Solicitation for Consensus Body Members – Flight Vehicle Coordinate Systems, ANSI/SAWE STD A-6

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The second solicitation for Consensus Body members for development of ANSI/SAWE Standard A-6 has posted publicly at  ANSI Standards Action May 15, 2020, page 40. With a response end date of 6/14/2020. This is a Call for Members (ANS Consensus Bodies) notice for directly and materially affected parties who are interested in participating as a member of an ANS consensus body. You do not have to be an SAWE member to participate in this Consensus Body.

We are  particularly looking to achieve balance of the consensus body which is currently heavy with the category User-Government. Other categories are under represented and persons wishing to participate with one of those representations in mind are welcomed on a priority basis. Others are welcome to apply as well, The participatory categories are:

  • producer: the product design/developer typically the manufacturer of the product in question
  • user-industrial: Where the standards activity in question deals with an industrial product, such as steel or insulation used in transformers, an appropriate user participant is the industrial user of the product.
  • user-government: Where the standards activity in question is likely to result in a standard that may become the basis for government agency procurement, an appropriate user participant is the representative of that government agency.
  • general interest: where an overseeing interested party may participate or other possible participant not involved in producing, directly using, or acquiring the product as a government user

A current draft of the standard is available from the contact noted below:

SAWE (Society of Allied Weights Engineers)

Contact: Jeffrey Cerro, (757) 570-1386, jeffcerro@verizon.net;

NASA Langley Research Center, MS 451, 1 N. Dryden Street, B1209, Hampton, VA 23681

New Standard

BSR/SAWE STD A-06-202X, Standard Coordinate System for Reporting the Mass Properties of Flight Vehicles RP A-6 (new standard)

Stakeholders: Aircraft, space craft, launch vehicle developers, and users.

Project Need: The recommended practice needs to be updated to incorporate additional scope, update relevant aspects that have evolved since the last major update [1999], and also go through the ANSI process to provide accredited consensus across the industry. Specifically, the RP to be updated is to include the scope of inertia topics that have impacted the missiles and space industry in the past and possibly prevent possible issues in the future. Typically used coordinate systems have also evolved over time and the recommended references need to be expanded upon to be more relevant. Incorporating the proposed additional scope into the standard will allow mass properties engineers to reduce errors or technical challenges regarding inertias and also update the coordinate system and other reporting aspect to be more current with respect to daily practices in the industry.

This standard will provide coordinate system designations for flight vehicles and standards for the placement of flight vehicle mass, center of gravity, and inertia with respect to vehicle features. Launch, space, and atmospheric vehicles are included in this standard.

How much does the ocean weigh?

Quick – how much does the ocean weigh?

Let’s say you’ve recently been spending a lot of time at home with a small child. You foolishly told them you can’t play right now because you’re busy doing important work calculating the weight of stuff. This has sparked their interest. And they won’t let go of that question.

Sigh. I don’t know how much the ocean weighs. I couldn’t even guess how many zeroes are in the number.

Or could I?

70% of the Earth’s surface is covered in ocean. I’ve watched enough nature shows to remember that’s about right. What would that surface area be? Let’s assume the Earth is a sphere (it’s not, but it’s close enough). What’s the formula for the surface area of a sphere? I don’t remember and my Weight Engineer’s Handbook is in the office. No matter – let’s assume Earth is a cube instead. I know how to find the surface area of a cube.

I know what you’re thinking – working from home with a hypothetical kid asking dumb questions all day has driven me bonkers. We can’t assume the Earth is a cube. But for this estimate we can. All I’m looking for is a number within a few orders of magnitude of reality. The difference between a sphere’s surface area and a cube’s (with the cube’s edge the same length as the sphere’s diameter) is negligible.

The surface area of a cube is six times the area of one side of height H, or 6xH². Since our cube’s height is the same as our sphere’s diameter, we need to know Earth’s diameter. Because “Apollo 13” is an awesome movie I know that a spacecraft in low Earth orbit moves about 17,500 miles per hour and takes 90 minutes to complete an orbit. That gives a circumference of 26,250 miles and a diameter of 8360 miles. Let’s call it 8,000 miles because I read somewhere that low Earth orbit is about 50 miles up, the Earth is rotating under the spacecraft and I’m kidding myself if I’m going to assume any precision in this calculation.

That gives us an ocean surface area on our Earth-cube of 70% x 6 x 8000² = 269 million square miles.

I don’t know the average depth of the ocean, but I know most of it’s deep. I’m guessing between one and ten miles because I heard “miles” and ocean depth mentioned together somewhere. Let’s say two miles deep. That gives us a total volume of 538 million cubic miles.

Every weight engineer knows the density of water – it’s 1 gram per milliliter. That’s fresh water – salty ocean water is denser, close enough. I remember it that way because I’m an expatriate Canadian and the metric system is a tenacious thing. No matter, I can convert. There are 454 grams in a pound (thanks, Canadian food packaging!), a milliliter is the same as a cubic centimeter and there are 2.54 centimeters in an inch. Put that all together and you get a water density of 0.036 lb/in³, or 9,181,017,236,653 pounds per cubic mile. Time for scientific notation: 9.2x10E12 pounds per cubic mile.

At a volume of 538 million cubic miles, our ocean weighs 4.9x10E21 pounds.

How did I do? According to the internet, “Earth’s ocean is made up of more than 20 seas and four oceans, weighing an estimated 1,450,000,000,000,000,000 short tons” – or 2.9x10E21 pounds.

There you go, kid. My estimate came within 2x the real value. That’s pretty good for starting out with no earthly idea!

This is called “Fermi approximation”, named after World War Two-era physicist Enrico Fermi, who was known for making good approximate calculations with little to no data. It’s a great way to get a quick rough guess before moving on to more precise methods.

My first boss when I was a brand new mass properties engineer used this method to devastating effect. He would send me off to spend days researching, interviewing designers and analysts, drawing sketches and running calculations to estimate the weight impact of a potential design change. When I returned, he would knock off an estimate in a few seconds that would invariably be within spitting distance of my hours of work. It was humbling, and I would ask him why he made me go to the effort. He’d say his method is quick, but now I have the data to back it up. He didn’t say it also made me a better mass properties engineer, by giving me a powerful tool to quickly understand the size of a thing, whether it’s a potential weight impact or the number of hours a task might take – or the answer to a childish question.

If you like hearing about the techniques, methods and experiences of other weight engineers, I encourage you to attend the 2020 SAWE Tech Fair, starting June 22. A wide range of technical presentations, industry seminars and training classes will be featured, all live and online, presented by your mass properties colleagues.

SAWE TECH Fair and Training – Save the dates

The first ever SAWE TECH Fair and Training will start June 22nd and run over a three-week period.  The first week will focus on Technical Presentations.  The second week will focus on Standards & Practices with two joint sessions and the Industry Committee workshops.  There will be five training courses filling out the schedule.  Also, we’ll have presentations from our SAWE exhibitor and sponsor community to update us on their latest products.

The detailed schedule and pricing will be finalized soon.  But we want to share that the TECH Fair will be a great opportunity at very good price.  In addition, we’re working the schedule to have a minimal impact on workdays.  The SAWE TECH Fair and Training will be a good value for your training budget.

I urge you to make plans to participate and please spread the word.

Here’s a preliminary line up of what’s coming at the online SAWE TECH Fair and Training.

Live, Online SAWE Training Courses to be offered

  • Automated Weight and Balance System (AWBS)
  • Designing the Aircraft of the Future
  • Marine Vehicle Weight Estimating Methodology
  • Structural Weight Optimization for Mass Properties Engineers
  • Developing Basic Parametric Methods

Technical Presentations Planned

  • Keynote Address:  Dr. Dan Raymer of Conceptual Research Corporation “Why Weight Engineers are So Dang Important, and Why Weights Engineers Get All the Blame”
  • Weight and Balance Challenges for Hybrid Electric Propulsion System
  • Hydrogen Fuel Cell Power System Weight Challenges in VTOL Aircraft
  • Folding Wings – Benefits in Aircraft Design Despite Local Mass Increase
  • Use of Mass Growth Allowance to Dynamically Manage Mass Risk
  • Rotorcraft Mass Assessment in an Integrated Design Framework
  • Development of the Mass Properties Certification Program
  • A Portable Device for Measuring the CoG: Design, Error Analysis and Calibration
  • Investigation of an On-board Weight and Balance System for a Helicopter Equipped with Skid Landing Gear
  • Theoretical and Experimental Evaluation of the Flexibility of the Test Rig on Inertia Property Measurement
  • Aft Perpendicular… an Afterthought
  • Finding the Balance Between Accuracy and Practicality In Deadweight Audits
  • Dynamic Computer Simulation of Aircraft Buoyancy
  • Class II & 1/2 Mass Estimation of Light Aircraft Composite Wings
  • CFRP Density Uncertainties and its Overall Mass Impact
  • Strategies for the Composite Stiffened Panel Topology Optimization for Minimum Weight
  • One fits all? A Comparison of Weight Estimation Methods for Preliminary Aircraft Design
  • Evaluation and analysis of applying a MBSE Approach for optimizing Mass Properties Parameters in Commercial Aircraft Design
  • Advanced Weight Forecasting Based on Physical/Mechanical Similarity of Components During Early Development of Land Vehicles, Aircraft and Spacecrafts
  • Forum discussion topic:  The Role of Statistics in Mass Properties Engineering

Standards & Practices

  • Status of Recommended Practices
  • Overview of Recommended Practice development process
  • Certification Development Participation and Review
  • Discussion of development of a standard passenger weight guideline for the FAA as a standard practice for airline usage
  • Review of RP’s A-7 and A-8
  • Military Aircraft Workshop (agenda pending)
  • Marine Workshop (agenda pending)
  • Missiles & Space Workshop (agenda pending)
  • Offshore Workshop (agenda pending)
  • Ground Vehicle Workshop (agenda pending)
  • Airline Affairs Workshop (agenda pending)