tanks. The idea H2O2 tank would be mylar lined (mylar is another version of PET like in soda bottles) with chemically compatible resins and kevlar. Normal Epoxy and normal Carbon fiber are not happy with H2O2. All the tanks at this scale are up against minimum gage issues so whatever pressure you get in the tank will be more than really needed. In concept these seem very similar to the H2O2 tanks shown by Richard Speck of Micro-space at the 2007 LLC. I've got most of the materials to try this on the way. The biggest unknown issue is how to build the liner. If I can make the process in patent #3661675work that would be ideal.

Really light valves and actuators... probably all based on brushless model airplane servos. one can get lighter brushed parts, but must trade against the requirement to put them in a pressure box and the smallest brushless ones seem to be a win.

Guidance.... more on that later...


Regulation... This one is hard because the regulatory framework that applies to orbital launches is tailored toward something like a big Atlas. My current concept is to make the 2nd and 3rd stages really light and fluffy. Almost all plastic, including the valves and plumbing. Only the thrust chamber will be non-plastic. The first stage will probably be metal. The concept is to launch off shore so that thrid party safety from the first stage is constrained by physics and the 2nd and 3rd stages are too light to survive reentry. The real trick will be proving that and path taken by the 2nd stage will either burn up or land within the 1st stage constrained by physics zone. IE if it shoots straight back down its not going so fast so it might burn up. If it flies perfectly by the end of its burn then its going to fast to survive reentry. The question is what happens between these two zones. My nominal vehicle meets all of the amateur limits except the no orbit allowed rule. IE less than 200Klb/sec and orbital altitude less than 150km. (Rules say you only need to go around once.) more rambling to follow as I figure things out.

Anyone in SoCal with access to a 14" diameter 20" long vacuum oven that I could use to try the process described in the patent above would be really helpful.

More Printed Motor news...

The DMLS machine that is most common is an EOS270. The company that makes these machines has recently started adding some new materials. The new Material I'm most interested is Aluminum for chambers, and maybe Inconel 718 for a possible turbo pump.

I'd gotten some chamber quotes a year or so ago and it was still too expensive. When I had GPI quote my design again this year it was half of what last years quote was and I ordered the part on the spot. (In Stainless) GPI was also very helpful in making geometry suggestions that woul d improve the quality of the resultant part.

After placing this order I thought I'd do some more price research and sent the same file to Morris Tech to quote. The response from Morris was very competitive and its clear that this industry is seeing significant price declines. (Neither vendor knows what the other quoted) I hope its a sustainable trend and not a bloody battle to bankruptcy.

I really don't like beating vendors against each other because any long term relationship needs to be win-win and you can't do that by abusing your vendors. While it might be tempting to beat vendors prices against each other, its not some thing I do.

I also asked both Morris and GPI about the availability of Aluminum.
GPI indicated that they would soon be running Aluminum and Morris indicated that they had already run some Aluminum parts and that in the next few weeks they would be running some more aluminum test parts.

Since I was doing interesting stuff as an individual inventor not a big corporation Morris offered me the chance to add a single part to the Aluminum test run for approximately their direct cost. Its an offer I can't refuse. So I will soon have small DMLS chambers in two materials!

The Aluminum Motor is actually a bit bigger than the stainless motor as it needs to be cooled the whole length with a stainless cat pack support thermally isolated from the cooled aluminum chamber as a sleeve inside.

So if you need DMLS parts there are at least two really awesome DMLS vendors in the U.S.

http://www.morristech.com/
and
http://gpiprototype.com/

Why the motor has horns.

If you look at this post from July. You will see how the finished motor will look. Rather then spend lots of $$ making the simple upper section I only had the lower part printed with DMLS. The upper section where the cat pack will go is fabricated in the normal way from a sanitary fitting. It will and then be welded to the motor bottom.

The horns sticking out the side are the fuel feed. The fuel goes in the curved part and a 8-32 Set screw with a orifice drilled in it goes down the straight section. Then the end of the straight section gets plugged. You can buy predrilled orfices in 8-32 set screws from Mcmaster Car.

Here is a picture of all the bits before welding:

The two small parts are the machined elbows to connect the vertical feed tubes with the Chamber top.

Stainless Chamber bottom on the way.

I received this picture today:

Pressure Fed Upper Stage.

I've been doing some calculations on what an upper stage for the 1Kg Nanosat launcher would look like. One of the interesting twists is that if the motor only has to run in vacuum then it's ISP is almost independent of chamber pressure. So for any small launcher you are going to have minimum gauge problems long before you hit the minimum optimum tank wall thickness. This opens the possibility for tanks with things like 3L soda bottles and PVC valves. It makes me wonder why Space X went with the turbo pump 2nd stage for the F9. a lot of complexity for very little gain? Maybe just because they had one that was approximately the right size.

Some progress...

This weekend I worked on cleaning up my Garage.
I cleared the floor, two junk Tables and a cart. Everything I cleaned up now has a place. I still have piles on one bench and one cabinet. When those are done I need to start the task of going through all the storage containers, drawers etc.. and purge stuff I'm never going to use. A little bit more room would be really helpful. All in all I feel a lot better about the garage after putting three full days into it.

My Son and some of his friends went to burning man so just as I start to get a handle on the garage the truck comes back from Burning man filling the garage with dust covered stuff..... they have been working evenings getting it cleaned up so I can't really complain.

I tried to fill the porosity of my printed motor with some solder and I just could not get good penetration. It didn't stick to the stainless even using some fairly aggressive acid flux. As a result I redid my printed motor design for the DMLS process and had it quoted by GPI prototype. Their price was about 4X the Shapeways price, but the part is thinner and needs a lot less welding. (Its also about 2/3 of what I though it would be.) I ordered it Tuesday, so we should get it some time in the next two weeks. The parts on the DMLS "showcase" always look incredible. I asked them to give me the best possible price so please give it to be raw off the machine. It will be interesting to see the raw finish.

An Orbital Vehicle Part 1

What does it take to build an orbital vehicle?
My interest is in something really small say a nano sat launcher. This is going to require more performance than a larger rocket as air drag has so much more effect. I'll start with John Whiteheads paper. For a LOX Hydrocarbon stage to get to a 200Km orbit he says we need ~9500 m/sec Delta V and for a 1T vehicle. This paper claims this was a simple analysis, and I always like to cross check. From the Falcon 1 Users guide table 2-1 we get the following:

2nd stage:

1200lb empty

8900 lb propellant

400kg (880lb) payload

317s ISP

Using the rocket equation I get 5173 m/sec DV

1st stage:

3000 lb empty

47380 propellant

10980 lb Payload(The 2nd stage)

300 s ISP

Using the rocket equation I get 4353 m/sec DV

Total DV 9526 m/sec

Extrapolating in the "How Small" paper we get about 9250 for a Falcon 1 sized vehicle. So I have a source to give me some target numbers and have independently verified that the numbers are not wildly off. So we need to design a vehicle with 9700 m/sec of Dv to go orbital.

The 180 sec LLC vehicles needed 1765m/sec DV. So orbit is a whole bunch harder. We could use the LLC L1 level of technology and stage 5 times this would weight 750K lbs. Clearly we need to do better. All but the first state will run in vacuum, they don't need to throttle, we don't need landing gear, so we should be able to do a lot better. My initial spread sheet says its quite possible with a three stage H2O2/Hydrocarbon vehicle. To do it in 2 stages would require developing a lightweight pump or making the vehicle really big. I'm going to refine my inital guess and publish it in the next week or so.

Keeping a neat Shop...

My review at my first ever "real" engineering job said something like:

"Paul Moves his assigned projects directly to the desired result with exceptional speed and skill leaving a trail of destruction in his wake."

This was a job where we built real prototype hardware controlled by electronics and
some of the earliest embedded computers. (6502 anyone?). I got the Job done but I left a wake of debris behind. Not much has changed. My rocket shop occupies a two car garage and a 8x10' office at my home. I find the continuous mess and inability to find things is probably the biggest frustration in my life.

I intellectually realize that I'm whining about my own personal shortcomings and should just gut it out and clean up my space. In my life I've never achieved that for any period of time measured in units longer than an hour. So I'm asking my readers if anyone has successfully overcome the this particular demon? I'm open to suggestions?

Its really a two part problem

Part One I have way to much stuff crammed in too small a space. So it needs a Major organizational redo. ( I can actually envision someday solving this part of the problem.)

Part Two once everything is organized how does one maintain cleaned up?
The Failure Scenario goes something like: Come home from work, family is going to have dinner in an hour so I go out to garage and start machining a pressure test plug, then dinner is called and I go in and eat... not to return to that project for a few days. This is complicated by the fact that I often have half a dozen partially finished projects in work at one time and I work on the different projects as I'm inspired to do so. This is not a complete failure as I actually do finish a significant percentage of what I start. (It may take 12 calendar months on a project that is only one real week of work)

Some specific questions for comment:

How do you handle partially finished projects in a way that you can efficiently task switch without leaving piles of half done all over the shop?

How do you decide when to throw something out?
Our current rule is if it is not a tool and has not been touched in (Replacement Cost /25) months it goes in the trash. If the value is over $250 it goes in the ebay pile... (The Ebay pile may someday actually make its way onto ebay)

How often do you redo your storage systems.....
How much dynamic range to you leave for expansion?
IE I have a drawer for AN male elbows. When I create the drawer its 25% full, a year later its over full and won't close so it sits on top the pile....


Has anyone ever tried to hire someone to clean up/ maintain their shop?
How did that work? How did you find such a person?
In So Cal one can find lots of low skill labor that will follow directions, but I think I really need someone that knows the difference between a drill bit and a mill bit, a servo and a valve etc...

Do you think it would be possible to hire a Science/Tech interested high school student to work on this without leaving them emotionally scared for life?

Getting back to rockets.

I've been working on several different projects. My printed motor looks finished, but when I pressure test it leaks EVERYWHERE so I can try to fill the pores with tin and silver solder being careful not to clog cooling passages or get silver where it shouldn't be, (Silver is catalytic with H2O2) or I can see if I can afford having the part made by the better DMLS process. I just sent out a modified 3D model to have that quoted.

I have my custom GPS front end digitizer done and most of the FPGA work done for fast correlation hardware , but I have not put all the parts together and applied power. I hope to get to that in the next month or so.

I also have a few small electronic projects I committed to do for FAR infrastructure so I need to spend some time on that this month as well.


The potential NASA nanosat launcher prize may change my path, but I'm still thinking the year or so out goal is a reusable vehicle that can go to 100Km and back. It will be much smaller than the Masten and or Armadillo plans. It will also look more rocket like.

Four years ago I bought an 02 Dodge Ram 1500 Crew Cab to drive back and forth to the desert in a reliable comfortable truck. I've since put an additional 110K miles on it and two weeks ago Sunday it tried to kill me by blowing out the rear end and locking up the rear wheels. I spun it pretty hard, got it on two wheels, but did not flip it or hit any thing. I knew I eventually had to replace the truck, I'd just spend 1K getting the truck all ready for the fall rocket season,
new brakes, AC system cleaned up etc...

I have a general rule that I don't let a vehicle strand me more that twice. The dodge already left me stranded about a year ago with a blown water pump, this was its second misdeed. So I went out and bought a year old 09 Super Crew F150 It has 17K miles on it and I got a good deal. This sets the rocket budget back a little bit, but business seems to be recovering and it should not be a big issue much beyond the first of the year.

I'm actually getting excited about working on rockets again and hope to get back to regular progress in the next month or so.

NanoSat Centennial Challenge

The cost of getting to orbit is the real barrier to space exploration, settlement, and harnessing of off earth resources. The difficulty of the problem makes it hard for small innovative organizations to have a shot at making a launcher for commercially interesting payloads. Doing a nanosat launcher is not as difficult. The New NanoSat contest looks very good. If I had the resources to offer a significant prize it would look very similar to the NanoSat prize. I'd add some bells and whistles like a bonus for a reusable vehicle and a junior league 100gm category, but all in all it looks almost perfect.

More printed Motor Progress

The printed Motor parts are all here, I have a few things to finish and it will be ready to run.
I made the tubes for the fuel input too short and connecting to them is going to take some creativity. The end cap with o-ring grove, clearance for flow and fingers to push down on the cat pack turned out well:
:
I've sent out the order to get the catalyst retainers water jet cut.
All the bits and pieces should be here by mid month. If I will decide to brave FAR/Mojave in peak summer is a different question. There is a real possibility it won't get tested till mid to late September. Business continues to go reasonably well, this means that I should be able to ramp up my rocketry projects after the first of the year.

Parts Came in...

The sheet of paper the parts are laying on is 8.5x11"
My Welder Sent me this Picture . He still needs to weld the bottom manifold on,
When I ordered this version I did not order the bottom manifold because I had one. alas I was showing the previous version to people and either I left it at FAR, or someone walked off with it.
I've ordered another bottom manifold ring it will be two weeks or so.

Some Data

I've now flown the simple instrumented HPR 5 times with data recording.
I've learned some things

Flight 1 at FAR Spark fun IMU, GPS and 6DOF Analog devices ADIS16360
GPS did not work at all, Spark fun was noisy, ADIS16360 worked reasonable well

Flight 2 At FAR, shorted battery cable, only goy Spark Fun IMU data.

Flight 3 at Plaster City (Yesterday) OpenPilot 10Hz GPS and ADIS16400 Analog deivces IMU.
GPS lost lock moments abter ignition (10 G or So) ADIS data all looks good.
On board recorder did not work, only have down link telemetry.


Flight 4 at Plaster City (Yesterday) OpenPilot GPS and ADIS16400 Analog deivces IMU.
GPS kept lock till parachute deployment (where the GPS is now pointing at ground).
Take off was only about 6-7G, while the GPS says it kept lock, the altitude data was wrong and did not follow the flight path, onboard data recording worked correctly. (A few minor drop outs, I think the data recording connector is intermittent)
Flight 5 At plaster City Same setup 10-12G launch, GPS lost lock, ADIS16400 data looks good.
Telemetry log only, on-board recorder did not work.


Things I've learned:

• The $125 Spark Fun 9DOF IMU does not like rocket vibration, and the accelerometer saturates on the rocket.
• The $500 ADIS16400 is really pretty good, the data is clean and seems to make sense.
• The low cost 10Hz GPS's are not happy with high acceleration. (To be expected)
• The Max stream 900Mhz Xbee seems to be reliable even with grossly sub optimal antennas.
  

My goal is to develop a low cost system, buying a 5K GPS and 10K IMU are not part of the program. I'm really happy with the analog devices IMU, now to solve the GPS. I have one more
gps to try the new Novatel OemStar, I suspect that it may do better, but it is not available in a form that does not have the COCOM limits. I really do want to develop a vehicle in the next 12 months that will exceed 1K knots and 60K ft at the same time. There is an open GPS project based on the old Novatel SuperStar, alas the super star hardware is not available anymore and the base band chip set used on that receiver is not available. I can buy a Novatel receiver that is unlocked but it would be about 2K. As I've said several times this year, I currently have more rocket time than rocket $, I can continue to do interesting things with my leftover LLC hardware, but it does not match the far end goal. The far end goal is a 100Km 5Kg payload rocket that is reusable and can be reproduced for less than 10K.

In the past few years there have been a number of interesting papers, and even some 100% open projects on building software GPS receivers with just a simple front end. There are also a number of GPS front end chips and module assemblies that will directly feed such a receiver.
In looking at these projects its clear to me that a high dynamic GPS receiver with real time 10Hz updates is still beyond state of the art for realtime software only receivers. I want to do some experiments in this area, so I'm bread boarding a MAX2769 GPS front end chip a small FPGA and a high data rate SD card to record about 60 seconds of GPS front end data. So some time in the next month or so I hope to fly a payload that records GPS front end data and can be post processed with the open source software GPS receivers. If this works I might think about developing a 100% open Tightly integrated GPS/IMU using these peices, with the high rate code and carrier loops in an FPGA. Having the IMU data available at the code and carrier phase tracking level can really help the GPS keep lock. The short version is I'm crazy enough to contemplate building my own GPS receiver as I can't find one that meets both my cost and performance targets.

For anyone that cares the raw data file for flight #2 at plaster city is here: http://www.rasdoc.com/data/

The GPS data is at 10Hz and unmodified, the ADIS16400 is shown in the $AIMU lines.
The data is raw from the ADIS16400,(look at that data sheet) the order is Ratex, Ratey, Ratez, Acel X, Acel Y, Acel Z, Magx, Magy, Magz, extra. (I recorded one too many fields)

This flight was a lower acceleration flight on a rocket with big fins so it made a fairly sharp turn into the wind and the flight path was more parabola than straight up. The parachute deployment was also fairly late and abrupt. Looking at the Magnetic data it looks like the rocket rolled about 5 revolutions during the boost phase.

Way to go Spacex!!!!!

From the video feed I saw that launch looked perfect.
Way to go spacex!!!!

Good luck to spacex.

I'm eagerly awaiting the spacex web-cast to watch the first F9 flight.
I sincerely hope they have a perfect flight.
It is a new rocket on a first flight so a perfect flight is unlikely.
If they have a problem it will most likely be something they could not test on the ground.
If I were to guess my biggest worries would be:

• First stage pogo oscillation, the Saturn V had significant issues with this.
• 2nd Stage ignition in vacuum, the first stage Merlin's have a fair bit of ground side support equipment, so the air start is a differnt beast. (The first hotfire scrub was do to an incorrect valve in GSE) A turbo pumped motor is a complex piece and getting the whole choior singing in tune on the first attempt in vacuum is tricky.

BP Oil spill and Space Robots

If you have been a long time reader of this blog you probably have a geeky desire to see all the technical details. I've been watching the BP spill response with morbid fascination.
BP looks like it is being very open with the technical aspects of its response.
just take a look at all the videos on this page, the scale and scope of the operation are mind numbing. If that link does not work as a permalink, just look for the June 1 Videos on the LMRP, or go back and watch all of Kent Wells presentations.

I've been watching the the technical videos, diagrams and briefings for at least the last two weeks. I think this whole thing could be used as a pretty detailed response to those space scientists that say don't send humans, send Robots. With the BP spill we have lots of very sophisticated ROV's ,they have reasonable access to the surface for repair, adjustment and tool change out, a round trip operating delay of ~10 micro seconds and yet the whole process looks painfully hard. Trying to do any serious resource extraction or heavy construction remotely without direct onsite human intervention is currently significantly beyond state of the art. We need Humans on site.

We need humans in space. Go F9-Dragon!