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ScienceIamA former NASA astronaut with 1000 hours aboard the Space Shuttle and a professor in MIT’s Department of Aeronautics and Astronautics. I'm Jeff Hoffman– Ask Me Anything!

Sep 20th 2017 by jhoffma1 • 20 Questions • 210 Points

THAT'S IT FOR TODAY. THANKS FOR ALL OF YOUR GOOD QUESTIONS. SORRY I COULDN'T ANSWER ALL OF THEM, BUT I HOPE THIS HAS BEEN INTERESTING FOR YOU.

PLEASE JOIN US FOR 16.00X - INTRODUCTION TO AEROSPACE ENGINEERING AND HUMAN SPACE FLIGHT, STARTING NEXT TUESDAY (26 SEPTEMBER).

AND REMEMBER THAT MITX WILL OFFER A NEW SPACE COURSE IN THE FALL OF 2018 - 16.885X - SPACE SHUTTLE SYSTEMS ENGINEERING.

SIGNING OFF!

I'm Jeff Hoffman - former NASA astronaut and current MIT Professor. In my spare time, I'm the director of the Massachusetts Space Grant Consortium and Deputy Principal Investigator of an experiment on NASA’s Mars 2020 mission.

I've logged 1000 hours of flight time aboard the Space Shuttle, spent four years as NASA’s European Representative, and joined the MIT faculty in August 2001.

My free Introduction to Aerospace Engineering course on edX begins September 26th.

I'd love to answer any questions you have about outer space!

AMA!

Here's my proof

Q:

Dr Hoffman, I watched your MIT Space Shuttle class (twice) and am very interested in space history (propulsion engineer!). Listening to you, Aaron Cohen and others, I've always wanted to ask this question: The Shuttle was a marvel that achieved all of its "technical" requirements, but failed to meet its flight rate and ease-of-reusability goals. At what point during the development of the system did the engineering team realize the shuttle wouldn't "work" in the sense of flight rate/reusability? What was the reaction of the program management? Was a decision ever conscientiously made to simply get the current design flying and try better the next time around?

A:

This is too complex a question to deal with simply. The Space Shuttle course is now being prepared as a MITx course which will be given in the fall of 2018. We will discuss this more fully at that time.


Q:

Seeing the Earth from up there and realizing what a rare thing our planet is, do you believe there are other planets that could support intelligent life? 

A:

There are so many planets in the universe that it is almost certain that life exists in many places. However, whether any other life forms have evolved into what we would recognize as "intelligent" is something we can only speculate on.


Q:

Hello! Here's Stepan, 22 y.o. from Czech Republic, STEM major. My question is...do you think that our generation will have better affordable opportunities to visit space? Now you have either be an astronaut or pay $20M to go to ISS. Do you think that Musk's $200K Mars-rountrip-vision is real? Do you think that Branson's project will be affordable? Thank you have a nice day!!

A:

For now space travel remains extremely expensive. SpaceX and Blue Origin are working hard to make it less expensive, but it will be a long process, and I don't know when space travel will become a reality for lots of people. Transatlantic airplane flight was extremely expensive when it first started, and it took several decades and the development of commercial jets to bring the cost down to where it is today.


Q:

Would you fly to space again (for example to the ISS) if you were offered to do so?

A:

I'd go in an instant (but please don't tell my wife, who is happy that I am not flying anymore!)


Q:

Hello Mr Hoffman. What do you think about plasma engine that Franklin Chang-Díaz astronaut has been developing?. They say it could take us to Mars in 40 days.

A:

I flew with Franklin twice, and I am familiar with his work. It is very exciting and has incredible promise if it can be proven to work. So far, he has made great progress. I hope to see a test of VASIMR on the ISS in the not too distant future. Improved propulsion is critical for our future in space, and this is one of the technologies that could provide this.


Q:

What significant breakthrough could we get in the field of aerospace engineering in the near future? What breakthrough would you like to see happen in the near future? What does being in zero gravity actually feel like?

A:

I think our two biggest needs are better propulsion (get to places faster) and protection against radiation.

Zero gravity is a real blast. It's a feeling of physical freedom like I never experienced anywhere else. I think it is so much fun that people will pay to experience it - space tourism.


Q:

Is it posible to become an astronaut at 40 Professor?

A:

There is no "official" age limit for astronaut candidate selection. NASA has selected a few astronauts in their early 40s. Other than John Glenn, who flew at 77, the oldest astronaut to fly was in his early 60s.


Q:

Aerospace Engineering and Space Craft Engineering - are they the same thing?

A:

Aerospace engineering is more general - it involves rockets, satellites, spaceplanes, etc. Spacecraft engineering would generally refer to satellites or planetary probes.


Q:

I currently work in IT with a BA degree in computer science. I'd like to take this edX course as a first step in transitioning to hard rocket engineering. What should my next steps be?

A:

Next fall (2018) MITx will have a new course that I am putting together on Space Shuttle Engineering. That would be a good start. However, if you are serious about a career in aerospace engineering, you need to consider a graduate program where you can get a masters degree. Good luck!


Q:

Dr Hoffman, what kind of material was used for the Space Shuttle thermal protection system? It was only ceramic materials or ceramics matrix composite with silica fibers?

A:

The tiles were ceramic. There were also thermal blankets on cooler parts of the shuttle and there was carbon-carbon on the hottest parts like the nosecone and wing leading edges. This will be covered in the fall 2018 MITx course on Space Shuttle Engineering


Q:

I signed up for the course. Any recommended pre-course studying?

A:

The course is self-contained, but the more you have read about space exploration and space travel, the more you are likely to get out of the course. I hope you enjoy it!


Q:

When have you noticed using electrical power as propulsion for the spacecraft during the flight?

Do you ever think that we can fly a spacecraft using electrical power as a main source of power for the engines to push towards electric mobility?

A:

Many small spacecraft (planetary probes) already use electric propulsion (i.e. ion drives). The problem is that they have low thrust, so they are not yet suitable for human spaceflight, where you want to get places as quickly as possible.


Q:

What would be your main piece of advice in terms of setbacks, for someone willing to become an astronaut Professor?

A:

Becoming an astronaut is a wonderful dream and can be very motivating, however the chances of selection are slim because so many people apply. For NASA's most recent selection, 18,000 people applied and only a handful were selected. So my advice when people ask me this question is that becoming an astronaut should be your "Plan B", and you need to have a good "Plan A". In other words, pursue a career in which you are interested and competent, and keep applying to the astronaut corps. Good luck!


Q:

Do you ever think ramjet technology can be made practical?

A:

I think you are referring to hypersonic airbreathing propulsion. Many countries are working hard on this. I am sure someday it will become feasible.


Q:

Dr. Hoffman, how long will be the travel from Earth to Mars?

A:

With current propulsion technology, about 8 months each way.


Q:

What does space food taste like?

A:

It's a lot like backpacking food. Mostly dehydrated or MREs. The Russians use a lot of canned food. It's pretty gooey. Your sense of smell is decreased in space, probably because of all the extra fluid in your head. NASA gave us lots of hot sauce to spice things up. When I got back from my flights, the first thing I wanted was a nice salad that was cruchy and I could chew on.


Q:

Do you think there is a future for Aerospace engineers, specifically propulsion engineers?

A:

Aerospace is a vibrant field, with lots of new technologies being developed. We desperately need better propulsion, but currently nobody seems to know how to do this.


Q:

I'm a sophomore majoring in aerospace engineering. What steps would you recommend taking to become an astronaut?

A:

Study hard, get good grades, and get a good job where you can distinguish yourself. If you are lucky enough to get selected as an astronaut, that's great. But if not, at least you will have a rewarding career.


Q:

Do astronauts train on the vomit comet? How does the vomit comet compare to space vs. the buoyancy lab? Thank you

A:

The 0-g aircraft produce real weightlessness, which is just like being in space, only for a very short time (20-25 seconds for each parabola). The neutral buoyancy lab is great for EVA training, but you are not really weightless.


Q:

I imagine that lots of stuff gets loose and travels around the cabin in zero-g, so my question is what's the most surprising thing you found floating in front of your face?

A:

The most surprising thing that anyone found floating in front of his face was, I think, his own hand! When you are weightless, you can lose track of your arms and legs if you are totally relaxed. A sleeping astronaut awoke to see a "mysterious hand" floating in front of his face. It took quite some time for him to realize that it was his own hand!