Russia Progress freighter lost during launch
Due to what appears to be the failure of the third stage of its Soyuz rocket, a Russian Progress freighter bringing supplies to ISS was lost.
The Russian space agency — Roscosmos — confirmed the demise of the Progress MS-04 cargo craft in a statement, saying the automated spaceship was lost as it flew nearly 120 miles (190 kilometers) over the Tuva Republic in Southern Russia. Engineers lost telemetry during the Soyuz rocket’s third stage engine burn, and most of the vehicle’s fragments burned up in the atmosphere, Roscosmos said.
The consequences of this failure are numerous:
- The cargo failures to ISS have been a continuing problem. Despite significant redundancy, every single cargo freighter has had failures or delays in the past two years.
- The failure of the Soyuz rocket is a major concern, since this is the rocket that we depend on to bring humans to ISS. Nor is this the first time this year that the third stage had issues. In May the third stage cut off prematurely.
- This failure, combined with the other quality control problems Russia has experienced in the past few years with the Soyuz capsule and the Proton rocket, adds to the concerns.
It now becomes even more imperative for the U.S. to get its own manned spacecraft capability back.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Due to what appears to be the failure of the third stage of its Soyuz rocket, a Russian Progress freighter bringing supplies to ISS was lost.
The Russian space agency — Roscosmos — confirmed the demise of the Progress MS-04 cargo craft in a statement, saying the automated spaceship was lost as it flew nearly 120 miles (190 kilometers) over the Tuva Republic in Southern Russia. Engineers lost telemetry during the Soyuz rocket’s third stage engine burn, and most of the vehicle’s fragments burned up in the atmosphere, Roscosmos said.
The consequences of this failure are numerous:
- The cargo failures to ISS have been a continuing problem. Despite significant redundancy, every single cargo freighter has had failures or delays in the past two years.
- The failure of the Soyuz rocket is a major concern, since this is the rocket that we depend on to bring humans to ISS. Nor is this the first time this year that the third stage had issues. In May the third stage cut off prematurely.
- This failure, combined with the other quality control problems Russia has experienced in the past few years with the Soyuz capsule and the Proton rocket, adds to the concerns.
It now becomes even more imperative for the U.S. to get its own manned spacecraft capability back.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Soyuz manned rockets have been extremely reliable but the increasing number of failures in Russian rockets is very, very worrying. I’m not a fan of the huge amount it costs to run ISS, but it would be a shame if it had to be abandoned due to a failure in a manned Soyuz launch. Hopefully manned dragon well be ready soon, though last I heard it was delayed again unfortunately.
Or the failures will make them finally have the crew stay there for 2 years at a time! It would be safer, cheaper and give more valuable data for a mission to Mars.
I fear that we had premature hopes, last year, that the quality control (QC) problems were being solved in Russia. When Russia had some successes, after recovering from their last failure, we were hopeful that they were solving their QC problems. when they had a mishap last May (although the launch was successful), they took their investigation seriously, and this was another good sign. Today, however, they seem to have a terrible setback.
Robert wrote: “every single cargo freighter has had failures or delays in the past two years”
The Japanese HTV continues to be used, occasionally, to resupply the ISS but has not yet had a failure, however, its latest launch, in 2015, was delayed from July to August. The good news is that (from the article linked, below) “none of [the delays] appear to involve HTV itself or the H-IIB launch vehicle“.
https://www.nasaspaceflight.com/2015/08/htv-5-kounotori-launch-space-station/
(Yes, Robert, I was checking your facts, because I remembered it succeeded, but I didn’t remember the delay. I should have, though, because there was starting to be concern that ISS could run too low on consumables.)
For those who remember Europe’s ATV, it is no longer being used to resupply ISS. Its last launch was in July 2014.
LocalFluff,
I agree. It would be nice if they could find a way to keep crews aloft for extended missions without having to worry about the adverse health effects on long missions, such as bone loss and vision changes, becoming worse than they already get. In order to get to 2-year missions, they need to gradually extend missions and test solutions to such problems — when they come up with proposed solutions or improved solutions.
I am hoping for one or more rotating space stations, in the future, to give artificial gravity. Then we can find out if this artificial gravity is a solution and what gravity level is needed to solve the problem.
Excuse a question:
What– the transporter doesn’t work?
But seriously–
Is there a reason they don’t keep an empty re-entry module, docked at the ISS?
How long is a Soyuz spacecraft rated to remain on station? I thought it was something on the order of seven months.
Is there a body of research anyone can direct me to, concerning innovative (or fanciful) methods to get from LOE, back down to Earth?
I appreciate there is no graceful way, to climb out of Earth’s gravity well & the atmosphere.
Are there any ways to gracefully “climb back down?”
Our does this ultimately all involve friction, parachutes, retro-rockets, and heat-shields, & combinations thereof?
(I have to believe the RAND corporation studied “escape-modules” of some sort, at some time. ?)
There goes Santa’s delivery!
Wonder if anyone in Siberia smelled burning Christmas dinner.
I hope Space X gets back on schedule soon.
Third stage of Soyuz U with Progress M failing after 323 and 325 seconds today and on 24 august 2011. Looks like they haven’t fixed the problem.
2 years stays on the ISS is safer because launch and landing is much much more dangerous than microgravity. Launch and landing has killed all 18 astronauts who died during spaceflight. Microgravity has never even injured anyone of the 545 astronauts who have been in orbit up to the record of 14½ months. 2 year stays would cut health risks by 75% compared to 6 months stays. Imagine what would happen if a crewed Soyuz (50 years this week, happy birthday!) burns up in the atmosphere. The ISS would be abandoned and destroyed.
Mitch/’Fluff– good stuff.
Richard Feynman always wanted to visit Tuva.
tuva or bust
https://youtu.be/eZgZUPRdHZY
1991 book called “Tuva or Bust,” chronicles Feynman’s attempts to get permission to travel.
(His daughter made a ceremonial visit about 10 years ago.)
wayne asked: “Is there a reason they don’t keep an empty re-entry module, docked at the ISS?”
Kirk is correct. There is a lifetime for a Soyuz on orbit — or any spacecraft. The driving factor depends upon the spacecraft and its design. When docked at a space station (MIR or ISS), a Soyuz lasts longer on orbit, but it still has a limited service time. My understanding is that the Soyuz, flying independent, is limited for the crew to less than a week (combined up and down travel) by air supply. Soyuz is not a moon ship but is a space station ship.
Until Bush cancelled it, there was to be a Crew Return Vehicle at the ISS for long periods before needing replacement, but I do not know how long any of the proposed designs were able to last while docked to the station.
wayne asked: “Are there any ways to gracefully ‘climb back down?’”
I kind of thought that the aerobraking reentry and runway landing of the space shuttle “was” the graceful way back down. It does not take too much retrograde thrust to slow a spacecraft into the atmosphere. From LEO, it takes somewhere around ¼ km/sec, which is about 3% of orbital speed.
Another possibility is a space elevator. This concept can take a payload/satellite/people into space, but it could also bring them back again.
https://en.wikipedia.org/wiki/Space_elevator
The latest thinking for these is to use a ribbon of high-strength nanotube threads, but earlier versions were to build a large tower into space.
As you may have noticed with the construction of tall buildings, it is difficult to build structures that are miles high. Thus the “cable” idea was proposed once the light weight and high strength of nanotubes made a space elevator theoretically possible.*
The only stable circular orbit that a space elevator could take a payload to is Geostationary, but other orbits can be achieved with the use of some propellant, “old-school” style. However, a space elevator should save a lot of fuel on launch and put fewer stresses on the payload with a smoother, although much slower, ride into space.
Although a space elevator could bring a payload back down, it may take more propellant to get to the elevator from a given orbit than it would take to reenter the standard way.
LocalFluff,
You wrote: “Microgravity has never even injured anyone of the 545 astronauts who have been in orbit”
This depends upon what you mean by injured. Bone loss and vision changes count in many people’s books, especially the affected astronauts. Do not take them lightly.
The risks of launch and landing are fairly low, these days, but the risks of bone loss and vision damage are high. They count for a lot, especially for those who need to maintain excellent health and vision in order to remain flight qualified. For American astronauts, distant and near visual acuity must be correctable to 20/20 in each eye. If long flights cause too much damage, then they stop being flightworthy.
* Two problems with space elevators are stability and space debris.
Every time a climber, with or without payload, went up or down the elevator there would be Coriolis effects that would tend to cause the cable (or even a structure) to swing like a pendulum in the east-west direction. Gravitational effects of the moon and the sun would tug the cable (or even a structure) in the north-south direction. This perturbation already occurs with Geostationary satellites, and every once in a while they perform a stationkeeping thruster burn to stop the north-south portion of their perturbated orbital trajectories.
As you may already be thinking, a solution is to have stationkeeping thrusters at various altitudes along the elevator to correct for these instabilities.
The second problem is especially bad at Earth, but not yet bad at the Moon or at Mars. Every object in Earth orbit either crosses the equator or orbits on the equator. Since the space elevator extends upward above the equator, as it rotates with the rotating Earth it will cross the orbit of every active or inactive satellite and every piece of space junk. Twice a day.
Although this only will be an immediate problem when the orbital object and the space elevator are at the same point on the orbit at the same time, it could take a while for the first object to strike the space elevator – but it could have catastrophic consequences, such as separating the elevator and sending it off into its own Earth orbit, meaning that tens of thousands of miles of “tether” would be loose in orbit, potentially threatening everything else in orbit. The Earth-anchored lower portion of the cable would fall to Earth. Outside of thoroughly cleaning Earth orbit, there is little that can be done about this problem.
Years ago, I mentioned this to one advocate of space elevators, and he thought that the cable could be moved, using thrusters at various altitudes, to avoid debris and dead satellites, but as we have seen with the February 2009 collision of Iridium 33 and Cosmos 2251, it is already tricky to prevent two satellites from striking each other. My discussion with him was before this collision, so his thoughts on collision avoidance could be different, now.
Soyuz launcher drops its launch escape tower 157 seconds after take off. This has now happened twice 167 seconds later. I don’t know what the options are if this the third time happens to a crewed Soyuz launch, but it doesn’t look good.
Edward,
Space elevators are unbuildable on Earth. On asteroids, Phobos and Deimos they are unnecessary. The Moon might have the right mass, but its eccentric orbit and irregular mass concentrations cause instabilities in Lunar-stationary orbit where a space elevator would have its center of mass. An elevator is an inflexible vulnerable logistical nightmare anyway, like a single lane bridge. But a rotating wire in space that can exchange momentum between spacecrafts going both ways might have something going for it. This blogger has made several well illustrated posts about the “Rotovator” concept:
http://hopsblog-hop.blogspot.se/search?updated-max=2016-07-22T18:25:00-07:00&max-results=7
LocalFluff wrote: “Space elevators are unbuildable on Earth.”
The classical version is unbuildable, but the nanotube ribbon or cable version that is a decade old is not built bottom up but is unreeled from orbit down to the planet. Theoretically, this is buildable.
In practice, this version is the equivalent of a tether, and we do not have much experience with the behaviors of tethers in space. For instance, it would not unreel straight down, because the lower end would be traveling at thousands of miles per hour, so as it approached the Earth, it would appear to travel forward relative to the reel in the higher orbit. In essence, the lower end would be in its own orbit (as well as every incremental length of the tether/cable/ribbon), except influenced by the forces tugging on it from the rest of the tether. I would expect that a thruster(s) would be needed to slow the lower end and guide it down to the Earth to the anchor point.
A similar problem would be experienced building one on any other planet, moon, or asteroid, too. Building it may be tricky, but it should be buildable. More experience with tethers and how they behave between orbits is needed to be sure of the buildability and usability.
Similar control and stability problems occur with the Rotovator. It all looks well and good when drawn with straight lines, but the reality is that these tethers and space elevators will curve and flex, and they will not be straight.
The Rotovator’s orbit will drop each time it lifts something to a higher orbit. There will be energy and momentum transfer, and this is why the author thinks it is a good idea to bring things back to Earth, to raise the orbit again. However, with each “throw” of a payload upward, the grabber end of the tether of the Rotovator must be kept from dropping so far into the atmosphere that it slows down the whole assembly due to atmospheric drag, which would eventually cause the whole thing to fall back to Earth.
I am very much in favor of trying out these ideas as well as exploring tethers in general. Tethers may (or may not) have a large number of uses in space transportation, space propulsion, and maybe even other purposes. We just do not know, yet, how to properly use or control them or what problems we will find when we get around to trying them.
Edward,
Space elevators from earth are indeed impractical. Besides lack of tether material with a high tensile strength, there’s also the problem of orbital debris. With all the junk in low earth orbit, the elevator would suffer frequent impacts.
LocalFluff,
You write “On asteroids, Phobos and Deimos they are unnecessary.”
One could just as well say on hands, slings are unnecessary. After all it’s easy for a pebble to roll off the palm of my hand.
You see the flaw? A sling’s purpose is to impart velocity, not get the pebble off the hand’s surface. And an elevator on a small body could be a sling. It would impart delta V as well as get the payload off the ground.
Also in the asteroid belt, ion drives would be a better way to get from rock to rock. But an ion drive doesn’t have the thrust to weight ratio to get off the surface of Ceres, Vesta or the larger rocks. But an ion drive could dock with an elevator anchored to Ceres or Vesta. And an asteroid elevator could also provide a rocket ship some of the delta V needed for insertion to a transfer orbit.
As I post this comment, I am being asked to fill out fields for name, email, and website. For website I will put the page looking at benefits and materials needed for various stages of an upper Phobos elevator.
Hop David,
Read the footnote on my December 1st comment. I explain that every single piece of space junk and every Earth orbiting satellite would have two opportunities every day to damage or sever a space elevator.
The main purpose of a space elevator is not to act as a slingshot but to ease the difficulty* in lifting out of the deep part of a gravity well. For Earth, an elevator would also reduce or eliminate the energy lost to air resistance.
That a spacecraft could be lifted higher on the space elevator in order to gain more speed and reach, for instance, escape velocity, is a secondary consideration.
I am with LocalFluff on the need for space elevators for Phobos and Deimos. The surface gravity of these two moons is in millimeters per second per second and is not at all difficult for a spacecraft to overcome.
Larger asteroids, such as Ceres or Vesta, could benefit from space elevators, and a space elevator from the Moon to Earth-Moon L1 could be a tremendously useful asset. EML2 may also be a useful location, and in that case a space elevator to there would also be useful.
That is a creative use of the website field in your comment entry.
* Difficulty here means the great amount of propellant needed to lift out of the gravity well.
Edward, Okay I didn’t read your footnote. So you’re aware that LEO space debris is a major obstacle for an earth anchored elevator going to past geosynch. My bad for not reading all your post. I am often pressed for time and sometimes I quickly skim comments.
You also write “The main purpose of a space elevator is not to act as a slingshot but to ease the difficulty* in lifting out of the deep part of a gravity well.”
Phobos escape takes little propellant. I would hope this is very obvious. Once again, I am not talking about a parabolic escape orbit from Phobos gravity well.
A Phobos tether of 6155 km can fling payloads into hyperbolic orbit wrt to Mars. In fact this hyperbolic orbit has has a departure Vinf of 2.65 km/s, enough to hurl it to a perihelion 1 A.U. from the sun. In other words, in earth’s neighborhood.
Do really believe that the main consideration here is getting off Phobos’ surface? Insertion into an earth transfer orbit certainly is not a trivial thing.
An 8000 km Phobos tether can toss payloads to an aphelion in the Main Asteroid Belt.
A 5700 km tether descending from Phobos can drop payloads into Mars atmosphere at a speed of .6 km/s, about the speed of the Concorde jet. Entry, Descent and Landing would be far less difficult than entering Mars atmosphere at 6 km/s.
Hop David,
You asked: “Do really believe that the main consideration here is getting off Phobos’ surface? Insertion into an earth transfer orbit certainly is not a trivial thing.”
No, because a small rocket can do this very nicely. No one would need a space elevator for getting off the surface of Phobos or any other low-gravity body.
A secondary use of space elevators is to more easily accelerate payloads without the use of rockets or thrusters. This is what you are proposing, to fling or “slingshot” them into higher, lower, or interplanetary orbits. There are some difficulties that come with this use of space elevators, but they should be able to be overcome.
In the case of a cable or ribbon, as would necessarily have to be used at the Earth, Coriolis forces (and other perturbing factors) would cause the cable to swing, similar to a pendulum. This would be bad for stability, harder than necessary on the anchor point, but may assist in the slingshot effect you want to take advantage of, although it also could/would complicate the calculations for the orbit the payload would be inserted into. A stable elevator may be more desirable than a swinging one.
Phobos’ gravity is probably low enough that a structure, such as a kilometers-tall building or I beam (H beam?), may be able to be constructed. Such a large structure would act as a gigantic spring, which also may assist in the slingshot effect you desire. However, it may be more desirable for the structure to be self dampening so that the insertion orbit is more easily calculated or attained.
I also appreciate your proposed use of a space elevator to go from the Moon to EML1. When (or is it “if”?) EML1 becomes a busy place, such an elevator should be far more efficient than the rockets that ULA proposes in their Ciclunar-1000 video:
https://www.youtube.com/watch?v=uxftPmpt7aA (7 minutes, though you probably saw this soon after it was published)
In all cases, the space elevator may need some stations along its length in order to mount thrusters that would be needed to help control the elevator; a consideration for the reality of the elevator, even though you are currently concerned with the basics of finding uses for space elevators. A very long length of any material is going to act like a spring and like a pendulum, and these behaviors will complicate the actual operations. Even a solid structural elevator may have some behaviors of a tether, and that will have to be looked into, as we currently have little experience with tether behavior in orbit and across different orbital altitudes.
I like the concept of the space elevator, and I hope that we one day can use them at Earth, too, as they would avoid the “tyranny of the rocket equation” when getting men and materiel off the planet.
I hope you are talking to other space elevator enthusiasts in order to trade ideas, propose solutions to potential problems, develop the needed technologies, and test as many solutions as practical.
The advantage of having seven billion people coming up with their own problem-solving ideas over some governmental central committee coming up with all the ideas is that we potentially get seven billion more ideas that solve our problems.
In the case of a Phobos tether, flinging payloads isn’t the secondary use. Getting off Phobos is trivial. Flinging payloads towards earth or Ceres is not. Dropping payloads into Mars atmosphere at speeds lower than mach 2 isn’t trivial.
Yet you and Local Fluff continue using this argument. You seem to be saying “Let us ignore the fact that elevators can fling payloads at high velocities. So ignoring this obvious fact we can conclude getting off a body’s surface is the elevator’s primary use. And since getting off Phobos’ surface is trivial, a Phobos elevator isn’t worthwhile.”
So — No, the main purpose of a Phobos elevator would NOT be to lift payloads out of Phobos’ gravity well.
Yes, rising and descending payloads would exert Coriolis force which would induce oscillations. And these oscillations can also be damped by Coriolis force by timing the ascent or descent of payloads.
As you rise above Phobos on the elevator, centrifugal force increases and gravity diminishes. Descending below Phobos the opposite is true. This acceleration gradient keeps the tether aligned to the local vertical. See https://en.wikipedia.org/wiki/Gravity-gradient_stabilization
If a tether of more than 7 kilometers is extended past the Marsward or anti-Marsward ends of Phobos, the tension from the acceleration gradient is sufficient to hold them aloft. They would be towers held aloft by tension, much like an Earth elevator descending from geosynchronous orbit. But the stress is much less than what an earth elevator endures. So there’s no need to use bucky tubes or other exotic materials. Xylon would do fine.
A diagram of a Phobos anchored elevator is at the top of this page: http://hopsblog-hop.blogspot.com/2015/06/phobos-panama-canal-of-inner-solar.html
@Hop David
I enjoyed your appearance on the Space Show, hope to hear you on there again some day. I think I will have to re-listen to it after reading the discussion on this post.
If anyone else is interested, http://www.thespaceshow.com/show/19-feb-2016/broadcast-2649
Hop David
You wrote: “You seem to be saying ‘Let us ignore the fact that elevators can fling payloads at high velocities. So ignoring this obvious fact we can conclude getting off a body’s surface is the elevator’s primary use. And since getting off Phobos’ surface is trivial, a Phobos elevator isn’t worthwhile.’”
I wouldn’t say that it is not worthwhile, but it may not be worth the cost. Depending upon the solutions to many of the problems of space elevators that I rarely (if ever) hear advocates discuss, it may not be worth it. No one has looked into space elevators with enough research and development to know for certain. We won’t know all the problems and costs until we build and operate one, and we still need to study long tethers is space in order to discover and solve many problems before going to the expense of building the first space elevator. Hopefully, tethers will be studied soon. In the meantime, it is worthwhile to figure out various uses of elevators and calculate cost savings so that when the rest of the information becomes available, the costs can be compared and we can determine where they are worthwile.
The main advantage of the space elevator is that it transfers the energy source needed to accomplish a task from today’s costly* propellants to another source: the rotation of a large body, such as a planet or moon, and some energy source (electrical?) needed to climb and descend the elevator. The biggest problem that we have that needs solving is the difficulty (large propellant to payload ratio) in getting off the Earth. Tsiolkovsky may not have thought of the idea if he hadn’t realized that the rocket equation is such a [*ahem*] for getting off the Earth.
You wrote: “Yes, rising and descending payloads would exert Coriolis force which would induce oscillations. And these oscillations can also be damped by Coriolis force by timing the ascent or descent of payloads.”
I keep hearing this, but it does not hold up. The payload gets released and only the forces induced by the descending climber is left to dampen the oscillations. Even under the best of circumstances, propellant will still have to be expended in order to complete the stabilization of the elevator, just due to the Coriolis forces.
Keep in mind that there is the gravity gradient of Mars to contend with. This is yet another (variable) force that will contribute to instability. There are long-term effects of the sun’s constant gravitational tug on the elevator, too.
The base of the elevator will have to be carefully designed, too, as the forces on the elevator will transmit to the base anchor point. This is not as much of a problem for a tether, but a tower is a cantilever and will have not only the small shear forces but also tremendous bending moments at its base, and this will have to be considered in the design. Each newton of force at one kilometer altitude imparts a bending moment of one thousand newton meters. This happens along the length of the tower, so that same newton of force at a seven kilometer altitude imparts that one thousand newton meter bending moment at the six kilometer altitude, and it is two thousand at the five kilometer altitude, and so forth.
Pinning the base so that it rotates in two degrees of freedom reduces this problem but will leave you with a structure that behaves somewhat similar to a tether, meaning that much of the spring effects are lost, as well as some of the dampening that comes with the construction material used for the stiffer geometry.
Watch out for vibrations and natural frequencies, too. They make nice music from violins and sitars, but they can do nasty things to structures and payloads.
Choose your materials carefully. They have to stand up to long exposures to the space environment. These include not just vacuum (e.g. potential loss of material strength due to outgassing) but radiation (e.g. age hardening of some materials), ultraviolet light (e.g. degradation of many plastics), and other hazards.
* Cost is not just the per-pound price tag but includes rocket engines and solutions to the associated problems — such as rockets exploding while sitting on the pad.
Edward writes “I wouldn’t say that it is not worthwhile, but it may not be worth the cost. Depending upon the solutions to many of the problems of space elevators that I rarely (if ever) hear advocates discuss, it may not be worth it. ”
I talk about space debris, through put, mass requirements of the tether and other problems on my blog. If you’ve never seen this advocate discuss it, it is because you haven’t bothered to read my blog. And of course it may not be worth it. Just about all schemes to settle and exploit the solar system are speculative. This goes without saying. I thank you for stating the obvious.
But you still haven’t addressed my objection to your earlier argument. You matter of factly state an elevator’s main purpose is to get payloads out of a body’s gravity well. Which is obviously false if we’re talking about a small body like Phobos or Deimos.
Edward writes “I keep hearing this, but it does not hold up. The payload gets released and only the forces induced by the descending climber is left to dampen the oscillations.”
An ascending elevator car exerts a westward Coriolis force. A descending car pushes the tether to the east.
If your elevator car needs to ascend, just wait till the oscillation is pushing the local tether to the east. Then the westward Coriolis force will damp the motion. When the wave moves on, stop the ascent and resume when the next crest arrives.
If your car needs to descend, you wait until the oscillation is pushing the local tether to the west.
I say a westward push can dampen a push to east. Please explain how this doesn’t hold up.
Edward writes: “Keep in mind that there is the gravity gradient of Mars to contend with.”
It is mostly the gravity gradient of Mars that keeps a Phobos anchored tether aligned to the local vertical. There’s also the so-called centrifugal force maintaining tension and keeping the tether aligned to the local vertical.
“There are long-term effects of the sun’s constant gravitational tug on the elevator, too.”
Sure. But witness the many moons that remain tide-locked to their planets even with the sun’s influence. Phobos and Deimos are two such moons. With a vertical gravity gradient stabilized tether, Mars’ tidal stabilization is even stronger.
Edward writes “The base of the elevator will have to be carefully designed, too, as the forces on the elevator will transmit to the base anchor point. This is not as much of a problem for a tether, but a tower is a cantilever”
Most of my posts talk about Zylon tethers. Why are you talking about towers? Have you bothered to read my posts?
Hop David,
You wrote: “I talk about space debris, through put, mass requirements of the tether and other problems on my blog. If you’ve never seen this advocate discuss it, it is because you haven’t bothered to read my blog.”
And now you can discuss stability, Coriolis forces (outside of Footballs and naval battles), stability, bending moments, base anchor points (especially for towers), and perturbations due to gravitational forces. They are advanced topics, because the space debris, throughput, and mass and counterweight discussions are basic to the usefulness of the tether. They give basic knowledge of whether a space elevator should even be considered for the task discussed.
Additional considerations need to be discussed to be sure that the construction and operation are practical or even practicable. It is one thing to say that you will build a railroad across a continent or across an ocean, but it is a different thing to actually do it and operate it. Transcontinental railroads are practical, but so far there no transoceanic railroads.
You wrote: “This goes without saying. I thank you for stating the obvious.”
You are welcome. Sometimes it needs to be said, because no one is considering it.
You wrote: “ You matter of factly state an elevator’s main purpose is to get payloads out of a body’s gravity well. Which is obviously false if we’re talking about a small body like Phobos or Deimos.”
Big “if.” I was under the impression that I addressed this “if” condition.
You wrote: “An ascending elevator car exerts a westward Coriolis force. A descending car pushes the tether to the east.”
Ah! Now I understand why space elevator advocates miss the obvious, which often needs to be stated. If only we had a few more engineers and scientists working on these problems … .
As the climber/car/wagon descends the elevator, the eastward forces are less than the westward forces imparted by the climber plus the payload. The forces do not balance and no matter the timing, you will not return to stability without additional corrective measures.
You wrote: “It is mostly the gravity gradient of Mars that keeps a Phobos anchored tether aligned to the local vertical. There’s also the so-called centrifugal force maintaining tension and keeping the tether aligned to the local vertical.”
Here is a nice experiment for you. Simulate a tethered elevator by swinging a weight on a string around your head. I recommend a rubber eraser for the weight. Start with a string length of one foot, and eventually let out more length until you reach a meter in length. Continue letting out string until you reach five meters or as long as you can get before the tether strikes the ground. Notice that the longer the string gets, the less straight it is. This is the instability in this tether experiment. Planetary tethers will have additional instabilities to overcome.
P. K. Aravind’s paper, “The physics of the space elevator” does not include gravitational bodies other than the one the elevator is anchored to. Your analysis is nice to the first order, but there are several other considerations that reality will impose upon the space elevator.
http://hopsblog-hop.blogspot.com/2013/02/golden-tethers.html
The gravity gradient stabilized tether may not be as stable as you think, even without the Coriolis forces of a climber and payload. A tether is not stiff enough to act as one body, and any small perturbation is going to have quite an effect on the assumed stability. Just as with the ISS, a payload that is expecting to dock or berth with a gravity gradient stabilized tether will expect it to be right where it is expected to be, not a few meters/kilometers away, because of unaccounted for perturbations. Unlike the ISS, neither the tether’s end nor the rendezvousing payload will be in an actual orbit, so they will not have much time to link up before the payload falls away.
A rotating tether (the Rotovator was the initial link to your site) that moves payloads between orbits will be rotating through a gravity gradient, and Aravind’s paper does not cover this condition. He only covers a stable, vertical elevator with only the anchor-planet as the sole source of gravitational/perturbational influence.
You wrote: “Sure. But witness the many moons that remain tide-locked to their planets even with the sun’s influence.”
You are now comparing solid, very stiff moons to a wibbly wobbly string tether. Even a tower will be a very long spring and will be subject to many forces that will try to take it out of a straight or vertical orientation. Please notice that no matter how tidally locked Phobos is, its orbital eccentricity makes a perfectly straight, stable tether swing back and forth relative to the gravitational center of Mars. It may not seem to be much, but it moves the catch-and-release end of the tether as seen from the Martian surface. Any tidal stabilization imparted by Mars will in reality provide an instability to the tether, as the gravitational center will pull the tether in different directions relative to Phobos, as Phobos orbits around Mars.
You wrote: “Why are you talking about towers?”
I suppose it is because of your comment: “If a tether of more than 7 kilometers is extended past the Marsward or anti-Marsward ends of Phobos, the tension from the acceleration gradient is sufficient to hold them aloft. They would be towers held aloft by tension, much like an Earth elevator descending from geosynchronous orbit.” [emphasis on the word “tower” is mine.]
Towers have a distinct meaning from tethers and distinct from monoliths. Even a space elevator tower would be held aloft by tension.
However, my part of the discussion is apparently more general than yours. I expect that there are others reading these comments, and they deserve a little broader education about space elevators than just a very narrow discussion would present.
How does Zylon hold up under the conditions of space environments? My understanding is that it degrades under ultraviolet light. Just because Eubanks and Laine have suggested the use of Zylon does not mean that they have adequately researched it.
You wrote: “Have you bothered to read my posts?”
There are quite a few, but I have looked over the ones that you linked to, and I have searched your site to see whether you were discussing some of the topics that I brought up (e.g. stability, perturbations, etc.). So far, you do not appear to be doing so.
Your site demonstrates that there are some very interesting locations that may be well served by space elevators, and that there are some interesting possibilities for other forms of tethers. Whether they can be made to be practical remains to be seen. I hope that at least some of them can be.
Edward, you write “Towers have a distinct meaning from tethers and distinct from monoliths.”
Do you think the term tower implies a rigid cantilever? If so, you are obviously unfamiliar with the literature. Arthur C. Clarke’s book Fountains of Paradise uses the word tower for flexible, tensile structures. As does Jerome Pearson
But even if you hadn’t seen the term in literature, you should have been able to deduce from context I have been talking about flexible, tensile structure.
Edward, you write “Ah! Now I understand why space elevator advocates miss the obvious, which often needs to be stated. If only we had a few more engineers and scientists working on these problems … .”
If you bother to read the literature you would find space elevator advocates have worked on problems such as Coriolis. And of some of these advocates are talented engineers. From the Pearson paper I linked to earlier discusses the notion of critical velocity:
One other dynamic problem is the excitation of traveling waves along the tower
by the transverse forces of payloads ascending the tower, analogous to the whipping
of overhead electrical wires caused by the pantograph of a fast electric locomotive.
There are critical velocities for which large oscillations would occur, corresponding
to the velocities at which the payload would travel twice the length of the tower
during one complete period of a lateral vibration mode (Timoshenko, 1941).
Pearson recommends that elevator cars avoid traveling a critical velocity for long periods of time.
Depending on the velocity of the payload, the Coriolis push can reinforce the wave or damp it. Whether the elevator car is descending or ascending, whether it is empty or full of payload, it is possible to damp waves by timing the travel of the car.
Edward, you write: “Here is a nice experiment for you. Simulate a tethered elevator by swinging a weight on a string around your head. I recommend a rubber eraser for the weight. Start with a string length of one foot, and eventually let out more length until you reach a meter in length. Continue letting out string until you reach five meters or as long as you can get before the tether strikes the ground. Notice that the longer the string gets, the less straight it is. This is the instability in this tether experiment. Planetary tethers will have additional instabilities to overcome.”
Go to Google Images and search for Carnival Ride Swing. You will see your scenario in action and so far as I can see, the chains are straight.
Moreover, that is a horrible model of the vertical space tethers. In gravity gradient stabilized tethers, gravity pulls towards the center of the planet and centrifugal force pulls the opposite direction. In your scenario, the gravity acceleration vector is at right angles to the the centrifugal acceleration vector.
And there is more wrong with your model. Speed of any point on the tether is ωr where ω is angular velocity in radians and r is the point’s distance from axis of rotation. It is obvious V scales with r. And wind drag scales with V^3. So you have another substantial force acting on your model that would not be found in the vacuum of space.
Edward you write “Big ‘if.’ I was under the impression that I addressed this ‘if’ condition.”
Were you under the impression you had made a strong case against a Phobos anchored tether? You have not. After reading your arguments I still hold the opinion that Phobos is one of the most plausible and beneficial places to anchor an elevator.
Hop David,
You wrote: “But even if you hadn’t seen the term in literature, you should have been able to deduce from context I have been talking about flexible, tensile structure.”
At those lengths, they most certainly will not hold up to compression forces. They cannot possibly have the column strength to do so. No matter how rigidly they are made, at those lengths they will be very flexible, indeed, which is what my comments are about.
And yes, a space elevator could conceivably be constructed as a cantilevered tower. Whether this is practical even on Phobos, I do not know. Once again, these are more generalized comments than any individual post on your site.
“Pearson recommends that elevator cars avoid traveling a critical velocity for long periods of time.”
Which does not address the problem being discussed. If you are going to change the topic every time we correspond, then 1) this is going to be a very, very long discussion, and 2) we aren’t going to make any headway at all. I’ve done these types of unproductive discussions before, but I intended for this discussion to be serious, not a pissing match.
“Go to Google Images …”
Not the same experiment, not the same construction. Do not expect the same results. This is another example of changing the topic.
“Moreover, that is a horrible model”
Well, so is the carnival ride swing. I proposed an experiment that we can make without too much work.
“So you have another substantial force acting on your model”
Other substantial forces is the whole point of the exercise.
“Were you under the impression you had made a strong case against a Phobos anchored tether?”
I don’t know what I wrote to give you this impression. In fact, I have attempted to be encouraging. Please do not take the pointing out of a couple of inadequately explored factors and the suggestion that propellants may have to be used to overcome some of them as even remotely like a case against any one of the ideas you have discussed on your site.
The intention was not for you to get defensive but to explore additional factors that have not yet been adequately explored. It is like trying to navigate the solar system while only solving two-body orbital mechanics mathematics and ignoring the practical realities of space travel.
The final arbiter of whether any or all of the ideas on your site are practical or worthwhile will come as tethers are explored and tested on orbit and as space elevators are constructed in various places.
Even railroads started out small and grew in size, distance, and capabilities as they were explored, developed, and operated and their limitations realized or overcome. I expect space elevators and space tethers to have similar beginnings, but it would be nice to explore and better understand all the factors before spending the resources to make the first one only to have it fail due to an unexpected but foreseeable problem.
I am disappointed at how little tethers have been tested, so far, leaving us with knowledge of their behaviors that is inadequate to make solid designs and plans for their use. Instead, we are left with hypotheses and mathematical models, rather than practical models based upon experience.
I have presented some factors for you to contemplate. Ponder them or don’t; I no longer care.
Edward you write “Which does not address the problem being discussed.”
Your rambling walls of text split into many branches. Most of them are irrelevant to what I’ve been talking about but a few are of interest.
Coriolis force inducing oscillations is one of the few relevant topics you’ve brought up. And Pearson most certainly does address that problem. Coriolis force can induce oscillations if the elevator car is moving the critical speed. And Coriolis force can also be used to damp oscillations.
Edward, you write “If you are going to change the topic every time we correspond, then”
You are the one inflating your walls of text with new topics. The structures I have been discussing are tethers made of flexible Zylon held aloft by tension. So why do you point out the problems with rigid cantilever towers? I have little time and it annoys me to waste it reading your irrelevant straw men.
Edward, you write “Other substantial forces is the whole point of the exercise.”
Atmospheric drag is the substantial force I object to in your model. Atmospheric drag doesn’t exist in a vacuum.
And if you want to talk about gravity and centrifugal force, the model is also wrong. Acceleration vectors at right angles to one another are not the same as vectors anti-parallel to one another.
Edward, in you write “I don’t know what I wrote to give you this impression.”
Here is what you wrote December 3, 2016 at 5:33 pm:
The main purpose of a space elevator is not to act as a slingshot but to ease the difficulty* in lifting out of the deep part of a gravity well.
And since it’s easy to get out of the deep part of Phobos’ gravity well, you and Local Fluff assert a Phobos elevator is of little use.
Well, getting out of the deep part of a body’s gravity well isn’t an elevator’s only possible use. An elevator can also be used to impart delta V. It can be used as a sling as well as a lift.
In the case of a small body like a Martian moon or an asteroid, getting out of the tiny body’s gravity well would certainly not be the main use.
This is exactly the kind of pissing match that I wanted to avoid. Instead of a productive discussion, you continue to be defensive to the point of blaming me for your mention of towers, griping that I don’t include possible secondary uses as part of the main use of a space elevator, and mischaracterize what I and others have said about a space elevator on Phobos — worse, correcting your mischaracterizations has proved futile.
The discussion of space elevators was started by me and I expected that you were commenting on that discussion, but you seem to insist on redirecting the discussion such that the only discussion allowed is of those referenced on your blog, with a further limit that only a Phobos elevator may be discussed. Which Phobos elevator is not clear.
Not only do I no longer care whether you ponder the topics I posed, I no longer care to waste my time reading your unproductive comments. You have been a great disappointment.
I hope you continue to do better than this attitude on your own site. The posts that I saw seemed worth reading.