NASA Releases Asteroid Redirect Mission Broad Agency Announcement
NASA to Host Media Teleconference on an Asteroid Initiative Broad Agency Announcement
“NASA will host a media teleconference at 3 p.m. EDT Friday, March 21, to discuss the same-day release of its Asteroid Initiative Announcement of Opportunities.”
NASA Asteroid Redirect Mission Broad Agency Announcement
“NASA intends to issue has issued an Asteroid Redirect Mission Broad Agency Announcement (BAA) on March 21, 2014. NASA is developing concepts for the Asteroid Redirect Mission, which would use a robotic spacecraft to capture a small near-Earth asteroid, or remove a boulder from the surface of a larger asteroid, and redirect the asteroid mass into a stable orbit around the moon. Astronauts aboard the Orion spacecraft launched on the Space Launch System would rendezvous with the asteroid mass in lunar orbit, and collect samples for return to Earth.”
Could someone provide a summary of the Asteroid Initiative media teleconference? Scanning through the released BAA PDF document, the funding available is not much, even for NASA standards. $6 million. The largest individual award is just $500K. So as the document makes clear, this is early concept work. The early funding levels are so low and it ensures that the ambitious time-line for the Asteroid Initiative is null and void. Interesting that Dr. Green is listed now. I recall that in the first Asteroid Initiative public conference at HQ, he could be seen behind the seating, pacing back and forth.
I like everything about the Asteroid Initiative except its use as a means of satisfying the mandate to send humans (astronauts) to an asteroid by 2025. It does not justify completion of SLS and Orion and it is not a good driver for the R&D needed for beyond Earth orbit (BEO) human exploration.
What I would suggest to Dr. Green et al. is the following: 1) Scale down the mission to retrieve a 5 meter (16 ft) asteroid, a size still detectable for selection purposes and also very abundant.This reduces the mass by a factor of 4.5 and brings the capture mechanism within the range of a 5 meter fairing. Overall the cost of the mission shrinks by reducing demands on solar-electric propulsion, the potential to use a much lower cost launch vehicle and also simplifies other obstacles such as de-spinning the rock, grabbing or bagging it. 2) Maintain the facade that this will provide the means to satisfy the Obama’s initiative to visit an asteroid. In 2 years and 10 months, this mandate will be dropped. NASA will be left with some progress in developing the Asteroid Retrieval Mission but can then look at it as purely a robotic mission. The smaller design will satisfy technological objectives and science objectives which can continue with follow-on missions using Nano and Micro-Sat probes to the rock in a Lunar or E-M Lagrange point orbit. A small rock, be it 5 meters or 8.2 meters will serve this purpose. Additionally, the 5 meter rock delivered at low-cost, will serve as a testbed for private industry – to rendezvous and engage the object and test methods. The smaller less expensive rock could still serve as a rendezvous point for astronauts to test extra-vehicular capabilities as part of missions to Circum-Lunar and E-M Lagrange points, primarily testing long duration habitats and propulsion systems. (5 meters will still make great postcard photos of an astronaut floating beside an asteroid)
According to the PDF there are two concepts they are looking at, one is for capture of a 4-10m asteroid, but they are also interested in hearing proposals for capturing a boulder of 1-5m in size from a larger asteroid, which is in line with the size that you are recommending. Seems that they are not interesting in having the robot break off a chunk of an asteroid, but merely to snag a loose boulder from the surface.
Again i feel it makes more sense to return the asteroid to the ISS where it can be studied at leisure. This will save well over $1B in mission cost and provide much more time to study the specimen. Once examination is completed the material can be applied to some of the modules as radiation shielding.
That will add several years to the length of the mission. EML-1 to LEO has a delta-V of 7.0 km/s when using low thrust. The asteroid will be heavy.
I’m not sure adding a few years to the mission wouldn’t be a good investment. However
http://www.nasa.gov/pdf/740…
gives a return time of only two years for a 500 ton asteroid. I’m curious what thrust, power and delta v are assumed for the SEP drive.
The are talking about a machine with a mass of 13,000 kg, having a 30kW – 50kW power system whose ‘n’ engines are 10 kW-class electric propulsion. The Isp is 3000 s and the mission delta-V is 10 km/s.
http://www.nasa.gov/sites/d…
How many newtons total thrust? for 50Kw one would expect 2-3N total for Busek type hall effect thrusters. For a 500 ton asteroid this would give an acceleration of
4 x 10^-6 m/s^2 by my wag. Is the 10 km/sec for the asteroid or just the probe going both ways? If the former it would take 30+ years for this delta v. Of course Vasimir has more thrust but lower ISP.
NASA is not advertising the thrust produced by its new EP thruster. The 10 km/s delta-V will be the propellant loaded at launch.
Hard to know what to make of it; delta V before the capture is easy. After the capture it is a different kettle of fish entirely. However if it were 5 km/s after capture for the proposed 500 tons, that would still take 15+ years, not the two years advertised. So I would guess they are planning on something closer to 70 tons, for a diameter of ~4m, which would just fit inside the pressurized hangar module once proposed (and still needed) for the ISS. We could almost fit it into the PLM if the ground loading hatch could be opened. If it were _inside_ the ISS (under normal atmosphere but zero G) imagine how much easier it would be to study than in lunar orbit, there would be _no_ increase in ISS drag and no one would worry about it “falling”.
That would add some cost of ownership as ISS is very low; its mass will contribute to the cost of boosting ISS and controlled disposal.
Adding mass to the ISS would not add to the reboost energy, as the increased mass would reduce the rate of deceleration due to aerodynamic drag. The energy required to maintain orbital altitude is equal to the drag force times distance traveled.
Aha, duh, mi scuzi. Thank you.
Huh?
http://en.wikipedia.org/wik…
The Tsiolkovsky rocket equation applies to vehicles which are accelerating without drag. Effectively the ISS is not accelerating at all, it is using thrust to overcome drag and maintain a constant angular momentum. The change in velocity the ISS will experience when a given impulse is applied is inversely proportional to mass, however the change in velocity the station will experience due to the constant force of atmospheric drag over time is also inversely proportional to mass, so the required impulse to maintain altitude is unchanged. More precisely, depending on how the asteroid is anchored, there would be a slight increase in drag due to any increase in projected fontal area in the direction of motion, but this effect is independent of mass, and with the immense span of the solar panels and modules the presence of the asteroid would affect overall drag only slightly.
We were talking about reboots energy requirements weren’t we? The ISS does not use thrust to overcome drag. The ISS uses Control Moment Gyros to induce a Torque Equilibrium Attitude which balance the force of gravity with the drag. Thrusters desaturate the CMG as necessary. The effect of the aerodynamic drag results in a decrease in orbital altitude which, below a certain limit requires a reboosts to maintain a nominally circular orbit of higher altitude. This reboosts “energy” is directly proportional to the mass and altitude. More mass = more “energy” required.
http://code.google.com/p/vi…
I agree thrusters are used to desaturte the CMGs, however the torque that is applied to the station is due to the assymetrical effects of drag and not dependent on mass.
Similarly, aerodynamic drag exerts a constant force on the station which opposes its orbital motion, causing its kinetic energy to decrease. Since Force = mass x acceleration, if mass is increased, acceleration is decreased. Double the mass, and atmospheric drag would cause only half the change in velocity. The orbit will only decay half as fast. Applying the same impulse with thrusters to correct orbital altitude would also produce half the previous change in velocity, but it would compensate for the energy lost due to drag.
Should we imagine the headlines? if you think the crazies came out with deep space plutonium sources, moving a space rock into earth orbit will not be understood. “What If It Falls?” or “Chicken Little! “It’s TRUE!”
A good point, but the ISS itself is actually a greater hazard since large pieces will hit the ground intact. The asteroid (unless a solid nickel iron specimen is located) would break up at altitude.
While I am very much in favor of this mission conceptually, I think NASA is once again making two of its most common fundamental mistakes.
First, they are cramming way too much into a single program. In a viable program you end up having one or more items that define your critical path. In this case there are going to be multiple critical paths, which guarantees that there are going to be continual program delays and cost overruns.
Second, they’ve thrown in money allocations, on which many decisions will be based, before the concept details are at all worked out. Right now, it’s all still at the requirements stage. So, the money amounts listed really mean nothing and it will all have to be done again.
I certainly don’t have the wisdom and experience of the senior people at NASA, but these mistakes seem absolutely obvious to me, so I’m really puzzled as to why they keep making them. It’s almost as if they plan to fail.
Finally, everything considered, tying SLS and/or Orion directly to this program is a huge mistake. The reasons why should be obvious to everyone by now.
This is not even requirement phase, it is concept phase but as you have stated, its a complex mission concept with distinct challenging activities. But how does it compare to say, MSL? Probably about the same, some unique first-try technology – capture/despin and SEP for return to Earth of a large mass. MSL had untried technology. SEP’s despin and capture (not necessarily in that order) of the asteroid is the challenge. There are unknowns which make it overall more challenging than the MSL “Skycrane” approach. With MSL’s EDL, some critical problems were well understood – the atmospheric model and the execution needed to perform the Entry and Descent phase. ARM’s challenge and MSL’s are technically like apples and oranges but I’d say, give the edge to ARM because of unknowns. I’d agree that the funding is a problem. They don’t have the funds to address the problems adequately. As the Brooklyn Dodgers would say, “wait until next year”, “wait until next general election”, this season is already over.
NASA need to drop the idea of capturing an asteroid and start putting some thought, money and engineering into capturing the space garbage in low earth orbit. It seems to me that this would be a much more pressing and worth while endeavor to pursue.
ANYthing we do it space is good- with the proviso that incremental technology capability is part of the picture. We can’t live in space without the ability to control the neighborhood- to cut the grass, so to speak.
My feeling is that The Powers That Be have decided on this one (possibly after choking on all the long poles and unknowns inherit in Mars-2021).
It will be interesting to see exactly how the plans for this one pan out. I don’t think they can get the asteroid back to EML-2 in time for the scheduled EM-2 in 2021; possibly in time for EM-3 in 2025.