jump to navigation

Dr. John Jurist Webinar, Sunday, 4-26-15 April 25, 2015

Posted by The Space Show in Uncategorized.
Tags: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,
trackback

                Dr. John Jurist Webinar, Sunday, 4-26-15

Selecting The Rocket Motor, Fuel, & Trade To Optimize The Mission

http://archived.thespaceshow.com/shows/2461-BWB-2015-04-26.mp3- audio

https://vimeo.com/126223310– Webinar video

Your Amazon Purchases Helps Support TSS/OGLF (see www.onegiantleapfoundation.org/amazon.htm)

If you rate shows on live365.com, email me your rating reasons to help improve the show

Guest:  Dr. John Jurist.  Topics:  Choices and consideration in configuring launch systems.  Please direct all comments and questions regarding Space Show programs/guest(s) to the Space Show blog, https://thespaceshow.wordpress.com.  Comments and questions should be relevant to the specific Space Show program. Written Transcripts of Space Show programs are a violation of our copyright and are not permitted without prior written consent, even if for your own use. We do not permit the commercial use of Space Show programs or any part thereof, nor do we permit editing, YouTube clips, or clips placed on other private channels & websites. Space Show programs can be quoted, but the quote must be cited or referenced using the proper citation format. Contact The Space Show for further information. In addition, please remember that your Amazon purchases can help support The Space Show/OGLF. See www.onegiantleapfoundation.org/amazon.htm.  For those listening to archives using live365.com and rating the programs, please email me as to why you assign a specific rating to the show. This will help me bring better programming to the audience.

 

Welcome to this two hour webinar regarding the choices and considerations that can be made in designing and configuring launch systems.  TO VIEW THE WEBINAR VERSION OFTHIS PROGRAM, GO TO https://vimeo.com/126223310.   Note that on the blog for this program are two Power Point presentations for your use.  Dr. Jurist referred to both of them during the webinar, especially the presentation titled “Choices: Some Considerations in Configuring Launch Systems.”  I urge you to follow along with them during the webinar.  During the first segment, Dr. Jurist explained the target market for the webinar and his two presentations.  He then talked about how hard it was to go to Mars and do other missions.  Then he got to the point by saying in designing or configuring the launch system for a mission, you started with the payload requirements which then provide additional constraints once the payload has been defined.  He also talked about the application of the basic rocket equation and explained the importance of exhaust velocity, the Delta-v, and the mass ratio.  Listeners started asking questions so two stage compared to single stage was discussed.  John pointed to the Choices presentation, slide 8.  He talked about propellant and pressures, both in a pressure fed system and with a turbo pump system.  Another listener asked about solids versus liquids, then Marshall called to talk about rocket g forces.  Dr. Jurist talked about designing the rocket envelope environment to the payload specifications.  He then brought in and discussed the vibration envelope.  Helen asked how things would be different with a human payload rather than a satellite or cargo.  Reliability was a big concern.  Near the end of the segment, Dr. Jurist talked about payload mass in Leo and BLEO.  Doug inquired about the gravity loss during the launch, then the segment ended talking about heavy lift, solids and proportional cost factors for SRBs.

 

In the second segment,  Penny asked how the variable that had been discussed would change were one launch from the Moon or Mars.  Adrian emailed in about the NERVA rocket and nuclear propulsion.  Dr. Jurist used the German V2 as an example of launching from the Moon.  Specific impulse and exhaust velocity came up again, then the focus turned to rocket motor cooling systems.  Questions continued coming in asking about 3D printing of rocket motor parts to lower the cost and the use of hybrid rocket fuels with their advantages and disadvantages.  Regulatory issues came up in this segment as did political issues, plus our guest got a question about amateur rocketry.  A listener asked about environmental concerns over rocket fuel . Dr. Jurist directed the audience to the Choice presentation, slide 22, and talked about ways to possibly shed some weight such as dumping the payload shroud.  Near the end, John got questions about the Falcon Heavy, Doug called in with questions about lunar lander economics and more.  In closing, Dr. Jurist said “the fundamental theme of the presentation was the many variables that come into play in designing or configuring a space launch system, how the many variables are inter-related, and how every decision in the process constrains or narrows the remaining options.”

 

Please post your comments/questions on The Space Show blog above.  You can contact Dr. Jurist through me.

                                                       Choices

                                   Launch Vehicle Business Workshop

Comments»

1. Ken Lundermann - June 25, 2015

I enjoyed this informative show — thanks a lot!

One minor point I’d make. It was suggested at one point that larger liquid engines tend to be more efficient in that they produce more thrust for a given weight. I believe it actually tends to go the other way: smaller engines (at least over some size range) actually do better.

Imagine we have an engine of a given thrust and now we need four times more thrust. We could use four engines, or we could use one larger engine. If we’re going to operate the larger engine on the same propellants at the same pressure, we’ll need four times the propellant flow and hence four times the injector area. Assuming we keep the same length of comubstion chamber (which should be possible to a first approximation), the chamber will quadruple in mass. So far, this is consistent with keeping ratio of thrust to weight about the same.

But now, consider the nozzle. If it is to quadruple its throat area while keeping the same shape, it will have to double in length. To a first approximation, its mass will increase by a factor of eight, tending to *decrease* the thrust to weight ratio of the larger engine as compared to four smaller engines.

Other factors may be relevant — such as the more complicated plumbing we’ll need for four engines, and the larger combustion chamber may be slightly more efficient — but there is reason to expect larger engines to be a little heavier for their thrust than lighter engines.

2. ericmachmer - May 6, 2015

Thanks you very much John for presenting such an informative thorough lecture. Since you mentioned addressing topics raised by callers in a future show could I suggest a few as late questions, perhaps for consideration in a future show?

I’m curious about the configuration of Blue Origin’s rocket and their choice of a hydrogen rather than methane engine (like the Falcon 9). Can a hydrogen oxygen engine be throttled for reusability/landing? Does it operate at different temperatures/pressures than a methane engine – would this affect reusability…up to the thousand times Musk expects to recycle each Falcon? Are fuel costs similar? If the primary/sole objective is simply to place mass in LEO what is the advantage of hydrogen over methane? Or hydrogen over clusters of methane engines, such as with the Falcon Heavy? Space X speaks of the utility of a methane engine for Mars landing/refueling/takeoff – but wouldn’t a hydrogen engine also be useable in a Martian environment? Could Blue have learned anything substantial from recovering the F1 engine last year or was it retrieved for non-technological reasons? Finally just out of curiosity, why is the Shepard stout thick and short in dimensions compared to typical rockets?

Thanks again for such a clear straightforward presentation.

JMJurist - May 10, 2015

Hydrogen engines can be throttled — space shuttle main engines are an example. Hydrogen is a mixed bag depending on specific choices. For example, it is roughly 150-250 deg F colder and 1/5 – 1/4 as dense as liquid methane . That causes more problems with boil-off while waiting on the pad unless the tank is insulated. My speculation is that New Shepard is “thick and short” because of tradeoffs involving hydrogen tank surface to volume ratio. Minimizing that ratio minimizes heat loss and tank mass as a fraction of the contained propellant mass. For a kerosene-based propellant or even for liquid methane, the heat transfer problem is not as much of an issue.

Yet, the higher specific impulse of hydrogen is also a consideration. For a two stage launcher to LEO with a 15 percent margin for gravity and aerodynamic losses, a hydrogen-fuelled launcher must have a propellant fraction of about 69 percent on the pad whereas a kerosene-fuelled launcher must have a greater propellant fraction of a little more than 80 percent.

Liquid hydrogen is more expensive than kerosene or liquid methane and more difficult to handle. Making methane from the Martian atmosphere requires hydrogen which could potentially be derived from in situ water. Various ways of accomplishing this are discussed in other venues.

To conclude, there are many tradeoffs to consider when deciding between hydrogen and an alternative for a propellant — several of which are mentioned above.

Thank you for the inquiry.

3. JMJurist - April 30, 2015

If you download the PowerPoint titled “Choices” and go to Slide 8 the address for the article in question is shown. Active linking is not enabled on the PowerPoint, but cutting and pasting the address into your browser will work. I last tested that approach on Wed Apr 28.

The address is also given below:
http://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html

4. Evon - April 29, 2015

Dr. John Jurist,

John I left this request on a different space show blog and then forgot some specifics about the request but this is what I remember: You mentioned a paper in relation to one of the slides, I think 8. I attempted to find the link to the paper but could not find it. The paper sounded interesting. Could you post a link to the paper here please? I will pick up the paper if you are able to parse this request.

Thank You
Have A Great DAY!!!!
Evon


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: