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Lesson 3: Archive Notes February 17, 2010

Posted by drspaceshow in Uncategorized.
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Space Show Classroom Lesson 3:  Orbital/Flight Dynamics

Tuesday, Feb. 16, 2010 

Archive Notes and Program Information

The Space Show Classroom Lesson 3 Orbital/Flight Dynamics  can be downloaded or heard at:

 http://archived.thespaceshow.com/shows/1308-BWB-2010-02-16.mp3

Guests:   CLASROOM:  Dan Adamo, Dr. John Jurist, Dr. Jim Logan:  Topics:  Lesson 3:  Orbital/Flight Dynamics.   Lesson 3 for The Space Show Classroom featured panel members Dan Adamo, Dr. John Jurist, Dr. Jim Logan, and myself to discuss the basics of orbital and flight dynamics.  As with all Classroom programs, the goal is to ground listeners in reality on the basics of space flight.  This two hour plus program consisted of two segments, about an hour each. In our initial segment, we asked Dan Adamo to provide us with a basic understanding of both orbital and flight dynamics and what a Flight Dynamics Officer (FDO pronounced as Fido) actually does.  We also talked about the training required, the supervision, internships, computers used and the various positions available including working the console.  Dan also explained the difference in doing an LEO mission versus a longer mission to the Moon, a NEO, or Mars. He also described the differences in working a human spaceflight mission versus a science or robotic mission.  At one point, I asked Dan to extrapolate to the needs of orbital space tourism or an orbital destination to a Bigelow space station.  Listen carefully to what Dan had to say about the flight dynamic for this type of private mission as compared to a Shuttle mission.  We talked about what happens with an orbit and its  planning with variable ISP such as VASIMIR technology.  We started the description and explanation of transfer orbits using the Moon as an example.  This is a very important factual discussion including rendezvous, the concept of antipode, and launch windows.  Here, our panelists explained that we launch eastward but to go to ISS at 51.6 North, we have to go to the NE. The penalty for doing this was clearly and technically explained.  This discussion brought up staging and the tyranny of the rocket equation.  Pay attention to the required maneuvering to get to station, why it starts almost immediately after leaving the pad, and the penalty paid by Europeans and even the Russians to get to this orbit.  As you will hear, once at the ISS, its easy to go to the Moon and other places, but getting to ISS does involve a costly launch penalty.  I asked about polar orbits to the Moon and our panel members explained the facts of this type of orbital action in detail.  The timing and windows on the polar orbit are far more severe than equatorial or an ISS launch.  In our second segment, our guests said that the reason orbital dynamics was so hard was because of the tyranny of the rocket equation.  Don’t miss this discussion.  They also said its the reason why startups trying to solve these problems are always strapped for cash.  Chemical rockets just don’t do all that well.  Dan then talked about Adamos Rules for the Road for Gravitational Harmony (ARRGH).  These rules are on the blog as part of the Lesson 3 presentation materials.  Pay close attention to what these rules mean and how they are applied to real life situations.  Our panel then entered into a comprehensive discussion regarding orbital propellant depots.  This is an essential and must hear part of this Classroom program as we talked about orbital dynamics issues, propellant depot orbits and locations including at the destination, cryogenic transfer, location near the ISS and much more.  We also talked about plausible and not so plausible propellant depot missions.  Here, Dan said those proposing propellant depots need to undertake a Conceptual Mission Design and run the numbers.  Orbital and flight dynamics need to be part of the analysis, not just the engineering issues.  We then talked about the presentation material submitted by Dr. Jurist and partial orbits, launch east instead of west and Jim brought up the concept of minimum energy used by the clipper ships as an analogy to why launching east is more effective than Point to Point going west.  As we concluded this segment, our panel members said the purpose for the Classroom was to offer grounding to people on the basics of the issues controlling spaceflight.  Jim suggested that the future is not unfolding as any of us thought it would be and this presents us with disconnects from facts and reality.  Dr. Logan suggested four areas that we must all be grounded in:  1) the rocket equation; 2) flight dynamic; 3) bio-medical and human factors realities for space travel; 4) propulsion.  He said to solve these much needed problems, grounding is essential.  All of us agreed.  If you have comments or questions, please post them on The Space Show Classroom blog at https://spaceshowclassroom.wordpress.com under the Lesson 3 Archive section.  All co-host email addresses are on the blog and Dan Adamo said he could be reached at adamod@earthlink.net.  All notes and comments sent to me at drspace@thespaceshow.com will be posted on the blog.

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Comments»

1. drspaceshow - February 17, 2010

During Lesson 3, a listener inquired about software or online services for orbital and related software. Listener Theron offered these two suggestions:

1. Perdict is one program that can do some orbital prediction and caclulation. http://www.qsl.net/kd2bd/predict.html.

2. This is JBSim it will produce very detailed results if given a full vehicle profile. http://www.jbsim.com.

Thanks to Theron for this information.

David

2. Tom Hanson - February 19, 2010

Thanks for this terrific series. Lesson 3, with discussion of orbital planes, reminded me that modern gaming software is capable of amazing visual effects. It should be possible to create video that allows the user to change the point of view of the Earth showing one or more orbital planes. That would be helpful for people (like me)! Here is a URL to a 3D package that appears to be available to members of the IEEE. It runs on Matlab.

http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F5072598%2F5072599%2F05073232.pdf%3Farnumber%3D5073232&authDecision=-203

It would be interesting to know if NASA already has 3D modeling packages that are available to the public, and we just don’t know about them?

(th) Columbus

3. Dan Adamo - February 20, 2010

Over the last several years, I’ve been making use of open-source planetarium software called “Celestia” as a means of visualizing space trajectories in 3D. Any trajectory I design can be exported to Celestia, portrayed with an extensive database of solar system objects, and viewed from any location. These “flights of fancy” can also be scripted into very effective presentations. You can download Celestia free of charge from http://www.shatters.net/celestia as a standalone app for Windows, Mac, and Linux PCs. I’m particularly interested in assisting educators who want to simulate customized student-run space simulations with Celestia.

4. drspaceshow - March 23, 2010

This is a note from Joe Evans of Houston which was sent to me and I am posting it to this blog. David

From Joe:
I thoroughly enjoyed this presentation by all participants. I could actually see your souls. I am intimately familiar with the rocket equation, powered explicit guidance, gravity losses to delta v, high fidelity simulations, and all of the other wacko terms used that causes the average person to suffer brain aneurisms.

The debate on whether on-orbit depots are feasible was really interesting and thought provoking. Many unanswered and vitally important questions still remain. Understandably, there is visible resistance to the concept of on-orbit fuel depots. I call this behavior “Thrashing”. Thrashing is a healthy term used to challenge the people who can make a difference early in the development process. If performed early, before the concrete dries, the later development stages will go smoothly. If performed late, the later development stages could easily stall and fail. Constellation is an example of what happens when thrashing occurs late in the development stage. I strongly believe this concept of on-orbit fuel depots will never die no matter how much people try to convince others of the physics and difficult logistics involved. This concept begs an experiment. It almost happened for Constellation, however, NASA refused to redesign their vehicles to receive on-orbit fuel since it appeared too late in the development stages.

Putting a fuel depot in the same orbital plane as the ISS does not necessarily increase traffic to and from the ISS and therefore disrupt zero-g experiments. It stabilizes the logistical traffic to and from the ISS. The ISS is already up to their eyeballs in a constant stream of vehicles docking and undocking. This was one of the main arguments Dan had against it. I highly respect his opinion since I come from a similar career background. I believe having one in the same orbital plane could increase the number of competitive launch services to low earth orbit. Lowering the cost to access low earth orbit is the challenge our President has made. If commercial enterprises don’t respond, the Russians, Japanese, Europeans, and probably the Chinese will. There are plenty of space fairing entities capable of responding.

By 2025, the ISS’s legacy is not going to be what they discover in zero-g but rather what they discover when they address the problem of vertebrate animal bone loss using existing onboard centrifuges, i.e., figuring out the minimum dosage of intermittent gravity exposure to take with them when people go to Mars. The other side of the coin, i.e., the radiation problem will be equivalently difficult but not impossible to overcome. I wish there is a way I could create a convincing and practical solution to this problem but my energies are focused on the bone loss problem. People exist that are much more capable and focused than I am in addressing this problem. It is just a matter of finding them and getting them engaged.

Thanks for all that you do.

Joe Evans
Houston

5. Tom Hill - August 4, 2010

Late to the party, I know, but I’ve been in contact with Dan about weather constraints for launches to propellant depots, and also to get more information about how the orbital elements of the depot affects beyond-LEO departure delta-vs for a particular target.

So far, my research on launch windows and weather constraints brought me to an AIAA document (AIAA-1995-55 Aerospace Sciences Meeting and Exhibit, 33rd, Reno, NV, Jan 9-12, 1995) where the authors analyzed the shuttle’s capability to reliably reach the space station during construction. Using weather data at Kennedy Space Center from 1957 through 1991 and a set of shuttle-based launch constraints (including return to launch site criteria), they determined that it takes anywhere from two (many times throughout the year) to eight (if you want to launch in September at 1400 ET) launch attempts to achieve a 98.3% chance of launching.

The goal of the paper was to find out how many launch attempts it would take to achieve 95% confidence including vehicle uncertainties. Adding the shuttle’s chance of making a particular launch at that time (assumed to be 57.2% for the study), the number of attempts varied from 6 to 12.

Based on my recollections, the number of launch attempts to reach the station have been significantly lower than those numbers.

6. Jim Logan - August 5, 2010

Tom,
Very interesting post! Thank you very much.
I was with you until your last statement – – not because I disagree but because I haven’t been able to get my hands on these data!
If ANYONE knows where launch attempt records are documented and/or archived, PLEASE let me know.
What I’ve been trying to get a handle on for years is this: what percent of the time has the shuttle actually launched on the first (i.e. original) scheduled date? I suspect the percent is disappointingly low. Of course there are multiple reasons why launches are ‘pushed back’ or ‘scrubbed’ (weather constraints are only one possible reason). However, launch windows, per se, shouldn’t be. I assume ‘original’ launch dates are selected in large part because they met specific launch window criteria (Dan Adamo might be able to enlighten us on this one).
Only when we know the REAL stats (e.g. how many times have shuttle launches been pushed back or scrubbed, what has been the average number of launch attempts [all total for any reason] required per mission regardless of whether the destination was the ISS or not?) can we then tease out the various reasons.
Until we get actual numbers (i.e. evidence!), I will have to question your assertion that “based on my recollections, the number of launch attempts to reach the station have been significantly lower than those [AIAA 1995 study] numbers.” My own personal recollection (which doesn’t substitute for evidence) leads me to believe it has definitely been within the predicted AIAA 1995 range.
Many thanks for your insights and your contributions to the blog!
Jim Logan

7. Tom Hill - August 5, 2010

I’m new to this idea of ‘academic blogging’, and Dan had similar problems with my last statement. Lesson learned.

Part of the problem is that launch dates aren’t set until most people are relatively sure they’ll be able to launch on that date. It’s last minute things that crop up and cause the problem. STS-125 is an example where launch processing was pretty far along when suddenly a failure on Hubble forced a stand-down for months while a new system was readied for repair.

In response to Dan’s concern expressed to me over email, I took a couple moments and looked at Wikipedia entries (http://en.wikipedia.org/wiki/STS-YYY, where YYY= the mission number. All associated caveats for using Wikipedia apply, but until someone has a better source of data…) for all the shuttle missions starting with return to flight after Columbia. Here’s how they stacked up:

According to Wikipedia, the following missions flew on their first attempt:
STS-132,131,129,126,124,123,120,118,117, and 121
The following flew on their 2nd attempt:
STS-130 (wx delay), 119 (tech delay), 116, (wx delay)
Two went on their third attempt:
STS-128 (1 wx delay, 1 tech), STS-122 (2 tech delays)
And one went on its sixth attempt:
STS-127 (3 wx delays, 2 tech)

This data can be looked at a few different ways. From one point of view, 10 out of 16 launches went on their first attempt. It can also be viewed that only 16 out of 28 launch attempts actually fly. Since my original point was that, to my recollection, it took fewer than 6-12 launch attempts to make it to the space station, I feel the first read is the more pertinent to this discussion.

By the by, the record for most launch attempts before launch is 6, a tie between STS-61C and STS-73 (http://www.space.com/missionlaunches/090713-sts127-delay-record.html). So none have approached the 12 attempts statistically described in the paper. Ironically, neither of these missions were to a space station. I haven’t found any mention of their launch windows, whether they were as short as a space station mission launch window.

I’d emailed this information to Dan (except for the part about launch attempt records), asking if he had better information, but decided to post it in response to your blog comment.

8. Tom Hill - August 17, 2010

I just found Dan’s video of the outbound leg of a mission to 1999 AO10:

I noted that 1999 AO10 is one of the asteroids mentioned as a candidate for human exploration at the NEO conference:

http://www.nasa.gov/pdf/474223main_Johnson_ExploreNOW.pdf

I was planning on doing my depot study using one of these asteroids, but Dan’s work makes the choice much easier. Would Dan please email me (or post here) the specifics of the parking and departure orbits?

9. Trent Waddington - August 17, 2010

Listeners and hosts may find a webapp I recently wrote interesting:

http://quantumg.net/asteroids/skymap.html
http://quantumg.net/asteroids/help.html

It’s a webapp for displaying Earth-centric plots of asteroids. I recommend using the Firefox web browser to access it, although I’ve heard that Chrome and Opera also work. I’ve heard that IE7/8 do *not* work and most likely never will, and I haven’t heard if Safari works.

Dan Adamo - August 23, 2010

Glad you had a look at the 1999 AO10 video, Tom. I’d like to add a sound track someday, but it’s reasonably immersive already if you select 720p HD resolution and full screen mode. After post-Constellation deep space vehicle designs become evident, I’m hoping some enterprising CAD/CAM expert will help me replace the Apollo CSM rendering with something more realistic. All Celestia needs is the appropriate .3ds files.

As for your data request, I suspect you’re opening a bigger can of worms than you realize. The launch season from Earth to 1999 AO10 in 2025 spans several weeks. During this time, the Earth departure asymptote to 1999 AO10 will likely track across tens of degrees in geocentric right ascension and declination. To assess your propellant depot concept’s ability to cope with launch and Earth departure delays would therefore require a dozen or more trajectory solutions spanning the season. With my current obligations, I’ll have to leave this task to you.

Tom Hill - August 24, 2010

Soundtrack would be cool, but I agree that it’s pretty engaging as is. I did watch it at 720p so I could read the notes. I was going to comment on the Apollo CSM usage, but figured it wouldn’t be a popular comment. Sort of like a Doc Brown “It’s not to scale and I didn’t have time to paint it”

I’m assuming Celestia doesn’t do window calculations, just propagates orbits that you enter. Is that correct?

For the data request, I understand about shifting windows, but the scenario you used would make a good starting point. I don’t want to cause you extra work, but my software capabilities don’t include a solar system astrogator at this time, just Earth orbit. May I have the orbital elements and reference frame of your parking orbit, the delta-v applied for TNI, and the sun-centered orbital elements and reference frame of the outbound leg, both pre- and post- the 2.2 km/sec maneuver done near AO10? I’ll see what I can do with those.


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