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Thomas-
I'm a big fan of Callisto and will keep my eyes peeled for any updates. To me, it seems to be about the only place in the Jovian system of satellites capable of having a safe radiation environment for a scientific colony/refuelling depot. "A nice place to visit, but wouldn't wanna live there." Until we get faster transportation, visitation would probably be from Mars as a starting point.
Agreed about the stainless steels you mentioned, but the Inconels are principally Nickel alloys, since Nickel and Chromium together constitute 65-70% of the metals present, and Molybdenum is also a major component ~10%.
Regarding the Inconel alloys--they have already been used by North American in the construction of the X-15 rocket plane over 50 years ago. There are Inconel alloys available in powder form for 3D printing of intricate shapes, but my recollection from my college days is they are very difficult to machine; they work-harden and use up milling bits at a prodigious rate. This came from a conversation years ago with a (late) friend who had worked for Pratt-Whitney as a machinist.
Rob-
Inconel at the present usage is would be pretty spendy, but given that in is not being "expended" routinely would make the cost a lot less--if it actually works. I took materials and processes in my university courses, and it was what came to mind almost immediately when the presenter began talking about other alloys. The composition is not from really exotic metals, but is expensive based on the supply-demand curve. My concern would be it's ability to be easily worked and rings fabricated from it?
I just watched this very good video on YouTube that seems to address many of the shortcomings of Starship during the reentry:
https://www.youtube.com/watch?v=Oxb1ySJ … WL&index=2
This is very engineering oriented and the conclusions are very similar to those of GW's.
The commenter stated that the issues seemed to be related to control of the reentry attitude. SpaceX already stated that the vehicle's rolling prevented the in-flight relight of a single Raptor. This video made some good suggestions regarding the use of Inconel in the structure.
This commenter also suggested that the cold gas thrusters are inadequate for control of attitude and should be be upgraded to hypergolics.
I was at one time thinking that in place of the "self driving nail" concept that the NASA brain trust (unsuccessfully) came up with would be a reprise of a Red Dragon capsule that contained a fairly heavy rotary drill system almost axially in the capsule, and a system to dispose of the spoil from drilling as well as a sampling system to determine the moisture content encountered. Said drilling system would carry with it a reasonable supply of drilling fluids to assist in the process. Not trying to do anything other than get some core samples maybe down to 25 feet to check this shallow water ice theory? Maybe set this up as a test before hand at the MDR site as an analog"mission?"
When I initially suggested a projects'17 man crew for the first mission, I was weighing potential loss of human life due to TOO LARGE a crew, but in my opinion, more is better (many hands make the work light...). Sooner or later, exhaustion from too many tasks without any break will have serious psychological impact on the mission. We're talking an 18 month stay on Mars, initially. I know that even as a now-retired workaholic, I would need a break sometime during this exciting but stressful undertaking. Give time for everyone to go out exploring for maybe a 10 day jaunt in a Mars rover Not all at once, but as a break when the mission leader sees there is time from a specific set of tasks for crew members to go out and have their experiences of a lifetime.
FriendOfQuark1 is ao occasional contributor to this forum...
The quote below is from email, reproduced here with permission.
Finally, don't forgot about how you are going to "put weight on bit". If you've ever drilled a board with a hand drill, you know you have to PUSH to get the bit to chew wood. Water/Oil drilling is the same. You are going to need 3 times as much mass to get the same effect. Presumably you can source dumb mass locally but it is going to need some engineering done.
(th)
I am quoting this statement because the last "drilling attempt" that JPL/NASA sent to Mars for their seismic probe used a "self hammering nail," and was a complete failure.
If you're gonna send drilling equipment to Mars, have a professional well driller design the system!
Callisto and Ganymede both have very tenuous atmospheres, and Ganymede has a magnetosphere. The atmospheres are both thought to be primarily CO2, and are also thought to have a subsurface ocean of water. These features are helpful for any long-term visits to these bodies. They are tidally locked to Jupiter.
IMHO, Callisto will possible be the first deep space mission goal for missions departing from Mars; possibly concurrent with a mission to Ceres, or another large asteroid or "dwarf planet." One large spacecraft could "do" both Ganymede AND Callisto in a single mission?
Dream Chaser is currently being stacked at Kennedy Space center for it's inaugural flight test to the ISS. It's great to finally see this happening, as it's a well thought out and executed design.
I found this video on YouTube about Callisto; I don't agree with it 100%, but it's dated and was posted 3 years ago.
Human cold tolerance. Something to think about as we head out towards the colder parts of the solar system.
https://maoi.org/blog/whats-the-coldest … n-survive/With proper clothing and preparedness, human beings can survive temperatures as low as -50°C for limited periods. This assumes exposure to Earth's atmosphere with an indeterminate amount of wind chill. The key word is 'survive'. Expecting people to work in those conditions without heated garments is expecting too much.
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I wouldn't expect anyone to be doing "grunt labor" on Callisto, but operating a climate controlled vehicle with robotics capability on the surface would seem possible. This is simply too far out from the Sun to even consider using solar power, so some form of nuclear is going to take center stage. It would seem to me that this could be a great base for a deep space optical telescope for study of the outer planets of Saturn, Uranus, Neptune, and yes, Pluto. The moon is tidally locked, so the glare from Jupiter would be minimal and a permanent observatory would be a great way to spend 4 years of graduate study in planetary astronomy.
Posting this here but administrators may move if necessary.
https://www.youtube.com/watch?v=w6L-dP8 … WL&index=2
This was an online interview conducted by Ellie, on her YouTube channel, Ellie in Space. Many interesting call in questions and discussed the new Mars Research Institute initiated by Robert. It's a lengthy interview of an hour. I watched it in it's entirety. Lots of questions about SpaceX and Elon Musk--all answered in the classic Zubrin manner.
If SpaceX takes IFT-2 as a "learning experience," it won't be a wasted test. I'm willing to place my bets on them using the controlled thrust profile as GW has detailed above in post #47. That would correspond with the Elon theory that "the best part is no part."
I'm sure there will be some changes to the number of engines running during the hot staging next time, and if coupled with the angling of the Starship engines outward and a bit more spacing between the stages as in my initial suggestion, might result in a better outcome. That's why these are called "Test Flights." The real trick will be obtaining enough acceleration of the Starship with the Booster still thrusting along with maybe 10 engines that have been throttled back to maybe 50%?
From all the comments in this discussion, the underlying principle seems to focus on solid ullage thrusters being the KISS solution. I would think that Elon would tend to agree in that regard. "The best part is NO PART" being the epitome of his philosophy. The solid ullage thruster rockets seem to me to be the logical solution., although a hypergolic system would be more compatible with the "reusable" philosophy?
The sheer size of the Booster is part of the problem; requires large ullage thrusters to work adequately. Bigger isn't always better!
Here's an update on the Vulcan-Centaur mission from Space News:
Tory Bruno of ULA has repeatedly claimed the date for Vulcan launch is 24 December. This year.
My suggestions are as given here:
(1) Increase the distance between the Starship and Booster stages, by a small but meaningful increment and increase the size of the hot staging vents.
(2) The pressure of the Starship exhaust on the Booster, as calculated by GW, needs to be reduced significantly through the angle of thrust outwards. I believe the gimbel angle is limited to 15 degrees, so the distance I suggested in (1) above could be calculated on this basis.
(3) Include several ullage solid thruster motors to ensure settling of the LOX and Methane before attempting Booster recovery.
I am unsure about whether or not SpaceX is locked into hot staging, but a lot of thought and good engineering should make it work. This was a new approach and mistakes were definitely made, and it may take some expensive "tinkering" to solve the issues tha have arisen; many test flights with less than optimal results.
As usual, GW details things the way they really are, and not in some fanboy manner. He has elaborated what I said and what Scott Manley stated immediately after the launch and hot staging fiasco. I sent a video that an aerospace engineer published showing what was probably happening in the tanks.
It's now been over a few weeks since the successful launch of IFT-2 and discussion of the problems encountered following the hot staging.
The first decent analysis of this situation arose on a Scott Manley video where his thoughts paralleled mine: propellant sloshing in the LOX and
the methane tanks creating voids which led to starvation of the turbopumps, resulting in failure of the engines to stay functional and restarting problems.
I haven't heard much more from any official sources (i.e. SpaceX), but Scott also suggested that the ignition of the Starship gimbeled engines possibly exerted enough of a blast effect on the booster that there was a negative acceleration that caused the problem. According to other sources of information, the center 3 engines were all deflected outwards to reduce this effect, but if this did occur as Scott suggested, my suggestion for a "fix" is pretty straightforward and simple: increase the gap between the Starship engines and the defector plate of the booster allowing the gasses from the exhaust to better vent sideways during separation. That would allow the angled exhaust to vent rather than hit the top of the booster. Jus a slight modification to allow the geometry to "do it's thing."
I'd be interested to hear what GW thinks about the issue itself as well as my suggested "fix."
This just popped up on YouTube, and is a simulated "tank slosh" done by an engineer.
See my second sentence in post #24, in which I commented on loss of signal from Starlink.