katdude

This just adds another layer to the question. Chemical energy in each burn is converted to light, heat, kinetic energy of the particles you mentioned, and kinetic energy of the model spacecraft. The kinetic energies imparted to the spacecraft each time in opposite directions cancel out as final kinetic energy of it is zero. So the question is still valid. Other way to put it: If energy is non-directional, how can kinetic energies imparted by thrust in opposite directions cancel each other? Earth is supposedly a sphere. And men supposedly walked on the moon. lol

@MilitaryToFinance I have studied all those metrics you mentioned before. I was doing great, in $6k profits over just 4 months by trading high yield dividend stocks that are close to book value and currently on an uptrend. Now I messed with growth stock, FB in August. I bought it the day before it crashed thinking "Well, FB had great earnings results each quarter for the past 3 years, I can sell it off after the results". Now I'm sitting at over $18k loss. That's what happens when you pay for projected growth, earnings, etc blah blah all those metrics. I think you should pay for what its worth now, not what it may be worth in the future. Because expectations can change and that's what happened to FB. On the other hand, if I stuck on to my prior strategy of trading stocks close to blook value that have strong fundamentals, pay good dividends and are on uptrend, I would have still been in profits. Amazon's earnings per share are $12 and Facebook earnings per share are $6. How come Amazon is $2000/share and Facebook is $160? Amazon should only be double the price of FB as it only earns double?? Thats why I say price is psychological and just BS. Pay for what its worth and you won't lose in the end.

@Klepto Agree with the points you made. However the question still stands even on earth’s surface. Lets say you’ve built a huge room in a lab and managed to suck out all the air in it. There’s a very long absolutely frictionless horizontal table in this room. Now apply the above question to this scenario. A model spacecraft is stationary at one end of the table. Now it does Burn 1, accelerates toward other end of table till it reaches velocity v. After traveling distance d, it does a Burn 2 in opposite direction and comes to a halt. If we think the chemical energy in fuel used in Burn 1 is converted to say 90% thrust derived kinetic energy, 5% light and 5% heat energy, and same thing happens with Burn 2. Accounting for the light and heat energy loss in both burns, it seems the 90% thrust derived kinetic energy from Burn 2 cancelled the kinetic energy from Burn 1 because it was in opposite direction. Agree that due to the reduced weight of model spacecraft after Burn 1, you will need to expend less fuel energy in Burn 2. So Burn 1 energy is greater than Burn 2 energy. But 90% of Burn 1 energy and 90% of Burn 2 energy created thrust derived kinetic energy which ultimately cancelled each other. How can this happen? Can energy be cancelled because of opposite direction? So energy is not a scalar? There was a net loss of chemical energy stored in the fuel as it was used up, and I don’t see it converted into anything else apart from the small heat and light energy, so energy can be destroyed.? Any aerospace/ aeronautical engineers on this forum? Any takers?

My free unsolicited words of wisdom regarding stocks.. - Never invest all your money in one stock. Diversify. If you have $100, put $20 each in 3 stocks, put $40 in bonds, etc - The price of a stock will be what most people think its should be, for whatever reason. Amazon may not actually be worth $2000/share, but it’s trading there because that’s what people think it’s price should be. - Price is psychological, not based on the actual book value. Invest in stocks that are trading close to what their book value is. Selling all Amazon assets and properties and distributing them to shareholders will not get you $2000/share. You will not get your money back. - Because when the time comes, price bubbles burst and you don’t want to loose a ton of money!

@Klepto It is well known that more energy is needed to decelerate a spacecraft. Space shuttle needed to do a de-orbit burn in order to reenter earth's atmosphere. There is a net energy loss because the fuel has been used up and the final kinetic energy is still zero in our scenario. @PilotCandidate Well some chemical energy of the fuel is converted to light energy and heat energy but majority of it is used to thrust the spacecraft and impart kinetic energy to it. Similar to how jet engines impart thrust. I honestly think this question is what is preventing us from creating spacecraft that can dart from planet to planet at incredible speeds. In other words, we will truly have the SPACE FORCE that Mr. Trump wants.. haha.. Star Wars for real! and American will be the first human to set foot on Mars!!

So.. many of you guys here are pilots.. and I am guessing many know energy management principles from fighter training. From Wikipedia.. And you know that kinetic energy of a moving body is 1/2 x m x(v squared), where m is mass of the body and v is velocity. Imagine you are in a spacecraft in outer space, beyond the galaxy.You are observing another spacecraft that is quite close to you and has no relative motion with respect to you. These two spacecraft are the "isolated system" and are free from any outside gravitational influences. Now let's say the other spacecraft fires its engines (Burn 1) and accelerates to velocity v with respect to your spacecraft. Then the engines pause. After it travels a distance d away from your spacecraft, it fires its engines in the opposite direction (Burn 2) and decelerates to having zero velocity with respect to your spacecraft. So let's say the chemical energy in rocket fuel is converted to kinetic energy after Burn 1. But after Burn 2, more fuel and thereby chemical energy is expended but is used up to decelerate it back to zero velocity. After Burn 2, the spacecraft has zero kinetic energy and also a net loss of chemical energy. Where did this chemical energy go? Energy is said to be a scalar quantity that has no direction, so how was the kinetic energy in one direction cancelled by kinetic energy imparted in other direction? Where did this kinetic energy go? So energy can be destroyed?? Appreciate any takers.. Thanks in advance!

Thanks for the advice, @FlyArmy !! I think I want to give my best shot at getting selected for UPT, given that I'm 30 years old. So I've decided to fly those 23 hours and get PCSM upto 82. Agree that most fighter units hire young dudes with PCSM scores over 90. With a score of 82 I'm thinking I should have a decent chance of making the cut for a Reserve heavy squadron and get ETP. Timing and luck of course are crucial at UPT. If someone washes out from T-38s, etc for whatever reason and they offer me a fighter, I'll take it. If getting a fighter means going AD from Reserve, I'll do it. Instead, if I suck at UPT or just turn out to be plain unlucky, I'm perfectly fine with moving on to T-1s and then my heavy airframe. Heavies have their own mission which is very crucial to overall success of the Air Force. For example, fighters run out of gas very fast and they need tankers to loiter, etc There's no bad flying job in the Air Force in the end. Endless opportunities like Pilot-Physician, Astronaut, Test Pilot, etc exist but will my timing and luck help me is the question. I guess I'll find out at UPT once I get past this ETP obstacle.

@FlyArmy Congrats on making it to fighters after a long wait! I am currently enlisted in the Army Reserve so I'm making the switch like you and hoping to make the cut. I am in touch with the Pilot/Physician program, and for whatever reasons (AD not doing Age waiver/ETP, etc..), I can't join it directly right now. But once I get to UPT, and if I'm allowed to go Active Duty, joining that elite program is a possibility. Test Pilot School and Astronaut candidate training are further down the road, but once again I believe the opportunities are better for the Active Duty folks. Active Duty Test Pilot would be an awesome job! And perhaps help toward getting an Astronaut slot. I just got my PCSM score, it is 77. It says I can bump it up to 82 if I get my flight hours to 201 or more from my current 178 hours. Do you guys think 82 makes a big difference in selection versus 77? I am willing to drop the $2500 needed to fly 23 hours more if it is really worth it. PS: I have been taking the trash out, cleaning floors, etc at my current unit from the past 3 years haha.. I know its part of military life, but the fact that @hindsight2020 denied me even that privilege made me think what I was doing wrong.

@hindsight2020 You seem to be quite knowledgeable, thank you for your input on the matter. I didn’t know that it's 11F rated O4 and higher ups that are short. I am in no way making demands, I am just saying I won’t let it go if they offer fighters. If you scroll up, you can see that I mentioned I am totally fine with serving in a heavy unit. Agree that it is timing and luck. I know I am late to the party, but I only got my citizenship and LASIK done very recently. I have always dreamed of fighters and would have loved to be that 18 yr old kid you mentioned. But please understand not everyone can be that kid who’s 22, fresh out of college and eligible to join. ETP is there for a reason, to give someone a chance when AF finds the circumstances reasonable using the whole person concept. I see that you’ve contributed a lot to this forum, but honestly find your comments about taking trash out quite condescending and disturbing. When I said I’d love to train on many airframes, I meant trying for a job like Test Pilot. And you can’t do such jobs being in the Guard. I am not a narrow minded person that you have imagined. PS: I did go to medical school and have a license to practice medicine in US. I am still not rich enough to buy a L-39. Lol. And I would take the trash out if you hook me up with a fighter unit 😉

I feel like Guard is restricted in growth potential. Once you train on one airframe you pretty much serve with that unit and location for a long time. It gives stability for people who desire it. However, it doesn’t offer the potential of growing to be a General level officer of the Air Force. I like to train on multiple airframes and perform in a variety of settings. Agree on your views with ETP, it may be more unit specific and how much they like you. And casting a wide net doesn’t hurt. Though switching from Guard to AD/RC may be tough down the road. Like I said I would be fine switching to AD during UPT should they offer me fighters. I can’t join AD now as I believe AD doesn’t do Age waivers/ETPs for fighter pilots. https://bogidope.com/article/age-old-question So only Reserve and Guard units do age waivers/ETPs.

No offense to any Guard member, but I don't like the idea of restricting myself to one state while at the same time taking extra obligations for that state. I'd like the flexibility to be able to move to any state. Besides my recruiter is for AFRC and he won't like me switching. That said, it would be awesome if a Guard fighter unit does ETP. I find the process for Guard fighter units more competitive and expect them not to do ETPs any more than the Reserve units.

Absolutely understand and agree with you guys, @ssup and @FDNYOldGuy. Thanks for the input! I appreciate the hard work a heavy unit has to put in to get my ETP approved. I have no problems sticking with them. However should I have a chance at fighters, I don't want to let it go. My understanding is that there are 6 AFRC fighter squadrons, out of which, two fly the F-22. Those two don't get funding for the B-course, so they can't hire candidates that need to go to UPT. Out of the rest, three fly F-16C and one flies F-15E. After talking to a current fighter pilot at one of these units, it is very very very hard to get them to do an ETP and sponsor even some one like me who has been in the Army Reserve for 3 years. Most of their spots are staffed by pilots getting off Active Duty for the airlines but who still want to fly in a fighter cockpit occasionally. Obviously if I can get one of these 4 units to do an ETP that would be my first priority. These units are also at different phases of utilizing their UPT funding so they may have hired a bunch of dudes recently and not hiring any time soon. On the other hand, heavy AFRC units are much in need of pilots and they are currently doing ETPs frequently. Also consider that Active Duty Air Force is currently over 1000 fighter pilots short, so they need them badly. If one of the four AFRC fighter units is willing to take me over from the heavy unit during UPT, I'm gonna do it. Also should the possibility arise during UPT that they can offer me fighters if I can switch to Active Duty, I'm gonna do it. If not, I will finish assigned heavy track and continue with the Reserve heavy unit. I do feel bad to do abandon the heavy unit, but it is not our fault. There's people who want fighters but can't get there because of age, it the system in place that creates these possibilities. In the end, it's all for the greater good, and the Air Force will use us in spots where there is the greatest need. Good luck to you guys!

I was applying to the AFRC unsponsored board when my recruiter said his superior told him that I can't apply go the unsponsored route as I need an age waiver/ ETP. I'm 30 years old. Can you please give me the contact information for the recruiter that said they'll do age waivers for unsponsored applicants? I can put my recruiter in touch with him/her. As of now, I'm hoping to get picked by one of the heavy units to go to UFT as they do the age waiver paperwork. I want fighters too. I'm hoping perhaps I can switch units or go Active during UPT if that can lead me to fighters. This seems to be the only way I can get to fighters as I believe Active Duty doesn't do age waivers. My AFOQT pilot score: 86, Awaiting TBAS/PCSM, Flight hours 178.3